Suchergebnisse

Visible light communication systems can be used in a wide variety of applications, from driving to home automation. The use of wearables can increase the potential applications in indoor systems to send and receive specific and customized information. We have designed and developed a fully organic and flexible Visible Light Communication system using a flexible OLED, a flexible P3HT:PCBM-based organic photodiode (OPD) and flexible PCBs for the emitter and receiver conditioning circuits. We have fabricated and characterized the I-V curve, modulation response and impedance of the flexible OPD. As emitter we have used a commercial flexible organic luminaire with dimensions 99 × 99 × 0.88 mm, and we have characterized its modulation response. All the devices show frequency responses that allow operation over 40 kHz, thus enabling the transmission of high quality audio. Finally, we integrated the emitter and receiver components and its electronic drivers, to build an all-organic flexible VLC system capable of transmitting an audio file in real-time, as a proof of concept of the indoor capabilities of such a system. ; This Project was funded by Comunidad de Madrid through the SINFOTON-CM Research Program (S2013/MIT-2790), and the Spanish Ministry of Economy, the Agencia Estatal de Investigación and European Union's FEDER through the TEC2016-77242-C3-(1-R, 2-R and 3-R) AEI/FEDER, UE Projects.

Mención Internacional en el título de doctor ; The world is going through constant technological changes, and what it seems to be a great improvement to the life in Earth at one moment, can lead to disastrous effects in the future. This has happened several times during the human being history, and one clear example is the climate change, global warming, and greenhouse effect. Since the industrial revolution, the humanity went through several technological changes: some of them allowed us to progress as a civilization, but others will lead us to self-destruction. A recent example is the release of chlorofluorocarbon (CFC) gases that destroyed a huge part of the ozone layer at the Earth's poles. Nowadays, one of the big problems that we are facing is the massive amount of carbon dioxide that we are throwing into atmosphere, mainly due to the energy generation activities. That is why this thesis is focused on increase the efficiency of devices that produce energy in a cleaner way, using solar energy. Doing so, in a near future we will be able to replace the actual contaminating energy sources for cleaner, non-emitting, renewable energy sources. Of course, this topic is too general, so this work is split in three big sections, intending to give full coverage to the topic. The first section is based onto the building blocks of solar harvesting, i.e., the solar cells. The more mature technology, commercially available is the silicon-based solar cell, but in the last years, a lot of technologies were also developed such as organic photovoltaics or perovskites. Each of these technologies have their own fabrication procedure, being the silicon very expensive and high energy demanding, while in the case of organic or perovskite the fabrication procedures are usually solvent-based and cheaper in terms of energy and material costs. After a brief explanation of the most used thin-film deposition techniques (used on organics and perovskites) the building process of a methylammonium lead iodide perovskite is explained step by step. This fabrication gave a resulting solar cell with a power conversion efficiency of 16.9%. Due to the environmental issues that this novel material can cause (mainly because it has lead in its composition), a lead-free perovskite was also studied (cesium tin iodide). The conclusion extracted from this study is that this lead-free perovskite could have very interesting applications, for example in smart windows, but their electrical conductivity problems should be solved first. Ending with this section, a proof of concept including organic and perovskite photodetectors into a visible light communication system was carried out, resulting in both technologies being able to perform good enough to be part of an audio link (with a bandwith higher than 40 kHz). Once we have a device to work with, in order to stablish their properties, it should be characterized. That is what the second section is about. This characterization must be done in a standardized way, under certain conditions and circumstances. One of these conditions is to have a stable, well-defined illumination source, that can recreate the standard AM1.5G spectrum (which is the spectrum of light that arrives at the Earth's surface, coming from the Sun). All this restrictions and parameters that dictates whether a light source is valid for this process or not are defined by the International Electrotechnical Commission under the standard IEC 60904-9. During this thesis, due to the necessity of this light to characterize devices, we decided to create one. This gave birth to SUNBOX, our proprietary solar simulator. SUNBOX belongs to a AAA-Class according to the IEC standard, which represents the highest quality possible in solar simulators. It is fully based on light emitting diodes and also customizable, with a tunable spectrum that can go from 0.2 to 1.2 suns and has 14 different wavelengths that can be intensity-tuned freely. It is also clearly distinguishable from the commercial ones because its structure is 3D-printed, so it is lightweight and has a low cost. Due to the intellectual property protection as a utility model, only a brief part regarding the electronic design is explained in this document, together with the calibration procedure that was carried out in terms of spectral match, homogeneity, and temporal instability that qualifies SUNBOX as an AAA-Class solar simulator. At the end of this section, some characterizations made with SUNBOX are shown, using different functionalities, to obtain key parameters in different types of solar cells. The characterization methods that were used, such as I-V curves or spectroscopy impedance are also explained along the document. Finally, in the third section, other approaches to improve the efficiency of the devices were studied, based on the optical treatment of light (light management). This management lies on the ability that some materials have to interact with the incident light, mainly in the form of nanoparticles, nanorods, or small gratings. Using a Finite Element Method simulation software (COMSOL® and JCMSuite®), several results were obtained remarking the importance of the inclusion of a nanostructure inside a device, increasing the amount of photogenerated current by 40% in a hydrogenated amorphous silicon-based device and by 20.5% in a perovskite/silicon tandem solar cell. Furthermore, preliminary results were obtained applying a nanostructure into a deep ultraviolet light emitting diode, that went from a light extraction efficiency value of 4.57% to around 15%, thus, multiplying by three the amount of extracted light with the same electrical power consumption. In summary, the main conclusion of this work is that it is possible to increase the efficiency of actual devices by and important factor and that there is a lot of room for future improvements. A boost in efficiency can be applied not only using novel materials with better electrical and optical properties, but also optimizing the devices that exist nowadays using light management techniques through the inclusion of nanostructures inside these devices. This has been demonstrated during this work using both approaches: the material science, creating a novel material with a cutting-edge fabrication method, unraveling the properties and applications for this material; and the photonics science, simulating the response of the device with the inclusion of a nanostructure in it, showing an outstanding improvement in all three study cases. ; El mundo actual está constantemente sometido a cambios tecnológicos, y lo que en un momento pudo ser un gran avance para la vida en la Tierra, puede ocasionar efectos desastrosos en el futuro. Esto ha ocurrido en varias ocasiones en la historia de la humanidad y claros ejemplos de ello son el cambio climático, el calentamiento global y el incremento del efecto invernadero. Desde la Revolución Industrial se han producido diversos cambios y avances tecnológicos muy importantes para la sociedad: algunos de ellos nos permitieron avanzar como civilización, pero otros nos dirigen hacia nuestra propia autodestrucción. Un ejemplo reciente podría ser la emisión de los llamados clorofluorocarbonos a la atmósfera, unos gases que destruyeron la mayor parte de la capa de ozono en los polos de la Tierra, ocasionando que una gran parte de radiación solar incidiera en los glaciares polares, incrementando la fusión de ellos y con ello contribuyendo al peligroso deshielo polar. Hoy en día, uno de los grandes problemas a los que nos enfrentamos es la gran cantidad de dióxido de carbono que estamos vertiendo a la atmósfera, principalmente debido a las actividades de generación de energía. Por ello, el objetivo de esta tesis está centrado en incrementar la eficiencia de los dispositivos capaces de producir energía de una forma más limpia, usando la energía solar. De esta forma, en el futuro cercano seremos capaces de sustituir las fuentes de energía contaminantes que usamos actualmente por otras fuentes de energía mas limpia, renovables y que no emitan gases. Cierto es que este tema puede parecer prácticamente inabarcable, y por ello se ha dividido este trabajo en tres secciones principales que se estudian en detalle, para dar cobertura completa a todo el tema. La primera sección está basada en el estudio de las unidades básicas de la recolección de energía solar, las celdas solares. La tecnología más madura comercialmente disponible es la celda solar basada en silicio (tanto monocristalino como policristalino), pero durante los últimos años se han desarrollado otras tecnologías tales como las celdas orgánicas o de perovskita. Cada una de estas tecnologías tiene su propio procedimiento de fabricación, siendo las basadas en silicio las más caras de hacer debido a su procesamiento y a la gran cantidad de energía necesaria para su refinado. Sin embargo, en el caso de las celdas orgánicas y de perovskita los métodos de fabricación están basados en solventes y deposiciones de líquido en capas delgadas, lo que las hace mucho más económicas en términos de materiales y de consumo energético. Después de una breve explicación de las técnicas de deposición de lámina delgada más usadas (aplicables tanto en orgánicas como en perovskitas), se explica el proceso de fabricación paso a paso de una celda solar de yoduro de metilamonio plomo. Esta fabricación dio como resultado una celda solar con un valor de eficiencia del 16.9%. Debido a los problemas ambientales que puede causar este material (ya que contiene plomo, altamente tóxico), durante este trabajo se estudió también una perovskita libre de plomo (yoduro de estaño cesio). La conclusión principal extraída de este estudio es que esta perovskita libre de plomo puede tener aplicaciones muy interesantes, tales como ventanas inteligentes debido a su transparencia, pero sus problemas de conductividad eléctrica deben de ser resueltos en primer lugar, para conseguir un dispositivo eficiente. Para finalizar esta sección, se llevó a cabo una prueba de concepto que consistió en introducir fotodetectores orgánicos y de perovskita en un sistema de comunicación por luz visible (VLC), comprobando que ambas tecnologías respondían de forma correcta para formar parte de un sistema de transmisión de audio (su ancho de banda era superior a 40 kHz en ambos casos). Una vez se dispone de un dispositivo funcional, para poder determinar sus propiedades internas, se debe caracterizar. En esto consiste la segunda sección. Estas caracterizaciones deben hacerse siguiendo los estándares correspondientes, bajo ciertas condiciones y en unas circunstancias determinadas. Una de estas condiciones es tener una fuente de luz estable y bien definida, que pueda recrear el espectro AM1.5G (que es el espectro de luz que llega a la superficie de la Tierra emitido por el Sol) para excitar las muestras que se encuentren bajo análisis. Todas las restricciones y parámetros que determinan si una fuente de luz es adecuada o no para este proceso están definidos por la Comisión Electrotécnica Internacional bajo el estándar IEC 60904-9. Durante el desarrollo de esta tesis, debido a la necesidad de caracterizar dispositivos, se optó por crear una de estas fuentes de luz. Así nació SUNBOX, nuestro simulador solar. SUNBOX pertenece a la clase AAA según el estándar IEC, lo que significa que posee la mayor calidad posible como simulador solar. Está completamente basado en diodos emisores de luz y también es personalizable, con un espectro ajustable que puede cubrir desde 0.2 hasta 1.2 soles. Dispone de 14 longitudes de onda de emisión diferentes que también pueden ser ajustadas libremente, de forma que se pueden realizar análisis en longitudes de onda concretas, tales como azul, ultravioleta o infrarrojo. Es fácilmente distinguible de sus contrapartes comerciales disponibles en el mercado, ya que su chasis está realizado por impresión 3D, así que es muy ligero y de bajo coste. Debido a la protección de la propiedad intelectual bajo un modelo de utilidad y un registro software, solo una parte del diseño electrónico se explica en este documento, junto con todo el procedimiento de calibración que se llevó a cabo en términos de coincidencia espectral, homogeneidad y estabilidad temporal, que clasifican a SUNBOX como un simulador solar de clase AAA. Al final de esta sección, se muestran algunas de las caracterizaciones de dispositivos llevadas a cabo con SUNBOX, usando sus diferentes funcionalidades para obtener parámetros clave de distintos tipos de celdas solares. Los métodos de caracterización llevados a cabo, tales como el trazado de curvas tensión corriente o la espectroscopía de impedancias también se explican en el documento. Por último, en la tercera sección, se estudian otras técnicas para mejorar la eficiencia de los dispositivos, basadas en el tratamiento óptico de la luz (gestión de la luz o "light management"). Esta gestión de la luz se basa en la habilidad que tienen algunos materiales para interactuar con la luz que incide sobre ellos. Normalmente estos materiales necesitan estar en forma de nanopartículas, nanobarras o pequeñas redes de difracción. Usando varios softwares de simulación (COMSOL® y JCMSuite®) basados en el método de elementos finitos (FEM), se han obtenido varios resultados que remarcan la importancia de incluir nanoestructuras dentro de los dispositivos, incrementando la cantidad de corriente fotogenerada en un 40% en un dispositivo basado en silicio amorfo hidrogenado y en un 20.5% en un dispositivo basado en un tándem de perovskita y silicio monocristalino. Además, se han obtenido resultados preliminares que demuestran que estas nanoestructuras pueden ser también muy efectivas no solo en dispositivos receptores de luz, sino también en emisores. En este caso se aplicó una nanoestructura a un diodo emisor de luz ultravioleta profunda, que mejoró su eficiencia de extracción de luz de un 4.57% a alrededor de un 15%, triplicando la cantidad de luz emitida con el mismo consumo de potencia eléctrica. En resumen, la conclusión principal de este trabajo es que es posible incrementar la eficiencia de los dispositivos actuales de una forma sustancial, quedando aún mucho espacio para mejorar. Se ha demostrado que un incremento en la eficiencia puede obtenerse no solo usando materiales novedosos con mejores propiedades ópticas y eléctricas, sino también optimizando los dispositivos existentes actualmente usando técnicas de gestión de la luz a través de la inclusión de nanoestructuras en estos dispositivos. Respecto a la primera aproximación, relacionada con la ciencia de materiales, en este trabajo se ha fabricado un material novedoso usando una técnica de fabricación poco explorada en estas aplicaciones (co-evaporación), descubriendo las propiedades y posibles aplicaciones de este material. Respecto a la segunda aproximación, relacionada con la fotónica, se han creado diseños de nanoestructuras y se ha simulado su respuesta, descubriendo una mejora muy importante en la eficiencia de los tres dispositivos estudiados. ; The present work has been funded from the following projects: • Comunidad de Madrid through SINFOTON-CM Research Program (S2013/MIT-2790) and SINFOTON2-CM (S2018/NMT-4326) • Ministerio de Economia, Agencia Estatal de Investigación and European Union's FEDER through TEC2016-77242-C3-(1-R, 2-R and 3-R) AEI/FEDER, UE Projects. • European Research Council (ERC) via Consolidator Grant (724424-No-LIMIT) • Generalitat Valenciana via Prometeo Grant Q-Devices (Prometeo/2018/098) • European Commission via FET Open grant (862656-DROP-IT) Also, this project could not be possible with the financial support of the Ministerio de Educación y Formación Profesional through the following grants that I have received: • Doctoral Grant FPU research fellowship (FPU17/00612). • Research Stay Grant (EST18/00399) supporting my research stay at Jaume I University (Castellón, Spain) • Research Stay Grant (EST19/00073) supporting my research stay at Helmholtz Zentrum Berlin and Zuse Institute Berlin (Berlin, Germany). ; Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de Madrid ; Presidente: Javier Alda Serrano.- Secretario: Fernando B. Naranjo Vega.- Vocal: Sven Burger

Detection of electromagnetic signals for applications such as health, product quality monitoring or astronomy requires highly responsive and wavelength selective devices. Photomultiplication-type organic photodetectors have been shown to achieve high quantum efficiencies mainly in the visible range. Much less research has been focused on realizing near-infrared narrowband devices. Here, we demonstrate fully vacuum-processed narrow- and broadband photomultiplication-type organic photodetectors. Devices are based on enhanced hole injection leading to a maximum external quantum efficiency of almost 2000% at -10V for the broadband device. The photomultiplicative effect is also observed in the charge-transfer state absorption region. By making use of an optical cavity device architecture, we enhance the charge-transfer response and demonstrate a wavelength tunable narrowband photomultiplication-type organic photodetector with external quantum efficiencies superior to those of pin-devices. The presented concept can further improve the performance of photodetectors based on the absorption of charge-transfer states, which were so far limited by the low external quantum efficiency provided by these devices. Photomutiplication-type organic photodetectors (PM-OPDs) are attractive for various next-generation technologies due to their lower cost, higher sensitivity and technological utility. Here, the authors report vacuum-processed narrowband PM-OPDs with enhanced sub-bandgap external quantum efficiency. ; J.K. acknowledges the German Academic Exchange Service for the Ph.D. fellowship. J.B. acknowledges the DFG project VA 1035/5-1 (Photogen) and the Sächsische Aufbaubank through project no. 100325708 (InfraKart). E.B. thanks Roland Schulze (IPF) for performing the ellipsometry measurements. L.B. acknowledges the European Union's Horizon 2020 research and innovation program under Marie Skłodowska-Curie Grant Agreement number 722651 (SEPOMO). ; Peer review information Nature Communications thanks Qiuming Yu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

High‐performance solar‐blind photodetectors are widely studied due to their unique significance in military and industrial applications. Yet the rational molecular design for materials to possess strong absorption in solar‐blind region is rarely addressed. Here, an organic solar‐blind photodetector is reported by designing a novel asymmetric molecule integrated strong solar‐blind absorption with high charge transport property. Such alkyl substituted [1]benzothieno[3,2‐b][1]‐benzothiophene (BTBT) derivatives Cn‐BTBTN (n = 6, 8, and 10) can be easily assembled into 2D molecular crystals and perform high mobility up to 3.28 cm(2) V(−1)s(−1), which is two orders of magnitude higher than the non‐substituted core BTBTN. Cn‐BTBTNs also exhibit dramatically higher thermal stability than the symmetric alkyl substituted C8‐BTBT. Moreover, C10‐BTBTN films with the highest mobility and strongest solar‐blind absorption among the Cn‐BTBTNs are applied for solar‐blind photodetectors, which reveal record‐high photosensitivity and detectivity up to 1.60 × 10(7) and 7.70 × 10(14) Jones. Photodetector arrays and flexible devices are also successfully fabricated. The design strategy can provide guidelines for developing materials featuring high thermal stability and stimulating such materials in solar‐blind photodetector application.

Hybrid organic-inorganic self-powered photodetectors with three different configurations were fabricated and their optoelectronic performance was determined. Si is the inorganic active layer and the transparent conductor poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is the organic layer. The basic photodetector structure under study is Au/PEDOT:PSS/Si/Al. This device shows high responsivity under low irradiation levels, as well as a wideband response in the visible and near-infrared wavelength ranges. To improve the performance of this basic device, its structure was modified by the addition of a nanostructured porous silicon (PSi) layer on top of the Si substrate. The resulting Au/PEDOT:PSS/PSi/Si/Al devices have been found to show improved photoresponse under high irradiation levels together with narrowband spectral responsivity in the infrared region. To further improve the optoelectronic performance of the photodetectors, Si + PSi micro-arrays were used instead of single PSi layers, leading to devices with the structure Au/PEDOT:PSS/(Si + PSi micro-arrays)/Si/Al. These devices possess a much improved performance, showing a responsivity of 1172.87 mA W-1, a specific detectivity of 5.81 × 1013 Jones, and a fast response speed of 396/412 μs at 0 V bias under white-light illumination (100 μW). Furthermore, a broadband spectral responsivity was achieved, with a maximum value of 473 mA W-1 at 853 nm. This improved behavior is associated with the combined effect of an effective reduction of the reflectance due to the presence of PSi and an improvement of the electrical conduction given by the presence of heavily-doped Si regions ; This research was partially funded by the Universidad Autónoma de Madrid, FPI-UAM grant and by the Egyptian Ministry of Higher Education, Missions Section under Egyptian Joint Supervision Grant. This work was part of ATTRACT that has received funding from the European Union's Horizon 2020 Research and Innovation Programme

In this work, we experimentally studied the influence of photoexcitation energy influence on the charge transport in organic semiconductors. Organic semiconductors were small molecules like corannulene, perylene and pentacene derivatives, polymers such as polythiophene and benzothiophene derivatives, and graphene, along with combinations of these materials in heterojunctions or composites. The first part of this study is focused on the photoexcitation energy influence on the transient photoconductivity of non-crystalline curved π-conjugated corannulene layers. The enhanced photoconductivity, in the energy range where optical absorption is absent, is deduced from theoretical predictions of corannulene gas-phase excited state spectra. Theoretical analysis reveals a consistent contribution involving transitions to Super Atomic Molecular Orbitals (SAMOs), a unique set of diffuse orbitals typical of curved π-conjugated molecules. More, the photoconductivity of the curved corannulene was compared to the π-conjugated planar N,N′-1H,1H- perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN2), where the photoexcitation energy dependence of photocurrent closely follows the optical absorption spectrum. We next characterized charge transport in poly(3-hexylthiophene) (P3HT) layers deposited from solution. Our results indicate that time-of-flight (TOF) mobility depends on the photoexcitation energy. It is 0.4× 10 −3 cm 2 /Vs at 2.3 eV (530 nm) and doubles at 4.8 eV (260 nm). TOF mobility was compared to field-effect (FET) mobility of P3HT field-effect transistors (OFETs). The FET mobility was similar to the 2.3 eV excitation TOF mobility. In order to improve charge mobility, graphene nanoparticles were blended within a P3HT solution before the deposition. We found that the mobility significantly improves upon the addition of graphene nanoparticles of a weight ratio as low as 0.2 %. FET mobility increases with graphene concentration up to a value of 2.3× 10 −2 cm 2 /Vs at 3.2 %. The results demonstrate that phase segregation starts to influence charge transport at graphene concentration of 0.8 % and above. Hence, the graphene cannot form a bridged conduction channel between electrodes, which would cancel the semiconducting effect of the polymer composite. An alternative approach to enhance mobility is to optimize the molecular ordering of organic semiconductors. For that purpose, we studied an innovative nanomesh device. Free-standing nanomesh devices were used to form nanojunctions of N,N′- iiDioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) nanowires and crystalline bis(triisopropylsilylethinyl)pentacene (TIPS-PEN). We characterized the photocurrent response time of this novel nanomesh scaffold device. The photoresponse time depends on the photon energy. It is between 4.5 − 5.6 ns at 500 nm excitation wavelength and between 6.7 − 7.7 ns at 700 nm excitation wavelength. In addition, we found that thermal annealing reduces charge carrier trapping in crystalline nanowires. This confirms that the structural defects are crucial to obtaining high photon-to-charge conversion efficiency and subsequent transport from pn junction in heterostructured materials. Structural defects also influence the power conversion efficiency of organic heterostructured photovoltaics (OPVs). Anticipating that polymers with different backbone lengths produce different level of structural defects, we examined charge transport dependence on the molecular weight of poly[4,8-bis(5-(2- ethylhexyl)thiophen-2-yl)benzo[1,2-b ; 4,5-b']dithiophene-2,6-diyl-alt-(4-(2- ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl] (PTB7-Th) from 50 kDa to 300 kDa. We found p-type hopping transport in PTB7-Th, characterized by 0.1 – 3× 10 −2 cm 2 /Vs mobility, which increases with temperature and electric field. The polymer molecular weight exhibits a non-trivial influence on charge transport. FET mobility in the saturation regime increases with molecular weight. A similar trend is observed in TOF mobility and FET mobility in the linear regime, except for the 100kDa polymer, which manifests in the highest mobility due to reduced charge trapping. The lowest trapping at the dielectric interface of OFET is observed at 200 kDa. In addition, the 200 kDa polymer exhibits the lowest activation energy of the charge transport. Although the 100 kDa polymer indicates the highest mobility, OPVs using the 200 kDa polymer exhibit the best performance in terms of power conversion efficiency. ; V disertaciji so predstavljeni rezultati eksperimentalnih raziskav o vplivu energije fotonov na fotovzbujeni transport naboja v organskih polprevodnikih. Organski polprevodniki, ki smo jih preučevali so bili v obliki majhnih molekul (koranulen, perilen in pentacenski derivati), polimerov (derivati politiofena in benzotiofena), grafena, ter kombinacije teh materialov v heterostrukturah in kompozitih. Prvi del je osredotočen na študij vpliva energije fotonov na optično absorpcijo in časovno-odvisni tok fotovzbujenih nosilcev naboja v tankih plasteh koranulena. Struktura molekule koranulena je ukrivljena in zaradi π-konjugacije izkazuje prevodnost fotovzbujenih nosilcev naboja. V energijskem območju, kjer koranulen nima optične absorpcije, smo opazili povečano prevodnost fotovzbujenih nosilcev naboja. Ta pojav smo razložili s pomočjo teoretičnih izračunov optičnih ekcitacij v molekuli koranulena, ki se nahaja v plinasti fazi. Analiza meritev je pokazala, da k povečani prevodnosti prispevajo fotovzbujeni nosilci naboja, ki so zaradi ustrezne energije fotonov vzbujeni v t.i. super atomske molekulske orbitale (SAMO). Te orbitale so značilne za ukrivljene π-konjugirane molekule. V molekulah, ki niso ukrivljene, teoretični izračuni ne napovedujejo SAMO orbital. Posledično, kot smo tudi pokazali s študijo prevodnosti fotovzbujenih tokov v derivatu molekule perilena, energijska odvisnost prevodnosti fotovzbujenih nosilcev naboja dosledno sledi optični absorpciji. V nadaljevanju so prikazani rezultati študije transporta naboja v plasteh poli(3- heksiltiofena) (P3HT), ki so bili nanešeni iz raztopine na steklene podloge. Rezultati nakazujejo, da je gibljivost fotovzbujenih nosilcev, ki je izmerjena preko metode časa preleta (TOF), odvisna od energije absorbiranih fotonov. TOF gibljivost znaša 0,4 × 10 -3 cm 2 /Vs pri energiji fotonov 2,3 eV (530 nm) in se podvoji pri 4,8 eV (260 nm). TOF gibljivost smo primerjali z gibljivostjo nosilcev naboja izmerjeno v P3HT tranzistorjih na poljski pojav (FET). FET gibljivost je podobna TOF gibljivosti pri energiji fotonov 2,3 eV. Pokazali smo, da se gibljivost poveča z dodatkom grafenskih nanodelcev. Nanodelce grafena smo dodali v raztopino P3HT v različnih masnih razmerjih pred nanosom na stekleno podlogo. Pokazali smo, da se gibljivost bistveno poveča že pri masnem razmerju grafena 0,2%. Z višanjem koncentracije se gibljivost veča. Pri najvišji koncentraciji 3,2%, ki smo jo pripravili, doseže FET gibljivost vrednost 2,3 × 10 -2 cm 2 /Vs. Ugotovili smo, da pri koncentracijah nad 0,8% pride do ivzbiranja grafena v skupke, kar prepreči, da bi grafen tvoril prevodni most med elektrodama in s tem izničil polprevodne lastnosti polimerskega kompozita. Alternativni pristop za povečanje gibljivosti nosilcev naboja v organskih polprevodnikih je povezan z urejanjem molekul v molekulskih kristalih. S tem namenom smo uporabili inovativno večplastno nanostrukturo elektrod, ki temelji na nanomrežici. Prostostoječo nanomrežico smo uporabili za tvorbo nano-stikov med nanožicami N, N'-dioktil-3,4,9,10-perilendikarboksimida (PTCDI-C8) in kristali bis(triizopropilsililetinil)pentacena (TIPS-PEN). Preučevali smo odzivni čas toka fotovzbujenih nosilcev naboja. Ugotovili smo, da je odzivni čas odvisen od energije fotonov. Pri vzbujanju z valovno dolžino 500 nm znaša odzivni čas 4,5 - 5,6 ns, pri 700 nm pa 6,7 - 7,7 ns. Poleg tega smo pokazali, da s termičnim popuščanjem izboljšamo odzivni čas, kar je posledica višje urejenosti molekul v nanožicah. S tem smo pokazali, da so strukturni defekti ključni dejavnik za učinkovitost pretvorbe fotonov v naboj na stiku med dvema polprevodnikoma in nadaljni transport po organskem polprevodniku. Strukturni defekti vplivajo tudi na učinkovitost pretvorbe svetlobne energije v električno energijo v organskih heterostrukturnih fotovoltaikih (OPV). Polimeri z različnimi dolžinami osnovne verige se različno uredijo in s tem tvorijo različno stopnjo strukturnih defektov. To smo dognali s tem, ko smo preučili odvisnost transporta nabojev od molekulske mase v poli[4,8-bis(5-(2-etilheksil)tiofen-2- il)benzo[1,2-b,4,5-b']ditiopen-2,6-diil-alt-(4-(2-etilheksil)-3-fluorotieno[3,4-b]tiofen- 2-karboksilat-2-6-diil] (PTB7-Th). Molekulska masa PTB7-Th je znašala od 50 kDa do 300 kDa. Pokazali smo, da so vrzeli glavni nosilci naboja v PTB7-Th. Njihova gibljivost znaša 0,1 - 3 × 10 -2 cm 2 /Vs. Gibljivost narašča s temperaturo in z električnim poljem, kar je značilno za transport naboja s poskakovanjem. Molekulska masa polimera ima netrivialen vpliv na transport naboja. FET gibljivost v nasičenem režimu se povečuje z molekulsko maso. Podoben trend smo opaziti tudi pri meritvu TOF gibljivosti, razen pri polimeru velikosti 100 kDa. Pri tem polimeru smo opazili, da je gibljivost največja zaradi najnižje gostote pasti, ki lovijo nosilce naboja. Poleg tega polimer z velikostjo 200 kDa kaže najnižjo aktivacijsko energijo transporta nosilcev naboja. Čeprav ima polimer velikosti 100 kDa največjo gibljivost, OPV-ji z uporabo polimera velikosti 200 kDa kažejo najboljšo učinkovitost v smislu učinkovitosti pretvorbe moči.

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record ; Indirect absorption extended below the direct transition edge and increase in carrier lifetime derived from Rashba spin-orbit coupling may advance the optoelectronic applications of metal halide perovskites. Spin-orbit coupling in halide perovskites is due to the presence of heavy elements in their structure. However, when these materials lack an inversion symmetry, for example by the application of strain, spin-orbit coupling becomes odd in the electron's momentum giving rise to a splitting in the electronic energy bands. Here we report on the observation of a large Rashba splitting of 117 meV at room temperature through a facile compositional engineering approach in halide perovskite single crystals, as predicted by relativistic first-principles calculations. Partial substitution of organic cations by rubidium ions in single crystals induces significant indirect absorption and dual emission as a result of a large Rashba splitting. We measured significant magneto-photocurrent, magneto-electroluminescence and magneto-photoluminescence responses in perovskite single crystal devices and thin films. They originate from the significant spin-momentum locking that leads to different precession frequencies of their respective spins about the applied magnetic field. A hybrid perovskite single crystal photodetector achieved record figures of merit, including detectivity of more than 1.3×1018 Jones which represents a three orders of magnitude improvement compared to the to date record. These findings show that facile compositional engineering of perovskite single crystals holds great promise for further advancing the optoelectronic properties of existing materials. ; European Regional Development Fund (ERDF) ; European Union Horizon 2020 ; Ministero dell'Istruzione dell'Universitàe della Ricerca (MIUR) ; Università degli Studi di Perugia ; CNPq, Brazil