Suchergebnisse

Voltage losses in singlet material-based organic photovoltaic devices (OPVs) have been intensively studied, whereas, only a few investigations on triplet material-based OPVs (T-OPVs) are reported. To investigate the voltage loss in T-OPVs, two homoleptic iridium(iii) complexes based on extended pi-conjugated benzo[g]phthalazine ligands, Ir(Ftbpa)(3) and Ir(FOtbpa)(3), are synthesized as sole electron donors. T-OPVs are fabricated by mixing two donors with phenyl-C-71-butyric acid methyl ester (PC71BM) as an electron acceptor. Insertion of oxygen-bridges as flexible inert delta-spacers in Ir(FOtbpa)(3) has slightly elevated both the lowest unoccupied molecular orbital and the highest occupied molecular orbital levels compared to those of Ir(Ftbpa)(3), which results in a lower charge transfer (CT) state energy (E-CT) for Ir(FOtbpa)(3)-based devices. However, a higher V-oc (0.88 V) is observed for Ir(FOtbpa)(3)-based devices than those of Ir(Ftbpa)(3) (0.80 V). To understand the above result, the morphologies of the two blend films are studied, which excludes the influence of morphology. Furthermore, radiative and non-radiative recombination in two devices is quantitatively investigated, which suggests that a higher V-oc can be attributed to reduced radiative and non-radiative recombination loss for the Ir(FOtbpa)(3)-based devices. ; Funding Agencies|Swedish Foundation for International Cooperation in Research and Higher Education (STINT); Knut and Alice Wallenberg foundationKnut & Alice Wallenberg Foundation [2016.0059]; Swedish Government Research Area in Materials Science on Functional Materials at Linkoping University [200900971]; China Scholarship Council (CSC)China Scholarship Council; NSFC of ChinaNational Natural Science Foundation of China [51711530040, 51473086]; National Postdoctoral Program for Innovative Talents [BX20180159]

Organic photovoltaics with the properties of flexibility, portability, and printability are ideal candidates for low-power-consumption electronics such as the Internet of Things under indoor light conditions. In this work, an all solution-processed integrated photocapacitor (IPC) consisting of an organic photovoltaic module (OPVM) and an asymmetric super-capacitor (ASC) is demonstrated. The OPVM poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b ]dithiophene)-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl)benzo[1, 2-c:4,5-c ]dithiophene-4,8-dione)] (PBDB-T) : 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2 ,3 d ]-s-indaceno[1,2-b:5,6-b-]-dithiophene (ITIC) with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the top electrode delivers a high power conversion efficiency of 6.7% with a voltage of 4.3 V (1 Sun). The ASC based on PEDOT:PSS and Ti3C2Tx electrodes shows a wide operation window of 1.5 V in the aqueous electrolyte with a high energy density of 28.7 mu W h cm(-2). Consequently, the IPC achieves a high output voltage of 3 V and outstanding overall efficiency of 6.0% (45 000 lx), which shows excellent stability as the solar-charging power unit under room light (500 lx). Synergizing energy harvest and storage in a solution-processed robust, lightweight, low-cost organic IPC enables this solar-charging power unit wide potential applications in low-power-consumption portable electronics. ; Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [2017-04123]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [200900971]; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation [2016.0059]; China Scholarship Council (CSC)China Scholarship Council; Jiaxing Public Welfare Research Program [2019AY11007]

Organic photovoltaic cells (OPVs) have attracted broad attention and become a very energetic field after the emergence of nonfullerene acceptors. Long-lifetime triplet excitons are expected to be good candidates for efficiently harvesting a photocurrent. Parallel with the development of OPVs based on singlet materials (S-OPVs), the potential of triplet materials as photoactive layers has been explored. However, so far, OPVs employing triplet materials in a bulk heterojunction have not exhibited better performance than S-OPVs. Here, the recent progress of representative OPVs based on triplet materials (T-OPVs) is briefly summarized. Based on that, the performance limitations of T-OPVs are analyzed. The shortage of desired triplet materials with favorable optoelectronic properties for OPVs, the tradeoff between long lifetime and high binding energy of triplet excitons, as well as the low charge mobility in most triplet materials are crucial issues restraining the efficiencies of T-OPVs. To overcome these limitations, first, novel materials with desired optoelectronic properties are urgently demanded; second, systematic investigation on the contribution and dynamics of triplet excitons in T-OPVs is necessary; third, close multidisciplinary collaboration is required, as proved by the development of S-OPVs. ; Funding Agencies|Knut and Alice Wallenberg foundation [2016.0059]; STINT funds for the Joint China-Sweden Mobility programme; Swedish Government Research Area in Materials Science on Functional Materials at Linkoping University Faculty Grant SFO-Mat-LiU [200900971]; China Scholarship Council (CSC); NSFC of China [51711530040, 51473086, 51773207, 91633301]; MOST [2017YFA0204702, 2018YFA0208504]

In this work, a novel lamination method employing hydrogen-bond interaction to assemble a highly conductive free standing poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film as a common electrode is demonstrated in a solution processed metal-free foldable integrated photocapacitor (IPC) composed of a monolithic organic solar cell (OSC) and a capacitor. The highlights of the work are:(1) micrometer free standing PEDOT:PSS electrode is successfully laminated onto a relatively large area (1 cm(2)) OSCs; (2) a free standing capacitor based on the PEDOT:PSS electrode is achieved; (3) the IPC demonstrates an overall efficiency of 2% and an energy storage efficiency of 58%, which is comparable with those of IPCs based on metallic common electrodes; (4) the novel lamination method for PEDOT:PSS electrode enables free standing PEDOT:PSS broad applications in solution processed flexible organic electronics, especially tandem or/and integrated organic electronic devices. Furthermore, the IPC is foldable with excellent cycling stability (no decay after 100 recycles at 1 mA cm(-2)). These results indicate that free standing PEDOT:PSS film is a promising candidate as common electrodes for IPCs to break the restrictions of metal electrodes. The demonstrated lamination method will greatly extend the applications of PEDOT:PSS electrodes to large area flexible organic electronic devices. ; Funding Agencies|Vinnova Marie Curie incoming project [2016-04112]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [200900971]; China Scholarship Council (CSC)

Low energy loss and efficient charge separation under small driving forces are the prerequisites for realizing high power conversion efficiency (PCE) in organic photovoltaics (OPVs). Here, a new molecular design of nonfullerene acceptors (NFAs) is proposed to address above two issues simultaneously by introducing asymmetric terminals. Two NFAs, BTP-S1 and BTP-S2, are constructed by introducing halogenated indandione (A(1)) and 3-dicyanomethylene-1-indanone (A(2)) as two different conjugated terminals on the central fused core (D), wherein they share the same backbone as well-known NFA Y6, but at different terminals. Such asymmetric NFAs with A(1)-D-A(2) structure exhibit superior photovoltaic properties when blended with polymer donor PM6. Energy loss analysis reveals that asymmetric molecule BTP-S2 with six chlorine atoms attached at the terminals enables the corresponding devices to give an outstanding electroluminescence quantum efficiency of 2.3 x 10(-2)%, one order of magnitude higher than devices based on symmetric Y6 (4.4 x 10(-3)%), thus significantly lowering the nonradiative loss and energy loss of the corresponding devices. Besides, asymmetric BTP-S1 and BTP-S2 with multiple halogen atoms at the terminals exhibit fast hole transfer to the donor PM6. As a result, OPVs based on the PM6:BTP-S2 blend realize a PCE of 16.37%, higher than that (15.79%) of PM6:Y6-based OPVs. A further optimization of the ternary blend (PM6:Y6:BTP-S2) results in a best PCE of 17.43%, which is among the highest efficiencies for single-junction OPVs. This work provides an effective approach to simultaneously lower the energy loss and promote the charge separation of OPVs by molecular design strategy. ; Funding Agencies|National Key Research and Development Program of China [2019YFA0705900]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [21734008, 21875216, 51803178, 61721005]; China Postdoctoral Science FoundationChina Postdoctoral Science Foundation [2017M621907, 2019T120501]; S&T Innovation 2025 Major Special Programme of Ningbo [2018B10055]; Research Grant Council of Hong KongHong Kong Research Grants Council [N_CUHK418/17, 14303519, 4053304]; Swedish Government Strategic Research Area in Material Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [200900971]; Swedish Research CouncilSwedish Research Council [2017-04123]; China Scholarship Council (CSC)China Scholarship Council

A free-standing high-output power density polymeric thermoelectric (TE) device is realized based on a highly conductive (approximate to 2500 S cm(-1)) structure-ordered poly(3,4-ethylenedioxythiophene):polystyrene sulfonate film (denoted as FS-PEDOT:PSS) with a Seebeck coefficient of 20.6 mu V K-1, an in-plane thermal conductivity of 0.64 W m(-1) K-1, and a peak power factor of 107 mu W K-2 m(-1) at room temperature. Under a small temperature gradient of 29 K, the TE device demonstrates a maximum output power density of 99 +/- 18.7 mu W cm(-2), which is the highest value achieved in pristine PEDOT:PSS based TE devices. In addition, a fivefold output power is demonstrated by series connecting five devices into a flexible thermoelectric module. The simplicity of assembling the films into flexible thermoelectric modules, the low out-of-plane thermal conductivity of 0.27 W m(-1) K-1, and free-standing feature indicates the potential to integrate the FS-PEDOT:PSS TE modules with textiles to power wearable electronics by harvesting human bodys heat. In addition to the high power factor, the high thermal stability of the FS-PEDOT:PSS films up to 250 degrees C is confirmed by in situ temperature-dependent X-ray diffraction and grazing incident wide angle X-ray scattering, which makes the FS-PEDOT:PSS films promising candidates for thermoelectric applications. ; Funding Agencies|Vinnova Marie Curie incoming project [2016-04112]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [200900971]; Recruitment Program of Global Youth Experts; National Natural Science Foundation of China [21474035]; United States National Science Foundation [DMR-1262261]; Open Fund of the State Key Laboratory of Luminescent Materials and Devices [2016-skllmd-03]; European Research Council [ERC 307596]