Suchergebnisse

Bright and efficient blue emission is key to further development of metal halide perovskite light-emitting diodes. Although modifying bromide/chloride composition is straightforward to achieve blue emission, practical implementation of this strategy has been challenging due to poor colour stability and severe photoluminescence quenching. Both detrimental effects become increasingly prominent in perovskites with the high chloride content needed to produce blue emission. Here, we solve these critical challenges in mixed halide perovskites and demonstrate spectrally stable blue perovskite light-emitting diodes over a wide range of emission wavelengths from 490 to 451 nanometres. The emission colour is directly tuned by modifying the halide composition. Particularly, our blue and deep-blue light-emitting diodes based on three-dimensional perovskites show high EQE values of 11.0% and 5.5% with emission peaks at 477 and 467nm, respectively. These achievements are enabled by a vapour-assisted crystallization technique, which largely mitigates local compositional heterogeneity and ion migration. Achieving bright and efficient blue emission in metal halide perovskite light-emitting diodes has proven to be challenging. Here, the authors demonstrate high EQE and spectrally stable blue light-emitting diodes based on mixed halide perovskites, with emission from 490 to 451nm by using a vapour-assisted crystallization technique. ; Funding Agencies|ERC Starting GrantEuropean Research Council (ERC) [717026]; Swedish Energy Agency EnergimyndighetenSwedish Energy Agency [48758-1, 44651-1]; Swedish Research Council VRSwedish Research Council; NanoLund; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Bundesministerium fur Bildung und Forschung (BMBF Hyper project)Federal Ministry of Education & Research (BMBF) [03SF0514C]; DFG within the framework of SPP 2196 programmeGerman Research Foundation (DFG) [DE 830/22-1]; National Key Research and Development Program of China [2016YFB0700700]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [11704015, 51621003, 12074016]; Scientific Research Key Program of Beijing Municipal Commission of Education, China [KZ201310005002]; Beijing Innovation Team Building Program, China [IDHT20190503]

Multidentate molecular additives are widely used to passivate perovskite, yet the role of chelate effect is still unclear. Here, the authors investigate a wide range of additives with different coordination number and functional moieties to establish correlation between coordination affinity and perovskite crystallisation dynamics. Molecular additives are widely utilized to minimize non-radiative recombination in metal halide perovskite emitters due to their passivation effects from chemical bonds with ionic defects. However, a general and puzzling observation that can hardly be rationalized by passivation alone is that most of the molecular additives enabling high-efficiency perovskite light-emitting diodes (PeLEDs) are chelating (multidentate) molecules, while their respective monodentate counterparts receive limited attention. Here, we reveal the largely ignored yet critical role of the chelate effect on governing crystallization dynamics of perovskite emitters and mitigating trap-mediated non-radiative losses. Specifically, we discover that the chelate effect enhances lead-additive coordination affinity, enabling the formation of thermodynamically stable intermediate phases and inhibiting halide coordination-driven perovskite nucleation. The retarded perovskite nucleation and crystal growth are key to high crystal quality and thus efficient electroluminescence. Our work elucidates the full effects of molecular additives on PeLEDs by uncovering the chelate effect as an important feature within perovskite crystallization. As such, we open new prospects for the rationalized screening of highly effective molecular additives. ; Funding Agencies|ERC Starting GrantEuropean Research Council (ERC) [717026]; Swedish Energy Agency EnergimyndighetenSwedish Energy Agency [48758-1, 44651-1]; Swedish Research Council VRSwedish Research Council; NanoLund; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [91833303, 61974098, 62005126]; National Key Research and Development Program [2016YFA0201900]; Jiangsu High Educational Natural Science Foundation [18KJA430012]; 111 ProgramMinistry of Education, China - 111 Project; Collaborative Innovation Center of Suzhou Nano Science and Technology; Collaborative Innovation Center of Suzhou Nano Science Technology; Research Foundation - Flanders (FWO)FWO [12Y7218N, 12Y7221N, G098319N]; KU Leuven Research FundKU Leuven [C14/19/079, 201806920071, 201906830040, 201608530162, 201806460021]; China Scholarship CouncilChina Scholarship Council