Suchergebnisse

Although the rapid development of organic-inorganic metal halide perovskite solar cells has led to certified power conversion efficiencies of above 20%, their poor stability remains a major challenge, preventing their practical commercialization. In this paper, we investigate the intrinsic origin of the poor stability in perovskite solar cells by using a confocal fluorescence microscope. We find that the degradation of perovskite films starts from grain boundaries and gradually extend to the center of the grains. Firmly based on our findings, we further demonstrate that the device stability can be significantly enhanced by increasing the grain size of perovskite crystals. Our results have important implications to further enhance the stability of optoelectronic devices based on metal halide perovskites. Published by AIP Publishing. ; Funding Agencies|National Basic Research Program of China-Fundamental Studies of Perovskite Solar Cells [2015CB932200]; Natural Science Foundation of Jiangsu Province, China [BK20140952, BK20150043]; National Natural Science Foundation of China [11474164, 61405091, 61634001]; Joint Research Program between China and European Union [2016YFE0112000]; Synergetic Innovation Center for Organic Electronics and Information Displays; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant) [SFO-Mat-LiU 2009-00971]; Swedish Research Council (VR); European Commission Marie Sklodowska-Curie actions [691210]

Efficiency roll-off is a major issue for most types of light-emitting diodes (LEDs), and its origins remain controversial. Here we present investigations of the efficiency roll-off in perovskite LEDs based on two-dimensional layered perovskites. By simultaneously measuring electroluminescence and photoluminescence on a working device, supported by transient photoluminescence decay measurements, we conclude that the efficiency roll-off in perovskite LEDs is mainly due to luminescence quenching which is likely caused by non-radiative Auger recombination. This detrimental effect can be suppressed by increasing the width of quantum wells, which can be easily realized in the layered perovskites by tuning the ratio of large and small organic cations in the precursor solution. This approach leads to the realization of a perovskite LED with a record external quantum efficiency of 12.7%, and the efficiency remains to be high, at approximately 10%, under a high current density of 500 mA cm(-2). ; Funding Agencies|National Basic Research Program of China-Fundamental Studies of Perovskite Solar Cells [2015CB932200]; European Union [2016YFE0112000]; Major Research Plan of the National Natural Science Foundation of China [91733302]; Natural Science Foundation of Jiangsu Province, China [BK20150043]; National Natural Science Foundation of China [11474164, 61405091, 61634001]; National Science Fund for Distinguished Young Scholars [6172550]; Synergetic Innovation Center for Organic Electronics and Information Displays; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; Swedish Research Council (VR); European Commission [691210]

Black phase CsPbI3 is attractive for optoelectronic devices, while usually it has a high formation energy and requires an annealing temperature of above 300 degrees C. The formation energy can be significantly reduced by adding HI in the precursor. However, the resulting films are not suitable for light-emitting applications due to the high trap densities and low photoluminescence quantum efficiencies, and the low temperature formation mechanism is not well understood yet. Here, we demonstrate a general approach for deposition of gamma -CsPbI3 films at 100 degrees C with high photoluminescence quantum efficiencies by adding organic ammonium cations, and the resulting light-emitting diode exhibits an external quantum efficiency of 10.4% with suppressed efficiency roll-off. We reveal that the low-temperature crystallization process is due to the formation of low-dimensional intermediate states, and followed by interionic exchange. This work provides perspectives to tune phase transition pathway at low temperature for CsPbI3 device applications. Exploiting low-temperature formed black phase CsPbI3 for light-emitting applications remains a challenge. Here, the authors propose a method to enable the deposition of gamma -CsPbI3 films at 100C and demonstrate a light-emitting diode with an external quantum efficiency of 10.4% with suppressed efficiency roll-off. ; Funding Agencies|Major Research Plan of the National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [91733302]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [51703094, 61935017, 61974066]; Natural Science Foundation of Jiangsu Province, ChinaNatural Science Foundation of Jiangsu Province [BK20170991]; National Science Fund for Distinguished Young ScholarsNational Natural Science Foundation of China (NSFC)National Science Fund for Distinguished Young Scholars [61725502]; Major Program of Natural Science Research of Jiangsu Higher Education Institutions of China [18KJA510002]; National Key Research and Development Program of China [2018YFB0406704]; Natural Science Fund for Colleges and Universities in Jiangsu Province of China [17KJB150023]; ERC Starting GrantEuropean Research Council (ERC) [717026]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; Marie Skodowska-Curie [798861]; Linkoping University

Solution-processable perovskites show highly emissive and good charge transport, making them attractive for low-cost light-emitting diodes (LEDs) with high energy conversion efficiencies. Despite recent advances in device efficiency, the stability of perovskite LEDs is still a major obstacle. Here, we demonstrate stable and bright perovskite LEDs with high energy conversion efficiencies by optimizing formamidinium lead iodide films. Our LEDs show an energy conversion efficiency of 10.7%, and an external quantum efficiency of 14.2% without outcoupling enhancement through controlling the concentration of the precursor solutions. The device shows low efficiency droop, i.e. 8.3% energy conversion efficiency and 14.0% external quantum efficiency at a current density of 300 mA cm(-2), making the device more efficient than state-of-the-art organic and quantum-dot LEDs at high current densities. Furthermore, the half-lifetime of device with benzylamine treatment is 23.7 hr under a current density of 100 mA cm(-2), comparable to the lifetime of near-infrared organic LEDs. ; Funding Agencies|Joint Research Program between China and European Union [2016YFE0112000]; Major Research Plan of the National Natural Science Foundation of China [91733302]; National Basic Research Program of China-Fundamental Studies of Perovskite Solar Cells [2015CB932200]; Natural Science Foundation of Jiangsu Province, China [BK20150043, BK20150064, BK20180085]; National Key R&D Program of China [2016YFB0401600, 2017YFB0404500, 2018YFB0406704]; National Natural Science Foundation of China [11474164, 61875084, 61634001, 51522209, 91433204]; National Science Fund for Distinguished Young Scholars [61725502]; Major Program of Natural Science Research of Jiangsu Higher Education Institutions of China [18KJA510002]; Synergetic Innovation Center for Organic Electronics and Information Displays; Natural Science Foundation of Zhejiang Province, China [LY17A040008]