题目:High-performance Perovskite Opotoelectronic Devices Enabled by Additives
时 间: 2019年7月4日 15：00
地 点: 清水河研究院大楼304A
高峰，瑞典Linköping University副教授，欧洲研究理事会启动基金（ERC Starting Grant）获得者，瑞典瓦伦堡学者（Wallenberg Academy Fellow）。2004与2007毕业于南京大学物理学系，获学士、硕士学位，2011年在剑桥大学获得博士学位。目前课题组的主要研究方向有机及钙钛矿光电器件。发表论文100余篇，包括以通讯作者或第一作者发表在Nature, Nature Materials, Nature Energy, Nature Photonics, PRL, Nature Communications, Advanced Materials等杂志。
Optoelectronic devices based on metal halide perovskites have developed very quickly during the past ten years. One of the important strategies to boost the performance is the employment of additives. In this talk, I will give two examples where the additives significantly improve the stability of perovskite solar cells and enhance the efficiency of perovskite light-emitting diodes (LEDs).
For perovskite solar cells, ion migration in the perovskite active layer, especially under light illumination and heat, is arguably the most difficult aspect to mitigate. We incorporate ionic liquids into the perovskite film, and demonstrate both a notable increase in efficiency and remarkable enhancement in long-term stability. We observe ~ 5% degradation of encapsulated devices under continuous simulated full-spectrum sunlight for over 1,800 hours at an elevated temperature of ~ 70 to 75 ˚C and estimate a T80 lifetime (time to 80% of its peak performance) of ~ 5,200 hours.
For perovskite LEDs, a major efficiency limit is trap-mediated non-radiative losses. Defect passivation using organic molecules has been identified as an attractive approach to tackle this issue. However, implementation of this approach has been hindered by a lack of deep understanding of how the molecular structures affect the passivation effectiveness. We reveal synergistic effect of precursor stoichiometry and interfacial reactions for perovskite LEDs.2 We show that hydrogen bonds play a critical role in affecting the passivation. By weakening the hydrogen bonding between the passivating functional moieties and the organic cation featuring the perovskite, we significantly enhance the interaction with defects sites and minimize non-radiative recombination losses. Consequently, we achieve exceptionally high-performance near infrared perovskite LEDs with a high external quantum efficiency (EQE) of 21.6%. In addition, our passivated perovskite LEDs maintain a high EQE of 20.1% and a wall-plug efficiency of 11.0% at a high current density of 200 mA cm-2.