Science News: 2021 Adv. Energy Mater. Increased to PCE 23.91%! Introduce New 2D Layered Perovskites

　　Advanced Energy Materials (IF 29.368) published the research by Hyunjung Shin from Sungkyunkwan University in South Korea and others in September 2021. The most advanced perovskite solar cell has the disadvantage of insufficient charge extraction at the interfaces between light-absorbing perovskites and charge transport layers. In order to approach the Shockley-Quisse limit (Note: For any type of single-junction solar cell can reach the theoretical energy conversion limit), surface treatments and/or interface engineering are necessary. In this study, through a simple solution process, the authors introduced a new type of 2D layered perovskites, such as CHA₂PbI₄ (CHAI=cyclohexylammonium iodide) and CHMA₂PbI₄ ( CHMAI = cyclohexyl methyl ammonium iodide), between 3D perovskites and hole transporting layers, which in turn forms the 2D/3D heterojunction perovskite.

　　The charge extraction ability and recombination are directly measured by the transient photocurrent and photovoltage. Through its measurement, it is shown that the addition of 2D perovskites can promote efficient hole extraction with a favorable valence band alignment, and the self-luminescence emission quenching is observed. In addition, experiments with instruments such as solar simulators found that the interface resistance of the devices is significantly reduced by 30% compared with the devices without 2D perovskites. Due to the increase in open-circuit voltage (1.079 to 1.143V) and fill factor (78.22% to 84.25%), devices with 2D/3D perovskite heterojunction have improved power conversion efficiency (PCE) from 20.41% To 23.91%. The authors of this article provide detailed insights into hole extraction and high PCEs of 2D/3D perovskite heterojunction formation.