PEROVSKITE SEMICONDUCTOR OPTOELECTRONIC DEVICES

Surface passivation of perovskite film for efficient solar cells

Nat. Photonics, 2019, doi: 10.1038/s41566-019-0398-2

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) swiftly increased from 3.8% to more than 20% during last 10 years, thanks to the advancement of perovskite film growth, device and interface engineering. However, solution-processed perovskites are usually polycrystalline, that is the photoactive films contain substantial structural disorders, such as grain boundaries, interfaces and crystallographic defects. These defects have detrimental impacts on the performance and stability of PSCs.

In this work, a surface passivation approach was invented and investigated by the research team led by Prof. Jingbi You from Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China, based on which a high open circuit voltage (V_oc) and a high PCE were realized. Prof. You’s team developed an organic halide salt, phenethylammonium iodide (PEAI), for post-treatment of mixed perovskites FA_1-xMA_xPbI₃ (FA:HC(NH₂)₂; MA:CH₃NH₃) to suppress the surface defects of perovskite polycrystalline films. Surprisingly, the mere organic salt PEAI instead of the previously believed PEA₂PbI₄ 2D perovskite was responsible for the significant surface passivation effect. They carefully controlled the conversion between PEAI to PEA₂PbI₄ in the actual devices and discovered the existence of an thin layer of PEAI on top of perovskite surface, instead of PEA₂PbI₄, is the key to increasing the V_oc to as high as 1.18 V, which is 94.4% of the Shockley-Queisser limit V_oc (1.25 V). As a result, a 23.32% certificated efficiency (the highest PCE of PSCs of the article that has been reported in so far) was obtained by adopting this low-temperature solution-processed planar structure. This method is obviously meaningful for manufacturing low-cost, efficient and highly flexible perovskite solar cells.

Yang (Michael) Yang (State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, China)

doi: 10.1088/1674-4926/40/4/040204