Detrimental Effect of Excess PbI2 on the Stability of Perovskite Solar Cells
Ganbaatar Tumen-Ulzii a b, Chuanjiang Qin a b, Toshinori Matsushima a b c, Chihaya Adachi a b c
a OPERA, Kyushu University, Japan
b Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project
c International Institute for Carbon-Neutral Energy Research(I2CNER), Kyushu University
Oral, Ganbaatar Tumen-Ulzii, presentation 031
Publication date: 14th October 2019




Organic-inorganic lead halide perovskite solar cells (PSCs) are one of the most promising technologies for solar energy harvesting. The record power conversion efficiency (PCE) of PSCs has now reached 25.2%. Excess/unreacted lead iodide (PbI2) crystals are often seen in perovskite films, and are believed to increase PCEs of PSCs because of passivating the trap states. Nevertheless, how PbI2 crystals affect long-term stability of PSCs under continuous light irradiation has been rarely studied. Therefore, the clarification of basic degradation mechanisms related to unreacted PbI2 is important for improving the stability of PSCs. Here, we show that unreacted PbI2 crystals are one of the main reasons for degradation of PSCs. Under continuous illumination of light, unreacted PbI2 undergone the photo-decomposition by forming metallic Pb. Indeed, the degradation of PSCs was accelerated by metallic Pb. By carefully reducing the amount of the unreacted PbI2, the stability of PSCs is greatly improved; almost no degradation of PCEs was observed even after 500 hours of continuous illumination with maximum power point tracking.





This work was supported by the Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project (JST ERATO Grant Number JPMJER1305), by the International Institute for Carbon-Neutral Energy Research (WPI-I2CNER) sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, by JSPS KAKENHI (grant numbers JP15K14149 and JP16H04192), and by The Canon Foundation.


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