Thermal and Electrical Properties of ZnO-PCBM Composite Layer for p-i-n Perovskite Solar Cells

Expectations for commercialization of perovskite solar cells are increasing with the recent announcement of 25.8% efficiency. However, the stability of perovskite solar cells is still lower than that of silicon solar cells, which is an obstacle to commercialization. Solar cells driven in the field not only emit most of their energy as heat, but are also exposed to high temperatures of 80°C or more during operation, so thermal stability is very important. When the heat of the solar cell increases, not only the power conversion efficiency decreases, but also the stability of the perovskite(PVSK) materials becomes weak. In particular, since the p-i-n thin-film perovskite solar cells almost use an organic materials manufactured by a low-temperature process or a solution process, the thermal conductivity is very low. In general, phenyl-C61-butyric acid methyl ester(PCBM) is mainly used as electron transfer layer(ETL) of p-i-n structure, but its thermal conductivity is only 0.07W/mK preventing heat transfer inside the perovskite from escaping to the outside. In this study, the PCBM-ZnO composite layer was applied to improve the heat dissipation performance of the solar cell. The heat dissipation performance and electrical properties were investigated according to the amount of ZnO added between PCBM and perovskite layer. The addition of ZnO improved the thermal conductivity of ETL and improved the thermal stability of the PVSK layer. When the ZnO content was too high, ZnO was accumulated at the interface between PVSK and PCBM, reducing the solar cell efficiency. Therfore, it was confirmed that the ZnO content of 0.1 wt% was the optimal composition in this study. In conclusion, the improvement effect of the solar cell due to the application of the PCBM-ZnO composite layer was confirmed.