Cerium oxide standing out as an electron transport layer for efficient and stable perovskite solar cells processed at low temperature

Abstract

In high performance perovskite solar cells (PSCs), the electron transport layer (ETL) has overwhelmingly been dominated by compact titanium oxide (TiO₂), which typically requires sintering at around 500 °C. Such a high-temperature sintering procedure prevents TiO₂-based PSCs from matching well with plastic substrates and low-cost manufacturing. Here we report cerium oxide (CeO_x, x = 1.87), that was prepared facilely through a simple sol–gel method at low temperature (∼150 °C), as an alternative to high-temperature sintering processed TiO₂ in the regular architecture of PSCs. With a PCE of 14.32% from the involvement of an optimized CeO_x ETL through adjusting the precursor solution, and a higher PCE of 17.04% through introducing a [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) interfacial layer between the CeO_x ETL and the perovskite layer, the present work about CeO_x-based PSCs renders low-temperature solution-processed CeO_x an excellent ETL for high performance perovskite solar cells with improved stability.