TiO2 composite electron transport layers for planar perovskite solar cells by mixed spray pyrolysis with precursor solution incorporating TiO2 nanoparticles**Project supported by the National Natural Science Foundation of China (Grant Nos. 51772125 and 51273079) and the Science Development Program of Jilin Province, China (Grant No. 20150519021JH).

Abstract

Perovskite solar cells with planar structure are attractive for their simplified device structure and reduced hysteresis effect. Compared to conventional mesoporous devices, TiO2 porous scaffold layers are removed in planar devices. Then, compact TiO2 electron transport layers take the functions of extracting electrons, transporting electrons, and blocking holes. Therefore, the properties of these compact TiO2 layers are important for the performance of solar cells. In this work, we develop a mixed spray pyrolysis method for producing compact TiO2 layers by incorporating TiO2 nanoparticles with different size into the precursor solutions. For the optimized nanoparticle size of 60 nm, a power conversion efficiency of 16.7% is achieved, which is obviously higher than that of devices without incorporated nanoparticles (9.9%). Further investigation reveals that the incorporation of nanoparticles can remarkably improve the charge extraction and recombination processes.