Application of combinative TiO2nanorods and nanoparticles layer as the electron transport film in highly efficient mixed halides perovskite solar cells

Abstract

In this research a combinative electron transport layer (ETL) composed of TiO2nanocrystals (NCs) and nanorods (NRs) were prepared and applied in perovskite solar cells (PSCs). TiO2NCs with dominant size of 20 nm were synthesized through a hydrothermal method. TiO2NRs were also grown through another hydrothermal process using P25 TiO2nanoparticles (NPs) as the precursors. The diameter and length of the TiO2NRs were measured about 80 nm and 1–2 μm, respectively. Different combinative pastes including TiO2NCs and NRs were prepared and applied in ETL component of the PSCs. The weight percent (wt%) of the included TiO2NRs in electron transport layer was altered in the range of 0–20%. A conventional structure of FTO/TiO2compact layer/TiO2NCs-NRs mesoporous layer/Perovskite/Spiro-OMeTAD/Au. was utilized for fabrication of PSCs in ambient condition. Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3mixed halides perovskite was also used due to its proper bandgap energy, crystalline quality and longtime stability. The effect of ETL composition i.e. the weight percent of the composing TiO2NRs on the photovoltaic (PV) performance of the cells was investigated. According to the results, the PSC with a combinative ETL including 10 wt% of the TiO2NRs demonstrated a Jsc = 22.95 mA/cm2, Voc = 1.055 V, FF = 0.71 and η = 17.2%. This energy conversion efficiency was increased about 20% compared to that of the PSC with nanocrystalline, NRs-free ETL. The reason was attributed to the optimized electron transport property of the ETL and crystalline quality of the over-grown perovskite layer.