Low Temperature UV Sintering of Tantalum Doped TiO2 Electron Transporting Layers for High-Performance Flexible Perovskite Solar Cells

Abstract

Organometal halide perovskite solar cells (PSCs) have attracted significant attention due to its high conversion efficiency and low cost. In particular, the optimized design of an efficient electron transport layers (ETLs) is important to achieve high efficiency in OHPSCs. ETLs allow transport of electrons and avoid the recombination of charges by blocking the hole transfer to the anode. Convention ETL of high-efficiency perovskite solar cells had been synthesized with metal oxides such as Al2O3, TiO2, SnO2, which requires a high-temperature sintering process for electron transport. In addition, these processes could occur the deep electronic trap defects such as oxygen vacancies at the grain boundaries of ETLs, that would lead to unacceptable recombination. In this thesis, I control over the oxygen vacancy of TiO2 1D nanocrystals by Tantalum (Ta) cation. In addition, I prepared highly compact horizontally assembled (HA) Ta-doped TiO2 (Ta:TiO2) ETLs via UV-assisted solution process. The horizontally assembled Ta-doped TiO2 thin films show improved transmittance and hole blocking property, compared to a conventional pristine Ta-doped TiO2 thin films prepared using a high-temperature sintering process. Furthermore, HA Ta:TiO2 ETLs based PSC show improved photovoltaic performances and less hysteresis, compared to the HA Pristine TiO2 ETLs. The best-performing PSCs based on HA 3 at% Ta:TiO2 ETLs exhibit excellent power conversion efficiencies of 20.5% on FTO glass and 17.74% on ITO/PET.