Improving the efficiency and stability of perovskite solar cells by TiO2 nanocolumn arrays

Abstract

Organic-inorganic hybrid perovskite solar cells have attracted much attention due to their high power conversion efficiency (＞23%) and low-cost fabrication. Directions to further improve these solar cells include strategies to enhance their stability and their efficiency by modifying either the perovskite absorber layer or the electron/hole transport layer. For example, the transparent electron transport layer (ETL) can be an important tuning knob influencing the charge extraction1, light harvesting2, and stability3 in these solar cells. In this work, a series of TiO2 nanocolumn photonic structures has been fabricated by glancing angle deposition with sputtering and subsequent thermal oxidation and we studied in detail the effects of these TiO2 nanocolumns on the performance and the stability of Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 perovskite solar cells. Compared to devices with planar TiO2 ETLs, we found that TiO2 nanocolumns can significantly enhance the power conversion efficiency of the Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 perovskite solar cells by 17 % and prolong their shelf life. By analysing the optical properties, solar cells characteristics, as well as transport/recombination properties by impedance spectroscopy, we observed light-trapping and reduced carrier recombination in solar cells associated with the use of TiO2 nanocolumn arrays. The possible origins contributing to enhanced efficiency and stability of Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 perovskite solar cells by TiO2 nanocolumn arrays will be discussed.