Potassium-Doped\nNickel Oxide as the Hole Transport\nLayer for Efficient and Stable Inverted Perovskite Solar Cells

Abstract

Organic/inorganic\nhybrid perovskites have received a great deal\nof attention in solar energy harvest due to their high absorbance\nin the visible range, long carrier diffusion length, and solution\nprocessability. It is extremely important to develop high-quality\nhole transport layer (HTL) to replace PEDOT:PSS for fabricating inverted\nperovskite solar cells (PSCs) with high power conversion efficiency\n(PCE) and device stability. Upon this consideration, we proposed potassium\n(K)-doped nickel oxide (NiO_<i>x</i>) compact\nlayer via the sol–gel process to improve the conductivity and\nto modify its work function. Inverted PSCs with the configuration\nof FTO/K:NiO_<i>x</i>/Cs_0.05FA_0.81­MA_0.14Pb­(I_0.85­Br_0.15)₃/TBABF₄+PCBM/TIPD/Ag were fabricated\nand evaluated. We found that the device based on 3% K-doped NiO_<i>x</i> showed the best performance with an optimized\nPCE of 17.05% and a high fill factor of 74%, and it retained about\n80% of initial PCE value after\n35 days storage. Our results provide a simple and effective approach\nto fabricate inverted PSCs with high efficiency and long-term stability\nfor future production.