Influence of Inorganic NiOx Hole Transport Layer on the Growth of CsBi3I10 Perovskite Films for Photovoltaic Applications

Lead (Pb)-free bismuth (Bi) halide perovskites are promising alternatives to Pb-based ones for the fabrication of perovskite solar cells (PSCs). However, the energy-level mismatch at the interface between Bi perovskite (CsBi3I10;CBI) and the charge carrier transport layer limits the performance of the PSCs. Here, spray pyrolysis processed nickel oxide (sp-NiOx) is reported as a hole transport layer (HTL) for CBI-based inverted planar PSCs. Influence of inorganic NiOx HTL is systematically studied on the structural and morphological properties of the CBI perovskite layer growth. The CBI perovskite deposited on top of the sp-NiOx exhibits improved crystallinity. The fabricated sp-NiOx layer also exhibits favorable optical and electrical properties. The deep valence band (-5.4 eV) of the sp-NiOx HTL is able to reduce the energy-level mismatch up to 0.3 eV at the interface with the CBI layer. The PSCs fabricated with sp-NiOx as HTL also exhibits a power conversion efficiency (PCE) of 0.72%, with a short-circuit current density of 2.89 mA cm(-2). The sp-NiOx HTL based device maintains 85% of its initial PCE value even after 100 h of light soaking. This work highlights the importance of having a suitable HTL along with appropriate interface engineering for the Bi halide photovoltaic devices.

Automated summary

In this study, spray pyrolysis processed nickel oxide was utilized as a hole transport layer for bismuth halide perovskite-based inverted planar perovskite solar cells. The use of nickel oxide HTL improved the crystallinity of the perovskite layer and reduced the energy-level mismatch at the interface between the perovskite and HTL. The PSCs fabricated with nickel oxide as HTL showed a power conversion efficiency of 0.72% and maintained 85% of its initial efficiency value even after 100 hours of light soaking.