Ligand Engineering of Solution-Processed NiOx for High-Performance n-i-p Perovskite Photovoltaics

Abstract

In n-i-p halide perovskite solar cells (PSCs), replacing organic p-type semiconductors with inorganic alternatives offers significant potential for enhancing long-term stability. While nickel oxide (NiOx) gained prominence as a hole transport layer (HTL) in inverted architectures, traditional solution-deposition techniques for regular configurations face inherent limitations in reconciling colloidal stability, interfacial integrity, and charge transport efficiency. This study introduces a bifunctional ligand design strategy combining short- and long-chain molecules to engineer solution-processable NiOx nanoparticles into high-performance HTLs. The coordinated ligand system achieves three synergistic functions: (1) colloidal stabilization via synergistic adsorption energy modulation, (2) enhanced interparticle charge transfer through controlled C/Ni ratio reduction, and (3) interfacial energy alignment enabled by ligand-mediated charge redistribution. Additionally, incorporating 4.2 wt.% dopant-free poly(3-hexylthiophene) (P3HT) into the optimized NiOx matrix (termed NiPT-HTL) yields record power conversion efficiencies of 24.32% (0.09 cm2) for small-area devices and 22.34% (21.8 cm2) for minimodules, setting a new benchmark for NiOx-based n-i-p architectures. Moreover, the minimodules exhibit exceptional stability with <5% degradation after 700-hour damp-heat operation (60°C/50% RH). This work resolves the inherent incompatibility between solution processability and optoelectronic performance in metal oxide HTLs, establishing a materials innovation framework that bridges fundamental research with the scalable manufacturing of stable perovskite photovoltaics.