Annealing-free sputtered NiO hole transport layers for large-area perovskite solar modules

Abstract

Nickel-oxide (NiO) is a widely adopted inorganic hole transport layer (HTL) for inverted (p-i-n) perovskite solar cells (PSCs). Its deposition by magnetron sputtering is particularly attractive for industrial deployment due to its uniformity, throughput, and large-area compatibility. Conventional sputtered NiOx typically requires post-deposition annealing (similar to 300( degrees)C) to achieve suitable HTL characteristics. Such annealing imposes severe constraints on large-area glass, flexible substrates, and tandem device stacks, and exacerbates reliability issues like alkali migration from soda-lime glass. Here, we demonstrate an annealing-free, large-area processed NiO, sputtered from a stoichiometric NiO target. Our process delivers HTL properties comparable to, or exceeding, those of conventionally annealed NiOx. Through a combined analysis of optical spectroscopy, ellipsometry, XPS/UPS, and transmission line measurements, we achieve high transparency, favorable energetics (Phi = 4.25 eV, reduced EF-EV), and tuneable p-type transport governed by controlled oxygen supply. Inverted PSCs employing such NiOx reach efficiencies of similar to 18% without any thermal treatment, matching annealed counterparts. With the inclusion of a self-assembled monolayer and passivation layers, the devices produce 22.5% efficiency. Crucially, we demonstrate process transfer to mini-(4 cm(2)) and large-area (781 cm(2)) modules, yielding comparable performance to annealed NiOx. Our mini-and large-area modules show efficiencies of 19.6% and 14.6% respectively.