Synergistic Dual-Ligand Precursors for Humidity-Tolerant Amorphous Oxide Thin Films in Cu(In,Ga),(S,Se) ₂ Solar Cells

Solution-processed multicomponent metal oxides hold promise for scalable thin-film technologies, yet their precursor chemistry is highly vulnerable to ambient moisture and oxygen, leading to premature hydrolysis, porosity, and cracking. Here we present a dual-ligand precursor engineering strategy that integrates citric acid (CA) and poly(acrylic acid) (PAA) within a methanolic nitrate system using poly(vinyl acetate) (PVAc) as a binder. CA provides chemical stabilization against hydrolysis, and PAA moderates stress during drying, yielding dense and crack-free amorphous oxide films under 25–30% relative humidity. As a proof of concept, these stabilized oxides were converted into Cu(In,Ga)(S,Se) 2 (CIGSSe) absorbers, which reproduced the morphology, composition, and bandgap grading of low-humidity references, yielding devices with largely recovered efficiencies. By prioritizing intrinsic precursor stabilization over strict environmental control, this work establishes a robust and generalizable framework for moisture-tolerant fabrication of multicomponent oxide films with broad applicability beyond photovoltaics.