A Sol–Gel Processed Spinel HTL Combined with an Amphiphilic Polymer Interlayer for Stable and Scalable Tin-perovskite Solar Modules

A new, readily accessible inorganic hole transporting material (HTM), Cu²⁺ doped SnCo₂O₄ (Cu-SCO), is developed for inverted tin-perovskite solar modules (TPSMs). To overcome the intrinsic defect of inorganic solid-state material Cu-SCO and potential interfacial incompatibility with TPsk, an amphiphilic neutral donor-acceptor copolymer (PTSN) is rationally designed as a surface/interface modification agent. TPSMs based on Cu²⁺ doped SnCo₂O₄ HTLs integrated with PTSN surface/interface modification achieved the highest conversion efficiency of 10.4%. In contrast, the conversion efficiencies of TPSMs based on Cu-SCO HTL without interface passivation or using conventional PEDOT:PSS HTL are 8.69% and 7.99%, respectively. A large-area, high-quality Cu-SCO film is fabricated using a simple and scalable sol–gel method, enabling favorable transparency and hole mobility. The amphiphilic PTSN comprises a hydrophobic iso-propyltriphenylamine (i-Pr-TPA) unit that contributes to hole transport, and a hydrophilic cyclopentadithiophene derivative bearing alkylamine side chains (CPDT-A), which assists hole extraction and transport to the Cu-SCO layer. The amine nitrogen and thiophene sulfur in PTSN can coordinate with metal ions in both TPsk and Cu-SCO, while the π-electrons from its aromatic backbone can further interact with Cu-SCO, as evidenced by IR and XPS spectroscopy. Functionally, PTSN serves as a co-HTL, interfacial cross-linker, and defect passivator for both the HTL and the perovskite absorber. Additional advantages of PTSN include its neutral character—eliminating ion migration issues—dense film formation due to the D–A copolymer structure, and strong substrate adhesion enabled by multiple anchoring groups. Moreover, its amphiphilic nature facilitates the formation of uniform, high-quality perovskite films via solution processing. This study highlights a promising strategy that combines the sol–gel process with a molecularly engineered interfacial layer, paving the way for utilizing a wide range of solution-processable inorganic HTLs in large-area tin-based perovskite photovoltaic devices with good efficiency and stability.