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

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.