Opto-electro-thermal Multiphysical Mechanisms and Performance Degradation Mitigation in Perovskite/Silicon Tandem Solar Cells with Nonuniform Self-Assembled Monolayers

Perovskite/silicon tandem solar cells (PSTSCs) face a significant challenge in achieving uniform deposition of a self-assembled monolayer (SAM) on industrial-scale microtextured silicon substrates. In particular, nonuniform SAM coverage not only hinders the formation of high-quality perovskite films but also introduces additional interfacial defects and leads to further stress accumulation, thereby degrading device efficiency and stability. However, the underlying mechanisms behind nonuniform SAM coverage remain unclear. Here, we develop a comprehensive optoelectrothermal coupled simulation model to systematically investigate the optoelectronic coupling, carrier-ion dynamics, thermal-stress behavior, and corresponding mitigation strategies of nonuniform SAM-based PSTSCs. The simulation results reveal that nonuniform SAM coverage leads to inhomogeneous carrier transport and significantly increases carrier recombination in SAM-uncovered regions, particularly at the pyramid peaks, resulting in severe performance degradation. Additionally, nonuniform SAM coverage exhibits low tolerance to variations in perovskite film quality, interfacial passivation, reverse breakdown, and ion migration behavior. Moreover, residual stress induced by thermal mismatch shows a clear morphology dependence, with nonuniform SAM coverage leading to localized stress accumulation. Despite these adverse effects, we find that the performance degradation caused by nonuniform SAM coverage can be mitigated by increasing the photocurrent in the perovskite top cell, offering insights into designing high-efficiency and stable PSTSCs.