Interfacial stability of organic-based hole transport layers in perovskite photovoltaics for space-like thermal environments

Perovskite solar cells (PSCs) are highly attractive for space applications due to their high power-to-weight ratio, yet their reliability under extreme thermal environments remains unclear. Here we investigate interfacial stability in devices employing polymeric PTAA, self-assembled monolayer MeO-2PACz, and a sequential PTAA/MeO-2PACz bilayer. Devices were evaluated under space-relevant conditions, including vacuum, AM0 illumination and thermal cycling spanning −40 °C to 90 °C. While MoO-2PACz enables high efficiency through interfacial engineering, it exhibits severe degradation under thermal tress due to thermomechanical mismatch with the perovskite layer, leading to interfacial defects and phase instability. In contrast, PTAA provides improved thermal stability but lower efficiency. The bilayer structure achieves both high efficiency and enhanced durability, retaining 73% of its initial performance after thermal cycling. This improvement arises from the polymeric layer mitigating thermomechanical stress and suppressing δ-phase transitions. These results suggest efficient interfacial thermomechanical engineering and strategy to thermal durability in PSCs for harsh space environments. Donghwan Yun and colleagues report that thermal instability in perovskite solar cells is governed by interfacial thermomechanical mismatch. Their bilayer hole transport strategy improves both efficiency and durability under space-like thermal cycling.