23.2% efficient low band gap perovskite solar cells with cyanogen management †

Managing iodine formation is crucial for realising efficient and stable perovskite photovoltaics. Poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS) is a widely adopted hole transport material, particularly for perovskite solar cells (PSCs). However, improving the performance and stability of PEDOT:PSS based perovskite optoelectronics remains a key challenge. We show that amine-containing organic cations de-dope PEDOT:PSS, causing performance loss, which is partially recovered with thiocyanate additives. However, this comes at the expense of device stability due to cyanogen formation from thiocyanate–iodine interaction which is accelerated in the presence of moisture. To mitigate this degradation pathway, we incorporate an iodine reductant in lead–tin PSCs. The resulting devices show an improved power conversion efficiency of 23.2% which is among the highest reported for lead–tin PSCs, and ∼66% enhancement in the TS80 lifetime under maximum power point tracking and ambient conditions. These findings offer insights for designing next-generation hole extraction materials for more efficient and stable PSCs.