Interface Engineering of Perovskite Absorber Layers by Polystyrene for Efficient and Reliable Inverted Perovskite Solar Cells

Recent advancements of perovskite solar cells (PSCs) have demonstrated high efficiency up to >25% with decent operational stability. The photovoltaic performance and stability of perovskite solar cells are constrained by the unstable interface between the perovskite absorber layer and the charge-transporting layer, because the interfaces of perovskite films inevitably possess imperfect crystals lattices, which primarily causes non-radiative recombination of charge carriers. Thus, the suitable passivating agents at selective interface are of importance to prepare high-quality perovskite absorber layers with less defective antisites. In this work, we applied polystyrene as a passivating agent for the interfaces of perovskite films, in particular top interface to hole transport layer (HTL) and the buried interface of perovskite absorber layer to the electron transport layer (ETL). The molecular structure of styrene, which is hydrophobic in nature, decreases interface traps, and nonradiative recombination, leading to improvements in optical and morphological properties. This hydrophobic characteristic also contributes to enhanced humidity stability, making the perovskite solar cells more stable under moisture exposure. Through the effective passivation provided by polystyrene, we observed enhancements in both optical and morphological characteristics, which contribute to optimizing solar cell performance. The perovskite solar cells with polystyrene exhibited the best efficiencies (22.60% for the bottom passivation with polystyrene) compared to control device (21.22%). Additionally, perovskite solar cells with polystyrene maintained about 85% of their initial efficiency after 1300 hours of humidity storage. These findings demonstrate that the incorporation of polystyrene not only facilitates and increases efficiency but also contributes to the enhancement of the overall stability of the solar cells.