Efficient perovskite solar cells enabled by carborane-based interfacial grain boundary passivation

Perovskite solar cells (PSCs) have garnered worldwide research attention due to their exceptional power conversion efficiency. However, in inverted perovskite solar cells, severe non-radiative recombination occurs at the perovskite/C₆₀ electron transport layer interface, with interfacial grain boundaries serving as the primary sites. Therefore, suppressing non-radiative recombination at these interfacial grain boundaries is key to further improving device performance. In this work, we introduce 1, 2-Diphenyl-ortho-carborane (C₁₄H₂₀B₁₀, CBH-Ph) as an interfacial layer. Unlike previously reported materials that exhibit a uniform distribution at the interface, this material preferentially localizes at grain boundaries, effectively suppressing interfacial non-radiative recombination while modulating energy level alignment, thereby facilitating electron extraction and blocking hole transport. Furthermore, the hydrophobicity of CBH-Ph could effectively block the entry of water and oxygen molecules, thereby enhancing the long-term operational stability. Consequently, inverted PSCs fabricated via a one-step process achieve a maximum power conversion efficiency (PCE) of 25.23%, and the encapsulated devices retain 90% of their initial efficiency after 2000 h of exposure to 60% relative humidity at 25 °C.