Side chain modulated carbazole-based bifunctional hole-shuttle interlayer simultaneously improves interfacial energy level alignment and defect passivation in high-efficiency perovskite solar cells

Perovskite solar cells have reached a power conversion efficiency over 26.1 %, and the interface engineering between perovskite and hole transport layer (HTL) is crucial for achieving high performance. There exists a noticeable research gap when it comes to designing an interlayer layer that can both hold defect passivation and hole transportability. To bridge this gap, we have designed and synthesized two functional molecules with carbazole cores and side chain modifications, namely CVE-Br and CVE-DPA. Beyond the suitable energy levels of the carbazole group, CVE-Br can intercalate into perovskite lattice, create a low-dimensional perovskite, and further minimize defects. Instead of forming low dimensional structure, CVE-DPA molecule wraps around the perovskite. That makes it passivate perovskite defects and facilitate hole transport without the limitation of carrier transportation. As a result, the power conversion efficiency of perovskite solar cells with CVE-DPA can achieve 22.05 %. The hydrophobicity of CVE-DPA confers the corresponding devices to retain 87 % of the initial efficiency after 1000 h.