Efficient inverted perovskite solar cells with truxene-bridged PDI trimers as electron transporting materials

Abstract

Two truxene-bridged PDI trimers were designed and synthesized as electron transporting materials (ETMs) in inverted perovskite solar cells (PSCs). The truxene moiety was chosen as the core structure, which was end-capped by perylene diimide (PDI) units through the C–C single bond (Tr-PDI₃) and the fused ring (Tr-PDI₃-C), respectively. It turned out that the perovskite active layer coated with Tr-PDI₃ exhibited smoother film morphology, and higher electron transport and extraction ability compared to that covered by Tr-PDI₃-C. As a result, a decent power conversion efficiency (PCE) of 17.45% was achieved in the Tr-PDI₃ based device, higher than that with the Tr-PDI₃-C electron transporting layer (16.90%). Notably, the performance of inverted PSCs was further enhanced by incorporating Tr-PDI₃ or Tr-PDI₃-C as the interfacial layer between the perovskite layer and the C₆₀ electron transporting layer. Champion PCEs of 19.83% and 19.24% were achieved in the devices based on the Tr-PDI₃ and Tr-PDI₃-C interlayer, respectively. The control device without an interlayer shows an inferior efficiency of 17.53%. These results demonstrate that Tr-PDI₃ and Tr-PDI₃-C are promising electron extraction and electron transporting materials in inverted PSCs.