Linear conjugated tetramer as a surface-modified layer to increase perovskite solar cell performance and stability

The surface-modified layer is important for the performance and stability of perovskite solar cells, but the research on surface-modified materials is still lagging behind perovskite materials in the photovoltaic field. In this work, a linear conjugated tetramer, IDTT4PDI, was developed through Stille coupling with a high synthetic yield. IDTT4PDI showed excellent solubility, thermal stability, a suitable LUMO level (-4.08 eV), and high electron mobility, implying that it would be suitable for use as a surface-modified layer in inverted perovskite solar cells. Use IDTT4PDI as a surface-modified layer improved the interfacial contact between the perovskite layer and PCBM film, reduced the trap-assisted recombination, and enhanced the electron transport efficiency. As a result, the efficiency of over 20% is achieved by the IDTT4PDI-modified MAPbI3 perovskite inverted device, which is much higher than the control device (17%). This work opens up a new direction for the use of linear perylene diimide derivatives as efficient surface-modified materials for achieving high-efficiency perovskite solar cells.