Donor-Acceptor-Donor-Type Cyclopenta[2,1-b;3,4-b’]Dithiophene Derivatives As a New Class of Hole Transporting Materials for Highly Efficient and Stable Perovskite Solar Cells

Abstract

Three new donor-acceptor-donor-type (D-A-D) hole-transporting materials (HTMs), YC-1–YC-3, based on 4-dicyanomethylene-4H-cyclopenta[2,1-b;3,4-b’]dithiophene (DiCN-CPDT) core structure endowed with two arylamino-based units as peripheral groups were designed, synthesized and applied in perovskite solar cells (PSCs). Hole mobility, steady-state photoluminescence, thin-film surface morphology on top of perovskite layer, and photovoltaic performances for the YC series were systematically investigated and compared with that of Spiro-OMeTAD. It was found that YC-1 exhibited more efficient hole transport and extraction characteristics at the perovskite/HTM interface. Meanwhile, the film of YC-1 showed a homogeneous and dense capping layer coverage on perovskite layer without any pinholes, leading to the improvement of the fill factor and open circuit voltage. PSC device based on YC-1 as HTM exhibited a high power conversion efficiency (PCE) of 18.03%, which is comparable to that of the device based on the benchmark Spiro-OMeTAD (18.14%),1 and also a better long-term stability, with 85% of the initial efficiency retained after 500 hours storage under the condition of 30% relative humidity, presumably due to the hydrophobic nature of the material. This work demonstrates that the dicyanomethylene-CPDT-based derivatives are promising HTMs for efficient and stable PSCs.Y. S. Lin, S. Y. Abate, K. W. Lai, C. W. Chu, Y. D. Lin, Y. T. Tao, & S. S Sun, ACS Appl. Mater. Interfaces, 2018, 10, 41439. Figure 1