2.1 Device characterization
The device structure used in the experiment is ITO/PEDOT:PSS/active
layer/PFN-Br/Al and the active layer is PBDB-TF:IT-4F. Figure
1 a shows the molecular formula of PBDB-TF and IT-4F. As shown in Figure
1b, the SEM cross-sectional picture presents the thickness of each layer
of the device. The favorable continuity of each layer reduces the
leakage current in the device, which is necessary for the regular
operation of the device. Figure S1a shows the J-V curve of the solar
cell. The corresponding IPCE spectrum and the integrated current
obtained by IPCE are given in Figure S1b. The short-circuit current
density (Jsc) of the cell is 20.12 mA/cm2, and the
obtained PCE can reach 13.12%.