Boosting the Conductivity of Water/alcohol Processable Cathode Interface Layer Via Ti3C2 Doping for Efficient Organic Solar Cells

Poly(9,9-bis(3'-(N,N-dimethyl)-Nethylammonium-propyl-2,7-fluorene)-alt-2,7- (9,9-dioctylfluorene)) dibromide (PFN-Br) has been widely used as an cathode interface layer (CIL) for efficient organic solar cells (OSCs) because of its straightforward solution processability, excellent electron extraction ability, as well as prominent compatibility with various OSCs systems. However, the relatively low conductivity of PFN-Br results in CIL thicknesses usually <10 nm prepared from PFN-Br, which is obviously not conducive to the roll-to-roll largescale production of OSCs. In this work, titanium carbide (Ti3C2) was doped into the conventional CIL-material PFN-Br to improve the conductivity of PFN-Br, increase the electron extraction of the active layer, as well as optimize the ohmic contact between the CIL and the electrode. As a result, the power conversion efficiency (PCE) was boosted from 14.56 % to 15.80 % for OSCs based on PTzBI-oF:PYF-T-o, from 15.49 % to 17.27 % for OSCs based on PM6:L8-BO and from 17.65 % to 19.12 % for OSCs based on D18:L8-BO. The application of Ti3C2 doping PFN-Br strategy is expected to bring new opportunities for improving the conductivity of high performance CIL, so as to boost the PCE and promote the commercialization of OSCs.