Balanced Charge Transport Optimizes Industry-Relevant Ternary Polymer Solar Cells

Bulk heterojunction polymer solar cells based on a novel combination of materials are fabricated using industry-compliant conditions for large area manufacturing. The relatively low-cost polymer PTQ10 is paired with the nonfullerene acceptor 4TIC-4F. Devices are processed using a nonhalogenated solvent to comply with industrial usage in absence of any thermal treatment to minimize the energy footprint of the fabrication. No solvent additive is used. Adding the well-known and low-cost fullerene derivative PC61BM acceptor to this binary blend to form a ternary blend, the power conversion efficiency (PCE) is improved from 8.4% to 9.9% due to increased fill factor (FF) and open-circuit voltage (V-OC) while simultaneously improving the stability. The introduction of PC61BM is able to balance the hole-electron mobility in the ternary blends, which is favourable for high FF. This charge transport behavior is correlated with the bulk heterojunction (BHJ) morphology deduced from grazing-incidence wide-angle X-ray scattering (GIWAXS), atomic force microscopy (AFM), and surface energy analysis. In addition, the industrial figure of merit (i-FOM) of this ternary blend is found to increase drastically upon addition of PC61BM due to an increased performance-stability-cost balance.