19.36% Efficiency Organic Solar Cells Based on Low-Cost Terpolymer Donors with Simple Molecular Structures

Low cost and high performance are key elements for the industrialization of organic solar cells (OSCs). In view of this, developing highly-efficient organic photovoltaic molecules with simple chemical structure is one of the most effective countermeasures. Herein, three simple-structure terpolymers PTQ12-5, PTQ12-10, and PTQ12-15 are designed and synthesized, by embedding difluoro-substituted bithiophene (2T-2F) unit into the backbone of low-cost and high-efficiency polymer PTQ10. The synthesis of three terpolymers contains only two-step synthetic routes and over 85% synthetic yields from cheap raw compounds, thus exhibiting distinctly low-cost characteristic. Remarkably, PTQ12-5 shows significantly higher absorbance coefficient and hole mobility than PTQ10. Consequently, PTQ12-5-based OSCs shows more efficient exciton dissociation and charge transfer, suppressed carrier recombination, tighter molecular pi-pi stacking, and faster and more balanced charge transport, thus demonstrates a significantly improved efficiency of 18.77% than that of PTQ10-based device (18.03%). Moreover, an outstanding efficiency of 19.36% is achieved in PTQ12-5-based ternary device by further modulating the energy level alignment and blending features of photoactive molecules, which is the highest efficiency of OSCs based on low-cost polymers to date. This work has significant implications for guiding the design of low-cost and high-performance organic photovoltaic materials. By embedding the 2T-2F unit into the molecular backbone of the classic low-cost and high-efficiency polymer PTQ10, three low-cost terpolymer donors with simple structures are synthesized. The PTQ12-5-based organic solar cells achieve the highest power conversion efficiency of 19.36%, benefitting from the more efficient charge dissociation and transport, suppressed charge carrier recombination, and better phase separation morphology, etc. image