Molecular design of cost-effective donor polymers with high visible transmission for eco-friendly and efficient semitransparent organic solar cells

[Display omitted] •New donor polymers for semitransparent (ST) organic solar cells have been designed.•12 low-cost D–π = A-based polymers with high visible transmission were developed.•Halogenation and quaterpolymer strategies were used for structural optimization.•Best polymer overcomes inverse relation of efficiency and visible transmission.•ST module can substitute the power source of a thermo-hygrometer under low-light. Photoactive layer materials that overcome the trade-off between power conversion efficiency (PCE) and average visible transmittance (AVT) are required to prepare successful high-performance semitransparent organic solar cells (ST-OSCs). Among 12 novel cost-effective D–π=A polymers with high visible light transmission, P(3IN = 0.3)(3IN2F = 0.5)(BDD = 0.2) achieved a PCE of 14.0% and high stability in an eco-friendly solvent-processed OSC with BTP-eC9. This blend film exhibited an AVT of 62.1% and a color rendering index of 95.0, demonstrating the high potential for ST-OSCs. The ternary OSC with PM6 greatly enhances the PCE to 17.3%. Binary and ternary ST-OSCs achieve light utilization efficiencies (LUEs) of 4.38% and 4.04%, respectively, demonstrating the potential of the D–π=A structure. Under a 3000 K light-emitting diode light at 958 lx low illuminance, PCEs of 12.4% and 15.7% are obtained for binary and ternary ST-OSCs, respectively, and the indoor LUEs (LUIEs) of ST-OSCs are greatly enhanced to 5.52% and 5.48%, respectively. Air-processed eco-friendly ternary ST-OSC module (4.7 cm2) achieves not only a PCE of 12.1% and LUIE of 3.90% under 958 lx, but also color coordinates of (0.290, 0.323) and an infrared radiation rejection rate of 87.5%, meeting the civil engineering specifications for windows. This ST-OSC module can be a substitute power source of the thermo-hygrometer in real time, even operate at 195 lx, which paved the way towards zero-energy indoor and outdoor electrical devices as well as windows for buildings and vehicles.