From nucleation control to voltage loss minimization: An asymmetric additive strategy for high-efficiency semitransparent organic solar cells

초록

The balance between power conversion efficiency (PCE) and average visible transmittance (AVT) remains a critical challenge for semitransparent organic solar cells (ST-OSCs). Narrow-bandgap systems, while promising for high transparency, typically suffer from excessive non-radiative energy losses Delta Vnr linked to low dielectric constants (epsilon(r)). Here, we report a solid additive engineering strategy employing a novel asymmetric molecule (named SZ) with distinct end-capping groups to simultaneously address energy loss and control film morphology. The pronounced structural asymmetry of SZ differentially templates the aggregation of the host acceptor Y6 in solution and functions as a more effective nucleating agent during film formation, thereby optimizing the molecular packing with tighter pi-pi stacking and enhanced crystallinity. Crucially, the strong dipole moment of SZ elevates the dielectric constant, which facilitates exciton dissociation and suppresses non-radiative recombination. Consequently, The PCE10-2F:Y6(SZ)-based opaque device achieves a significantly higher PCE of 14.35%, surpassing the 13.13% of the PCE10-2F:Y6-based devices, while Delta Vnr decreases from 0.301 eV to 0.280 eV. The ST-OSC based on PCE10-2F:Y6(SZ) achieves a breakthrough PCE of 11.00% with a high AVT of 44.8%. A champion light utilization efficiency (LUE) of 4.93% is achieved for ST-OSC, combined with excellent color neutrality and thermal insulation. This work demonstrates that asymmetry-driven additive design is a powerful approach to decouple the efficiency-transparency trade-off in multifunctional ST-OSCs.

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