Localized Potential Regulation on Polymer Donor Backbone Suppresses Energetic Disorder for Efficient, Stable and...

High energetic disorder and short exciton diffusion lengths in low-crystallinity polymer donors (P_Ds) critically limit exciton dissociation, charge transport, efficiency, stability, and scalability of organic solar cells (OSCs). Here we report a localized potential regulation strategy to intrinsically suppress energetic disorder of P_D through precise backbone engineering. By introducing a strongly electron-deficient unit into the structurally disordered backbone of the DP1, we developed a P_D DP10 that exhibits enhanced backbone rigidity, optimized local electronic polarization, and favorable miscibility with the acceptor L8-BO. These features synergistically reduce the exciton binding energy and suppress exciton-phonon coupling, thereby extending the exciton diffusion length from 15.5 to 19.9 nm. Consequently, DP10 enables balanced, trap-tolerant charge transport and reduced non-radiative recombination in devices. The DP10:L8-BO binary system achieves a device efficiency of 19.51%, together with exceptional thermal stability and outstanding thickness-tolerant performance. Additionally, a DP10:L8-BO:BTP-eC9 ternary device reaches an efficiency of 20.57% and a 15.1 cm² solar module delivers 17.20% efficiency, with impressive fill factors of 81.04% and 77.39%, respectively. This work establishes localized potential regulation as a powerful molecular design principle of P_Ds for simultaneously achieving high efficiency, thermal stability, and processing robustness in next-generation OSCs.