Suppressing the blend morphology led intrinsic defects in organic photovoltaics towards undersea application

Due to the water absorption and reflection, the undersea solar spectrum blue-shifts with lower intensity and narrower width at larger depth. Though the organic solar cells (OSCs) are flexible to match the undersea solar spectrum and outperform the other photovoltaic techniques under weak light irradiation, the intrinsic defects from the bulk heterojunction (BHJ) morphology play a more negative role at this scene. The amorphous mixed donor:acceptor (D:A) blends make density of states (DOSs) overlap, which enlarges the energetic disorder by broadening the DOS distribution and produces more traps by extending the tail states. To alleviate these intrinsic defects, a two-step strategy including the production of larger componential phase separation and filling the tail-states by molecular doping is developed. The phase separation is enlarged by increasing the Flory-Huggins interaction parameter (χ) between the two photovoltaic components with polymethyl methacrylate (PMMA). The PMMA synergistically guides the subsequent molecular doping due to their pre-combination. Based on the above designs, the OSC's power conversion efficiency (PCE) improves from 18.0 % to 18.9 % under 1 Sun irradiation. More importantly, the values raise from 9.7 % to 10.7 % under the simulated light of 20 m depth in the South Pacific Ocean.