Electron-deficient fused dithieno-benzothiadiazole-bridged polymer acceptors for high-efficiency all-polymer solar cells with low energy loss

초록

A pair of A1-A2-type polymer acceptors (PY-DTBT and PY-DT-BT) including acceptor backbones (A1) with fusedor unfused-electron-deficient linkers dithieno-benzothiadiazole (DTBT) or DT-BT (A2), and corresponding comparative polymer acceptor PY-IT are synthesized for all-PSCs, respectively. PY-DTBT and PY-DT-BT neat film exhibit slightly blue-shifted absorption but higher absorption coefficients, and slightly down-shifted energy levels compared to PY-IT. Moreover, PY-DTBT exhibits a more rigid backbone with tighter interchain packing compared to PY-IT and PY-DT-BT, thus achieving better electron-transport in neat films. The PM6/PY-DTBT films possess well-distributed fibril network morphology with suitable phase segregation and better face-on crystallization, which can promote charge generation and extraction, and better-balanced charge mobilities in corresponding all-PSCs. Consequently, the PM6/PY-DTBT LBL-processed all-PSCs produce a top-ranked PCE of 17.58 % with a small energy loss (Eloss) of 0.51 eV, which is obviously higher than that of PM6/PY-IT (16.84 %) and PM6/PY-DT-BT (13.24 %). Furthermore, the all-PSCs based on PM6/(PY-DTBT90 %:PY-IT10 %) achieved a champion PCE of 18.5 % with remarkable FF, which is the one of highest reported value for the electron-deficient linker-based PSMAs in all-PSCs. This work demonstrates that employing DTBT as electron-deficient fused-ring linkage paves the way to achieve excellent polymer acceptors for further improving the efficiency of all-PSCs with small Eloss simultaneously.

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