Abstract
Optimal active layer morphology is a prerequisite for high-efficiency all-polymer solar cells (all-PSCs). Herein, we report that the vertical phase separation as well as microstructures of the polymer donor and acceptor can be finely optimized in layer-by-layer (LbL) processed all-PSCs. By using 1-chloronaphthalene as the solvent additive during the deposition of the polymer acceptor in the top layer and applying thermal annealing on the entire active layer, bulk-heterojunction like morphology with favorable vertical composition distribution, improved lamellar ordering of the polymer donor (PBDB-T), and the formation of polymer fibrils of the polymer acceptor (PYT) have been realized simultaneously. This favorable morphology led to greatly enhanced exciton splitting efficiency, reduced trap density, improved charge transport, and suppressed charge recombination loss. As a result, the LbL processed all-PSCs of PBDB-T/PYT afforded a power conversion efficiency (PCE) of 16.05%, which is one of the highest PCEs for binary all-PSCs. Moreover, a fill factor (FF) of 0.77 has been obtained, which is the highest value for all-PSCs based on polymerized small molecule acceptors up to date. This work demonstrates an effective strategy for morphology optimization of LbL processed all-PSCs, which will greatly contribute to efficiency breakthrough.
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Bulk-heterojunction like morphology with favorable vertical composition distribution, improved lamellar ordering of polymer donor, and the formation of fibrils of polymer acceptor have been obtained in layer-by-layer processed all-polymer solar cells (all-PSCs). A remarkable power conversion efficiency of 16.05% and a record-high fill factor of 0.77 have thus been achieved in all-PSCs based on polymerized small molecular acceptors.
•The polymer microstructures can be well regulated in layer-by-layer (LbL) processed all-polymer solar cells (all-PSCs).•Bulk-heterojunction like morphology with favorable vertical phase separation has been obtained in LbL processed all-PSCs.•A remarkable power conversion efficiency of 16.05% and a record-high fill factor of 0.77 have been achieved in all-PSCs.