Organic solar cells (OSCs) has driven their efficiencies to above 10 percent to reach a viable level for commercialization. However, the ...
Ultrafast Channel II process induced by a 3-D texture with enhanced acceptor order ranges for high-performance non-fullerene polymer solar cells
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Energy and Environmental Science, ISSN: 1754-5706, Vol: 11, Issue: 9, Page: 2569-2580
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- Environmental Science; Energy
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To achieve efficient non-fullerene polymer solar cells (NF-PSCs), an in-depth understanding of the key properties that govern the power output is necessary. Herein, three trialkylsilyl substituted benzodithiophene-based polymer donors (PJ1, PJ2, and PJ3) were synthesized with fine-tuning of the highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) and optical absorption. Using the polymer series paired with absorption-complementary small molecular acceptors (SMAs), namely, m-ITIC, IDIC, and AIDIC, we systematically studied the performance of a 3 × 3 matrix of NF-PSCs. An increasing open-circuit voltage with deepening HOMOs of the polymer donors, and the enhanced short-circuit current (J) and fill factor (FF) were ascribed to the well-intermixed blend morphology containing enhanced SMA order ranges with mixed face-on and edge-on orientations, the so-called 3-D texture. Such an optimal microstructure is best exemplified in the PJ2:IDIC combination, affording a highest efficiency of 12.01% with a simultaneously high J of 17.0 mA cm and FF of 75.3%. The devices with an active layer thickness of 300 nm still maintain an impressive efficiency approaching 10% with a decent FF of 60.0%. Moreover, the Channel II process, i.e., photoinduced hole transfer through acceptor excitation, was demonstrated to be crucially important for photocurrent generation. This study highlights the importance of optimizing the trade-off between charge separation/transport and domain size to achieve high-performance NF-PSCs.