A Narrow-Bandgap n-Type Polymer with an Acceptor-Acceptor Backbone Enabling Efficient All-Polymer Solar Cells.
basic_science · Level V
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- Record sourced from PubMed, PMID 32954584.
- Also identified by DOI 10.1002/adma.202004183.
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Abstract
Narrow-bandgap polymer semiconductors are essential for advancing the development of organic solar cells. Here, a new narrow-bandgap polymer acceptor L14, featuring an acceptor-acceptor (A-A) type backbone, is synthesized by copolymerizing a dibrominated fused-ring electron acceptor (FREA) with distannylated bithiophene imide. Combining the advantages of both the FREA and the A-A polymer, L14 not only shows a narrow bandgap and high absorption coefficient, but also low-lying frontier molecular orbital (FMO) levels. Such FMO levels yield improved electron transfer character, but unexpectedly, without sacrificing open-circuit voltage (V<sub>oc</sub> ), which is attributed to a small nonradiative recombination loss (E<sub>loss,nr</sub> ) of 0.22 eV. Benefiting from the improved photocurrent along with the high fill factor and V<sub>oc</sub> , an excellent efficiency of 14.3% is achieved, which is among the highest values for all-polymer solar cells (all-PSCs). The results demonstrate the superiority of narrow-bandgap A-A type polymers for improving all-PSC performance and pave a way toward developing high-performance polymer acceptors for all-PSCs.