Single junction Binary and ternary polymer solar cells-based D-A structured copolymer with low lying HOMO energy level and two nonfullerene acceptorsстатья
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Аннотация:A donor–acceptor (D–A) conjugated copolymer denoted as PIJDTB-BDD) consisting ofbenzodithiophenedione (BDD) as a strong acceptor and dithienobenzene (DTB) as a weak donor wasprepared, and its optical and electrochemical properties were analyzed. PIJDTB-BDD) exhibited a deeperhighest occupied molecular orbital and an optical bandgap of 1.74 eV. Polymer solar cells (PSCs) werefabricated through blending PIJDTB-BDD) with two non-fullerene acceptors, i.e., narrow bandgap Y6 andmedium bandgap DBTBT-IC. The power conversion efficiencies (PCEs) of the PSCs using the bulkheterojunction active layer based on PIJDTB-BDD):DBTBT-IC and PIJDTB-BDD):Y6 were 13.16% and 12.62%,respectively. The larger open circuit voltage of the DBTBT-IC based PSCs as compared with that of the Y6counterpart was due to the up-shifted LUMO energy level of DBTBT-IC, and the high short circuit currentfor the Y6 based PSCs may be associated with the extended absorption profile of Y6. Taking advantage ofthe high open circuit voltage and short circuit current of the devices based on DBTBT-IC and Y6, theternary PSCs were prepared by optimizing the weight ratios between two acceptors and maintaining aconstant amount of PIJDTB-BDD); the resulting ternary PSCs based on PIJDTB-BDD) : DBTBT-IC : Y6 (1.0:0.2 : 1.0) showed an improved PCE of 16.32%, which is greater than those for the binary PSCs. Theenrichment in the PCE of the ternary device may be concomitant with the effective exploitation of excitonsQ4 via energy transfer from DBTBT-IC to Y6 and increased the D/A interfacial for more effective chargetransfer. The open circuit voltage of the PSC based on ternary lies in between that for the Y6 and DBTBTIC-based PSCs, demonstrating the formation of an alloy for the two acceptors.
