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Organic Solar Cells Based on Polymer Acceptor and Small Molecule Donor with High Open-Circuit Voltage

Abstract

Organic solar cells (OSCs) based on small molecule donor (SD) and polymer acceptor (PA) show low power conversion efficiency (PCE) due to the limited number of small molecule donor–polymer acceptor combinations. In this work, we employ a polymer acceptor based on double B←N bridged bipyridyl (BNBP) unit to develop SD/PA-type OSCs. With poly[(N,N'-bis(2-hexyldecyl)-diamine-bis(difluoro-borane)-2,2-bipyridine)-alt-(2,5-thiophene)] (P-BNBP-T) as the acceptor and 7,7'-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene-2,6-diyl)bis(6-fluoro-4-(5'-hexyl-[2,2'-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole) (p-DTS(FBTTh2)2) as the donor, the OSC device shows a high open-circuit voltage (VOC) of 1.08 V and PCE of 3.50%. The VOC is ca. 0.3 V higher than that of other OSCs based on p-DTS(FBTTh2)2 due to the larger offset between the HOMO energy level of p-DTS(FBTTh2)2 and the higher-lying LUMO energy level of P-BNBP-T. The PCE of p-DTS(FBTTh2)2/P-BNBP-T is higher than that of any other OSCs based on p-DTS(FBTTh2)2/polymer acceptor blend reported so far. These results indicate that the BNBP-based polymer acceptors are promising for high-performance SD/PA-type OSCs. While the as-cast p-DTS(FBTTh2)2/P-BNBP-T blend film exhibits low molecular packing order and large-size phase separation, processing with solvent additive 1,8-diiodoctane (DIO) leads to continuous networks with small crystalline grains of p-DTS(FBTTh2)2 in the blend film. The resulting OSC device exhibits the best photovoltaic performance because of the improved exciton dissociation efficiency and charge transport ability.

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Publication details

The article was received on 08 May 2017, accepted on 14 Jun 2017 and first published on 15 Jun 2017


Article type: Paper
DOI: 10.1039/C7TC01996C
Citation: J. Mater. Chem. C, 2017, Accepted Manuscript
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    Organic Solar Cells Based on Polymer Acceptor and Small Molecule Donor with High Open-Circuit Voltage

    Z. Zhang, Z. Ding, X. Long, C. Dou, J. Liu and L. Wang, J. Mater. Chem. C, 2017, Accepted Manuscript , DOI: 10.1039/C7TC01996C

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