Enhancement of open circuit voltage in organic solar cells by doping a fluorescent red dye

Abstract

The open circuit voltage (V_OC) of small-molecule organic solar cells (OSCs) could be improved by doping suitable fluorescent dyes into the donor layers. In this paper, 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) was used as a dopant, and the performance of the OSCs with different DCJTB concentration in copper phthalocyanine (CuPc) was studied. The results showed that the V_OC of the OSC with 50% of DCJTB in CuPc increased by 15%, compared with that of the standard CuPc/fullerene (C₆₀) device. The enhancement of the V_OC was attributed to the lower highest occupied molecular orbital (HOMO) level in the DCJTB than that in the CuPc. Also, the light absorption intensity is enhanced between 400 and 550 nm, where CuPc and C₆₀ have low absorbance, leading to a broad absorption spectrum.

Keywords

organic solar cells (OSCs) / open circuit voltage / fluorescent dye doping / 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB)

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Acknowledgements

This work was partially supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 60736005 and 60425101-1), the Foundation for Innovative Research Groups of the NSFC (No. 60721001), the Provincial Program (No. 9140A02060609DZ0208), Doctoral Fund of Ministry of China (No. 20090185110020), the Hi-Tech Research and Development Program of China (No. 2007AA03Z424), the Project Sponsored by SRF for ROCS, SEM (No.GGRYJJ08-05), and Young Excellence Project of Sichuan (No.09ZQ026-074).

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