Indolo[3,2-b]carbazole-based multi-donor–π–acceptor type organic dyes for highly efficient dye-sensitized solar cells

•Four novel indolo[3,2-b]carbazole-based organic dyes have been synthesized.•These dyes are designed as a multi-donor–π–acceptor type.•The secondary donors led to striking changes of the photoelectronic properties.•QX02 with diethylaniline as the secondary donor achieved a PCE of 8.09%.

Four novel indolo[3,2-b]carbazole-based multi-donor–π–acceptor type organic dyes QX01–04 have been designed, synthesized, and applied for dye-sensitized solar cells. These dyes consist of an indolo[3,2-b]carbazole core acting as the main donor group, a couple of groups such as ethylbenzene, N,N-diethylaniline, ethyloxylbenzene, and octyloxylbenzene acting as the secondary donors. The photophysical, electrochemical, and theoretical studies indicate that the four dyes are all capable as the photosensitizers. When introducing N,N-diethylaniline as the secondary donor, QX02 exhibits a broader absorption region and significantly improved IPCE values, which ensured a good light-harvesting ability and a high Jsc of 15.2 mA cm−2. Finally, QX02-based cell achieved a high efficiency of 8.09% which is very close to that of the commercial N719-based cell (8.26%) under 100 mW cm−2 irradiation.

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