Influence of thermal annealing-induced molecular aggregation on film properties and photovoltaic performance of bulk heterojunction solar cells based on a squaraine dye

Abstract

Squaraine (SQ) dyes have been considered as efficient photoactive materials for organic solar cells. In this work, we purposely controlled the molecular aggregation of an SQ dye, 2,4-bis[4-(N,N-dibutylamino)-2-dihydroxyphenyl] SQ (DBSQ-(OH)₂) in the DBSQ(OH)₂:[6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) blend film by using the thermal annealing method, to study the influence of the molecular aggregation on film properties as well as the photovoltaic performance of DBSQ(OH)₂:PCBM-based bulk heterojunction (BHJ) solar cells. Our results demonstrate that thermal annealing may change the aggregation behavior of DBSQ(OH)₂ in the DBSQ(OH)₂:PCBM film, and thus significantly influence the surface morphology, optical and electrical properties of the blend film, as well as the photovoltaic performance of DBSQ(OH)₂:PCBM BHJ cells.

Graphical abstract

Keywords

organic solar cells / squaraine dye / molecular aggregation / film properties / power conversion efficiency

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Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Grant No. 61604093), the Shanghai Pujiang Program (16PJ1403300), the Natural Science Foundation of Shanghai (16ZR1411000), the Science and Technology Commission of Shanghai Municipality Program (17DZ2281700), and the Shanghai Software and integrated circuit industry development special funds (170401).

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