Investigation of post-thermal annealing-induced enhancement in photovoltaic performance for squaraine-based organic solar cells

Abstract

In this work, we have systematically investigated the post-thermal annealing-induced enhancement in photovoltaic performance of a 2,4-bis[4-(N, N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (DIBSQ)/C₆₀ planar heterojunction (PHJ) organic solar cells (OSCs). An increased power conversion efficiency (PCE) of 3.28% has been realized from a DIBSQ/C₆₀ device with thermal annealing at 100 °C for 4 min, which is about 33% enhancement compared with that of the as-cast device. The improvement of the device performance may be mainly ascribed to the crystallinity of the DIBSQ film with post-thermal annealing, which will change the DIBSQ donor and C₆₀ acceptor interface from PHJ to hybrid planar-mixed heterojunction. This new donor–acceptor heterojunction structure will significantly improve the charge separation and charge collection efficiency, as well as the open circuit voltage (V_oc) of the device, leading to an enhanced PCE. This work provides an effective strategy to improve the photovoltaic performance of SQ-based OSCs.

Keywords

organic solar cell / squaraine dye / post-thermal annealing / donor/acceptor interface / 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 Natural Science Foundation of Shanghai (Grant Nos. 16ZR1411000 and 18ZR1413800), and the Natural Science Foundation of Jiangsu Province of China (Grant No. BK20180978).

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