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Enhancing the JSC of P3HT-Based OSCs via a Thiophene-Fused Aromatic Heterocycle as a “π-Bridge” for A−π–D−π–A-Type Acceptors
journal contribution
posted on 2019-07-11, 19:46 authored by Jiacheng Wang, Tengfei Li, Xiaoxiao Wang, Yiqun Xiao, Cheng Zhong, Jiayu Wang, Kuan Liu, Xinhui Lu, Xiaowei Zhan, Xingguo ChenPoly(3-hexylthiophene) (P3HT)-based
organic solar cells (OSCs) have been extensively studied due to unique
advantages of P3HT such as roll-to-roll and large-area printing fabrication,
but a poor short-circuit current density greatly limits the enhancement
of power conversion efficiency (PCE). Herein, via the thiophene-fused
aromatic heterocycle as a “π-bridge”, two “A−π–D−π–A”-type
acceptors have been designed and synthesized for P3HT-based OSCs.
The aromaticity of the fused thiophene ring has effectively stabilized
the quinoid population, thus strengthening the intramolecular charge
transfer and further improving the current density. Owing to the weaker
electron-withdrawing ability of the thiophene-fused benzotriazole unit in JC2 than the thiophene-fused benzothiadiazole unit in JC1, a blue-shifted absorption occurs for JC2 to show a
better complementarity with P3HT to improve the light-harvesting efficiency
and current density of the derived OSCs, and an uplifted lowest unoccupied
molecular orbital energy level is also achieved for JC2 to obtain higher voltages. Thus, the P3HT:JC2-based
device exhibits a PCE of 6.24% with a high JSC of 13.96 mA cm–2 and a VOC of 0.71 V, significantly exceeding those of the P3HT:JC1 device with a PCE of 2.80%, a JSC of 10.66 mA cm–2, and a VOC of 0.48 V. This indicates that the fusion of a thiophene
ring onto a benzotriazole unit is an effective strategy to balance
the VOC and JSC of P3HT-based OSCs to achieve excellent photovoltaic performances.