Fine-tuning device performances of small molecule solar cells via the more polarized DPP-attached donor units

• Published in: Physical chemistry chemical physics : PCCP Vol. 14; no. 41; pp. 14238 - 14242
• Main Authors: Huang, Jianhua, Jia, Hui, Li, Liangjie, Lu, Zhenhuan, Zhang, Wenqing, He, Weiwei, Jiang, Bo, Tang, Ailing, Tan, Zhan'ao, Zhan, Chuanlang, Li, Yongfang, Yao, Jiannian
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 07.11.2012
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solar cell; Five membered ring; Sulfur heterocycle; Packing; Efficiency; Film; Device; Replacement; Thiophene; Conversion
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c2cp42050c

Three solution-processable small molecules of DPPT, DPPSe and DPPTT were synthesized by Stille coupling through attaching donor units of thiophene (T), selenophene (Se) and thieno[3,2-b]thiophene (TT) to the diketopyrrolopyrrole (DPP) core, respectively. Replacement of the T donors with the more polarized Se units results in a balance between the a and b direction packing and an obvious increase of the power conversion efficiency (PCE) from 1.90% to 2.33% with the increase of the short-circuit current (I(sc)) from 5.59 to 5.81 mA cm(-2) and the open-circuit voltage (V(oc)) from 0.78 V to 0.86 under the small molecule/acceptor ratio of 3 : 1. However, introduction of the conjugation-enlarged TT groups (versus the T units) leads to a decrease of the PCE, down to 1.70%, with a significant decrease of the fill factor (FF) (38% versus 44%), due to its poor film-forming characteristics.