The Importance of End Groups for Solution‐Processed Small‐Molecule Bulk‐Heterojunction Photovoltaic Cells. Issue 9 (24th March 2016)

• Record Type: Journal Article
• Authors: Duan, Ruomeng; Cui, Yong; Zhao, Yanfei; Li, Chen; Chen, Long; Hou, Jianhui; Wagner, Manfred; Baumgarten, Martin; He, Chang; Müllen, Klaus
• Is Part Of: ChemSusChem. Volume 9:Issue 9(2016:May)
• Page Start: 973
• Page End: 980
• Publication Date: 2016-03-24
• Subjects: benzodithiophene -- bulk heterojunction -- small molecule -- solar cells -- thienothiophene; Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.201501626
• Languages: English
• ISSNs: 1864-5631

Abstract

Abstract: End groups in small‐molecule photovoltaic materials are important owing to their strong influence on molecular stability, solubility, energy levels, and aggregation behaviors. In this work, a series of donor–acceptor pentads (D2 –A–D1 –A–D2 ) were designed and synthesized, aiming to investigate the effect of the end groups on the materials properties and photovoltaic device performance. These molecules share identical central A–D1 –A triads (with benzodithiophene as D1 and 6‐carbonyl‐thieno[3, 4‐ b ]thiophene as A), but with various D2 end groups composed of alkyl‐substituted thiophene (T), thieno[3, 2‐ b ]thiophene (TT), and 2, 2′‐bithiophene (BT). The results indicate a relationship between conjugated segment/alkyl chain length of the end groups and the photovoltaic performance, which contributes to the evolving molecular design principles for high efficiency organic solar cells. Abstract : Finding the balance : Three novel donor–acceptor conjugated small molecule pentads (D2 –A–D1 –A–D2 ) are synthesized and applied in bulk‐heterojunction solar cells along with PC71 BM. By varying the conjugation length and alkyl substitution of the D2 end groups, the performance of the devices is optimized. The subtle demands of designing small molecules for OPV are highlighted, in which both the nature of the π system and the solubilizing side chains are critical.