Letter A new dithienosilole-based oligothiophene with methyldicyanovinyl groups for high performance solution-processed organic solar cells Yuriy N. Luponosov a,⇑,1 , Jie Min b,⇑,1 , Tayebeh Ameri b , Christoph J. Brabec b,c , Sergei A. Ponomarenko a,d a Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya st. 70, Moscow 117393, Russia b Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University Erlangen-Nuremberg, Martensstraße 7, 91058 Erlangen, Germany c Bavarian Center for Applied Energy Research (ZAE Bayern), Haberstraße 2a, 91058 Erlangen, Germany d Chemistry Department, Moscow State University, Leninskie Gory 1-3, Moscow 119991, Russia article info Article history: Received 11 August 2014 Received in revised form 5 September 2014 Accepted 5 September 2014 Available online 18 September 2014 Keywords: Oligothiophene Donor–acceptor oligomer Organic solar cell Small molecule Dicyanovinyl groups abstract A new linear dithienosilole-based oligothiophene end-capped with methyl and electron- withdrawing dicyanovinyl groups, DTS(Oct) 2 -(2T-DCV-Me) 2 , was prepared in good yield. This oligomer exhibited broad absorption spectra in bulk down to the near-IR region with the optical edge at 900 nm, resulting in an initially high power conversion efficiency of 5.44% in solution-processed organic solar cells using PC 71 BM as an acceptor. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Organic solar cell technology is a promising candidate for the solar energy conversion compared to its inorganic counterparts due to its low cost, light weight, and potential use in flexible devices [1]. Solution-processed bulk hetero- junction organic solar cells (BHJ OSCs) possess potential for commercialization because of their high internal quantum efficiency and possibility to use large-scale printing tech- niques [2]. Today the most efficient organic solar cells (OSCs) based on polymer donor (D) and fullerene deriva- tive acceptor (A) achieve power conversion efficiencies (PCEs) over 10% both in single and tandem solar cells [3]. However polymers suffer from difficult purifications, broad molecular weight distributions, and batch to batch varia- tions. In a parallel effort, OSCs based on small molecules have attracted extensive attention due to easy mass-scale production, well-defined molecular structures, definite molecular weights, easily controlled high purity and well photovoltaic performance reproducibility [4]. Valuable insight into the design of oligomers for organic photovoltaics was given by the work of Bauerle et al., who have introduced the A–D–A strategy and used oligothioph- ene fragments as donor units and dicyanovinyl (DCV) groups as terminal acceptor units [5]. Chen et al. signifi- cantly extended design of donor–acceptor oligomers and used dithienosilole [6] or benzodithiophene [7] as central donor blocks and alkyl cyanoacetate [6,8] or rhodanine as acceptor groups [9]. Bazan et al. introduced D1–A–D2–A–D1 http://dx.doi.org/10.1016/j.orgel.2014.09.006 1566-1199/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding authors. E-mail addresses: luponosov@ispm.ru (Y.N. Luponosov), Min.Jie@ww. uni-erlangen.de (J. Min). 1 Yu. N. Luponosov and J. Min contributed equally. Organic Electronics 15 (2014) 3800–3804 Contents lists available at ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel