Ganesh Datt Sharma
Organic solar cells (OSCs) consist of a bulk heterojunction (BHJ) active layer of carbon-based donor (D) and acceptor (A) materials, have many environmental advantages compared to other inorganic counterparts’ technologies. Moreover, OSCs can be manufactured through low cost printing technology on flexible substrates and have short pay-back time. In addition, OSCs can be made of different colors and semitransparent or transparent offering unique application, i.e. building integration and green houses. Early progress in OSCs are mainly based on fullerene derivatives (PC61BM or PC71BM) and achieved overall Power conversion efficiencies (PCEs) of around 11%, using either conjugated polymer or small molecule as donor component BHJ active layer [1]. However, fullerene derivatives suffer from several drawbacks, such as weak absorption in visible region of the solar spectrum, high synthesis costs, limited tailoring of energy levels and high voltage loss. As a consequence, it is not possible to improve the PCE of fullerene devices further. In an effort to overcome these obstacles, in the past two years a great deal of attention has been paid to the development of non-fullerene acceptors (NFAs), especially small molecule acceptors (SMA) [2]. After the limited time of research work on the designing of new SMA, the overall PCE of more than 16% [3-5] and 17 % [6] have been achieved for single junction and tandem based structures, respectively, and are on the road to the commercial reality