Six-fold Screening unfolds optimized Rylene Diimides towards Organic Solar Cell: A DFT Perspective

Abstract

Harnessing the sunlight to electricity is the most sustainable form of alternative energy. Apart from commercial silicon solar cells, organic solar cells (OSCs) have great potential due to their flexibility, processability and cost. To improve device performance, broadband absorption, electrical mobility and charge separation are the key components for optimization. Although discrete efforts have been dedicated comprehending the role of different chemical structures on their power conversion efficiencies (PCE), a systematic screening of multiple structural factors on PCE has been non-existent. Herein, we have shortlisted rylene diimides as the model acceptors in OSCs and demonstrated the role of a) expanding the rylene core (pyromellitic to bisazulene); b) changing ring size (5-member and 6-member) and positions (2,3- vs 1,8/9) of the diimide; c) changing diimide sidechain from alkyl to aryl, and d) twisting core-planarity of the rylene (pyrene to corannulene) and the effect on their structural parameters, optical absorption spectra and electron mobilities. Moreover, the combined six-fold screening predicts the candidate with highest electron mobility in the series. Such comprehensive assessment of critical factors on OSC performance will pave the way for improved design of acceptor molecules for higher PCE.