Six-fold screening unfolds optimized rylene diimides towards organic solar cells: a DFT perspective

Harnessing sunlight to produce 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 to comprehending the role of different chemical structures on their power conversion efficiencies (PCE), a systematic screening of multiple structural factors on PCE has not been reported. Herein, we shortlisted rylene diimides as model acceptors in OSCs and demonstrated the role of (a) expanding the rylene core (pyromellitic to bisazulene); (b) changing the ring size (five-member and six-member) and positions (2,3- vs. 1,8/9) of the diimide; (c) changing the diimide sidechain from alkyl to aryl; and (d) twisting core-planarity of rylene (pyrene to corannulene) and the effect on their structural parameters, optical absorption spectra and electron mobilities. Moreover, the combined six-fold screening predicted the candidate with the highest electron mobility in the series. This comprehensive assessment of critical factors on OSC performance paves the way for improved design of acceptor molecules for higher PCE.