A high-performance solution-processed small molecule: alkylselenophene-substituted benzodithiophene organic solar cell

Abstract

A solution-processed alkylselenophene-substituted benzodithiophene (BDT) small molecule, namely, 3,3′-((4,8-bis(5-(2-ethylhexyl)selenophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(thiophene-5,2-diyl))bis(5-octyl-1-(thiophen-2-yl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione) (BDTSe-TTPD), with broad absorption and suitable energy levels was synthesized. The widely used solvents o-dichlorobenzene (o-DCB), chlorobenzene (CB) or chloroform (CF) were used as the spin-coating solvent, to fabricate efficient photovoltaic devices with BDTSe-TTPD as the donor material and PC₇₁BM as the acceptor. Devices made from a CF solution demonstrated better performance in terms of short-circuit current, fill factor and power conversion efficiency, as compared to the devices made from the o-DCB and CB solutions. Finally, by optimizing the thickness of the active layer, a power conversion efficiency of 4.37% was achieved on devices with an area of 0.09 cm², under 100 mW cm⁻² of simulated AM 1.5 irradiation.