Dibenzo[f,h]thieno[3,4-b] quinoxaline–fullerene heterojunction bilayer solar cells with complementary spectrum coverage

In the present article, potential of a bilayer organic solar cell has been investigated. We utilize newly synthesized small molecules, namely dibenzo[f,h]thieno[3,4-b]quinoxaline as electron donors for solar cells in heterojunction bilayer configuration. These small molecules with a narrow absorption band in the range 400–450 nm provide a complementary spectrum for the fullerene C70, thereby leading to an overall power conversion efficiency of 2.6±0.2% under 100 mW/cm2 incident radiation. Thermal annealing seems to impact the charge separation at the donor–acceptor interface, which eventually affects device performance. This work demonstrates that carefully optimized bilayer devices are comparable to the bulk heterojunction counterparts.