Light harvesting enhancement upon incorporating alloy structured CdSeXTe1−X quantum dots in DPP:PC61BM bulk heterojunction solar cells

Abstract

Hybrid solar cells based on the pDPP5T-2 electron donating polymer, [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) and cadmium selenide telluride (CdSe_XTe_1−X) quantum dots (QDs) are fabricated and their photovoltaic performance and optoelectronic properties are investigated as a function of QD loading. The power conversion efficiency (PCE) of hybrid solar cells is improved up to 5.11% for the device containing 4 wt% of QDs which is mainly due to the enhancement in short circuit current density (J_sc) resulting from increased light harvesting. A full-fledged study is performed on the microstructure, charge transfer/transport and recombination mechanisms of our ternary hybrid solar cells by employing various advanced techniques. The transmission electron microscopy (TEM) results reveal the non-agglomerated and uniform distribution of the CdSe_XTe_1−X QDs within the pDPP5T-2:PC₆₁BM host matrix at low QD concentrations. Transient absorption spectroscopy (TAS) showed a slower charge carrier recombination rate due to the introduction of QDs into the photoactive layer. It can be attributed to the more efficient exciton dissociation in ternary systems. These findings are consistent with the photovoltaic properties of the device.