Enhanced Collection of Photocurrents Using Core–Shell Quantum Dots Decorated Polymer Composite Films

Abstract

Core−shell semiconductor quantum dots (SQDs) were synthesized via the microwave irradiation method from cadmium and zinc sulfides (Cd x S/ Zn 1−x S). The SQDs were incorporated into the electron transport layer of thin film polymer solar cells (TFPSCs) to assist in light trapping and charge collection processes. The up and down conversion of radiation in SQDs is expected to boost absorption between the lower energy bandgap core and wide energy bandgap shell, respectively. The investigation employs apolymers blend consisting of a poly [[4,8bis[(2-ethylhexyl) [3,4-b]thiophenediyl]]:[6,6]-phenyl C 71 butyric acid methyl ester (PTB7:PC71BM) as a photoactive medium of the solar cells. Consequently, the experimental evidence suggested that the inclusion of SQDs significantly improved the power conversion efficiency (PCE) of the solar cell as a result of increased energy transfer, exciton generation, and charge collection processes in TFPSCs. Furthermore, the performances of the solar cells are found to be dependent on the concentration of the SQD in the transport layer, where the highest PCE of 7.13% was measured at an optimal concentration of 0.375 wt %. This is an important development of the investigation with a recorded increment in PCE by nearly 23% from the reference cell.