Bulk heterojunction formation with induced concentration gradient from a bilayer structure of P3HT:CdSe/ZnS quantum dots using inter-diffusion process for developing high efficiency solar cell

Abstract

Bulk heterojunction (BHJ) solar cells consisting of poly(3-hexylthiophene) (P3HT) as donor and cadmium selenide/zinc sulphide (CdSe/ZnS) core shell quantum dots (QDs) as acceptor have been developed. Starting from the bilayer of P3HT/QD structure a BHJ is induced using the process of thermal inter-diffusion. The absorption measurements on the bilayer structure show that the absorption coefficient increases and the absorption spectrum becomes broader in the annealed device. Also, the photoluminescence of the annealed device is found to decrease by an order of magnitude showing a significant transfer of electrons to the QDs. With this approach and under broadband white light with an irradiance of 8.19 mW/cm 2, we have been able to achieve a power conversion efficiency of 5.1% and fill factor 0.45 for this solar cell. © 2012 Elsevier B.V. All rights reserved.