Effect of cubic and spherical quantum dot size and size dispersion on the performance of quantum dot solar cells

We investigated the effect of cubic and spherical quantum dot size and size dispersion (size non-uniformity) on the absorption coefficient of a quantum dot ensemble. The absorption spectra of the cubic and spherical quantum dots (QDs) ensemble are found to be strongly dependent on the average size of QDs and the size distribution of QDs. Furthermore, we studied the effect of cubic and spherical quantum dot size and size dispersion on the QD photocurrent and efficiency of quantum dot solar cells (QDSCs). It is observed that there is an optimum size and size dispersion of QDs to achieve maximum QD photocurrent and efficiency. Embedding InAs QDs into the intrinsic region of a GaAs n-i-p solar cell improves performance from 20.3% to an ideal maximum of 34.4% (QDSC with cubic QD ensembles) and 36.5% (QDSC with spherical QD ensembles). The result shows that spherical morphology is better than cubic morphology. This theoretical study demonstrates that to achieve the highest possible power conversion efficiency, a suitable QD shape, optimized QD size, and size dispersion must be selected.