The mechanism between solar cell efficiency and geometry of truncated quantum dots: implications for practical application

Quantum dots (QDs) have demonstrated significant potential as key candidates for enhancing the efficiency of intermediate-band solar cells (IBSCs). In this work, we present a theoretical investigation of the impact of truncated conical QD structures on the performance of QD-IBSCs. The Schrödinger equation, solved under the effective mass approximation, provides insight into the electron transition energies between the intermediate and conduction bands and the spatial probability density distribution of carriers within the structure. Our simulation results show strong efficiency dependence on structural parameters, such as QD density, height-to-bottom ratio, and barrier width. Reducing QDs from 20 to 10 results in a 6.54% decrease in electron ground state energy with increasing barrier width and QD height. Further reduction from 10 to 1 QD leads to a minor decrease of 3.75% for barrier width, while an increase in QD height results in a significant reduction of energy up to 11.9%. The power conversion efficiency increases significantly with higher QD densities, reaching 38.9% for 20 QDs compared to 14.7% for a single QD. Similarly, the short-circuit current density varies from 37.7 to 34.4 mA/cm² as the QD height-to-bottom ratio increases. Furthermore, the achieved optimum conversion efficiency is 39.6% for ratio 1. Our findings suggest that optimal performance can be achieved through smaller barrier width, higher QD densities, and larger QD sizes, making truncated conical QDs a promising geometry for next-generation high-efficiency QD-IBSCs.