Optimizing High-Efficiency Multiple Exciton Generation-Enabled Quantum Dot Solar Cells

In this article, we have derived an expression for the generation rate to include critical multiple exciton generation (MEG) parameters, namely, MEGth and MEG efficiency, for a typical MEG-enabled quantum dot solar cell. Next, the characteristics of a three-layer quantum dot-sensitized solar cell (QDSSC) at varied MEG threshold, efficiency, and bandgap of the active layer have been examined by numerical analysis. The model used for analysis includes various physical phenomena at interfaces, inside transport layers, and in quantum dots (QDs), including quantum effects. Charge transport in QDs is considered to be governed by trap-assisted tunneling. It is found that we need a nanomaterial with such a property so that MEGth must be below
$3.5{E}_{\text {g}}$
and have a bandgap of around 0.94 eV to have enhanced power conversion efficiency (PCE) due to MEG at the device level. We further demonstrate that the PCE is limited by the reverse saturation current at lower bandgaps and effective solar flux at higher bandgaps beyond the maximum efficiency point. The proposed model can be employed to improve the device’s structure by using the computed value to foresee the QD’s size and composition since the QD’s bandgap energy directly relates to these two.