Developing The Performance of Double Quantum Dot Solar Cell Structure

Abstract

This work proposes a double quantum dot (QD) structure as an intermediate band for developing solar (SC) performance. The density matrix (DEMs) are written for this system, where coupled with the continuity-current equation and solved numerically to obtain the quantum efficiency (QE). Through this modeling, the momentum matrix elements of QD-QD, QD-wetting layer (WL), and WL-barrier transitions are calculated and the orthogonalized plane wave is assumed for WL-QD. This type of formulation is used for the first time and covers more characteristics than the rate equation modeling by addressing the interaction between all the states. Results are simulated both the excitonic and nonexcitonic (electron-hole( eh)) cases and show the importance of adding the QD layer.

For the eh model, the band-to-band recombination rates are high for least energy difference. The barrier and WL band-to-band recombinations rates are reduced by more than two orders compared to QD rates. The valence band relaxations are of the same order and higher than corresponding conduction band rates. The relaxations between respective states have higher rates than band-to-band rates.

The discrimination between states is increased under the excitonic model due to increasing hole occupation. The recombination rates are reduced with this model while the QD band-to-band recombination rates are increased. In both models, reducing the QD-QD recombinations and increasing all other recombinations increases the QE. The high QD band-to-band rate increases QE. Note that in the excitonic model, smaller rates than in eh model is enough for high QE.