Increasing Quantum Dot Photovoltaic Cell By Fano Interference

In solar cells, the major loss comes from radiative recombination of carriers. Because of radiative recombination, there a part of electrons fall back to valance band from conductive band after they are promoted to conductive band. That is to say, this part of electrons cannot contribute to the cell’s current. Focusing on this case, Scully in2010publishes an article to show that the quantum coherence induced by external field can be used to enhance the solar cell’s efficiency. Later, Anatoly A. Svidzinsky et al. shows that the noise induced Fano coherence can also enhance the cell’s efficiency.In this article, we propose a5-level quantum dot solar cell (QDSC) model with a upper doublet level, a intermediate doublet level and a ground level. A photon with energy larger than the material band gap can be absorbed and promote a electron from valance band to conductive band directly. Besides, the photons with energy lower than the material band gap can also be absorbed and promote electrons from valance band to conductive band in a indirect manner. An electron can firstly jump from valance band to the intermediate band after absorbing a photon with small energy and then to the conductive band when absorbing another small energy photon. This lead to more use of the solar light spectrum. Benefited from the mature technique of modulation doping, the fabrication cost of intermediate solar cells is lower than the tandem solar cells, which make it more cost-effective.By building the system model of our5-level intermediate solar cell, we obtain the Hamiltonian of the system. Via the method of master equation, we present the dynamical evolution equations of level populations and solve these equations by numerical calculation. After express the cell’s current via level population, we present and analysis the functional relationship between the cell’s current and quantum coherence and have obtained the optimized coherence configuration to maximize the cell’s current. Compared to the current of no coherence, the current is significantly enhanced under optimized coherence configuration.