Physics of the inter-subband transition in quantum-dot intermediate-band solar cell

This theoretical study sheds light on questions raised by inter-subband transition in quantum dot intermediate band solar cells. Based on a dedicated analytical model that correctly treats, from a quantum point-of-view, the trade-off between the absorption, the recombination and the electronic transport, we clearly show that it is essential to control the transit rate between the excited state of the quantum dot and the embedding semiconductor with a tunnel barrier. Such a barrier, matching the recombination and the tunnel rates, allows to strongly improve the current. On the other hand, by better controlling the retrapping, such a barrier can also improve the voltage. Finally this work, by giving a framework to design efficient inter-subband transitions, opens new opportunities for quantum dot intermediate-band solar cells.