Effect of electric field on carrier escape mechanisms in quantum dot intermediate band solar cells

Carrier escape and recombination from quantum dot (QD) states reduce the probability of two-step photon absorption (TSPA) by decreasing the available carrier population in the intermediate band (IB). In order to optimize the second photon absorption for future designs of quantum dot embedded intermediate band solar cells, the presented study combined the results of simulations and experiments to quantify the effect of electric field on the barrier height and the carrier escape from the QDs in InAs/GaAs quantum dot solar cells with five-layer QD superlattices. The electric field dependent effective barrier heights for ground state electrons were calculated using eight band k·p theory at short circuit conditions. With an increase in electric field surrounding the QDs from 5 kV/cm to 50 kV/cm, the effective barrier height of the ground state electrons was reduced from 147 meV to 136 meV, respectively. Thus, the increasing electric field not only exponentially enhances the ground state electron tunneling rate...