Modelling of the electron concentration in an intermediate band

Semiconductors possessing an intermediate band (IB) have been shown to have great potential for use in photovoltaic devices. In this work we investigate some aspects related to photon absorption via intermediate bands. The basis for the calculations is to assume steady-state and thereby stating that the number of electrons leaving the IB must equal the number of electrons entering it. The electron density in the intermediate band is then calculated for different cases. It is shown that under illumination the IB will, in general, not be half-filled and the filling will vary spatially. The absorption coefficients for transitions involving the IB depend on the concentration of electrons in the IB and will thus vary with this concentration.