Effects of absorption spectra overlapping on structural design of intermediate band solar cells

The intermediate band solar cells (IBSCs) operate by an additional carrier generation path via intermediate band (IB) state. One of the key operating parameters for IBSCs is the relationship between the absorption coefficients, which strongly affects the maximum conversion efficiency. If the absorption coefficient spectrum overlapping between the valence band (VB) to conduction band(CB) and VB to IB transition exists, carrier generation rate of host material band gap (CB-VB transition rates) will be reduced. By using the self-consistent drift-diffusion method with the local balance equation for the intermediate band, we have studied the effect of overlapping by tuning the device structural parameter of IBSCs. We assume zero surface recombination velocity which means ideal window layers near both front and back contact and existence of absorption spectrum overlapping between IB-CB and CB-VB transitions. As a result, the effect of the overlapping can be tailored by selecting a thicker emitter layer.