Device simulation of intermediate band solar cells: Effects of doping and concentration

We present a numerical study on the fundamental operation principle of an intermediate band solar cell (IBSC) by using the self-consistent drift-diffusion method; the effects of doping in the IB region and incident light concentration on the operation characteristics are investigated. We find that under light illumination the electrostatic potential profile of IBSC strongly and intricately depends on both the electron density in IB and the carrier generation/recombination rates through IB. Introduction of doping in the IB region produces larger short-circuit current than that of IBSCs without doping under low light concentrations. Under high light concentrations, on the other hand, the doping dependence of the short-circuit current diminishes due to the photofilling effects. Although recombination processes through IB degrade the open-circuit voltage and fill factor compared to single junction solar cells under low light concentrations, they are greatly improved under high light concentrations by the photofilling effects. As a result, IBSCs could exceed in efficiency the single junction solar cells. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759134]