Ideal Solar Cells Containing One and Two Intermediate Bands by Non-linear Integral Equations

Abstract

A new theory is proposed and investigated by using intermediate bands within the energy gap of the semiconductor in order to increase the efficiency of solar cells. Thus, the photons with energy less than the band gap could contribute to the output device by using the intermediate band or bands, in order to jump to the conduction band. Such a problem is reduced to the solution of non-linear integral equations and for their solution an innovative and groundbreaking numerical method is proposed. In general, in solar cells low energy photons can not excite electrons to the conduction band and then to the external circuit. Beyond the above, intermediate bands get advantage of the lower energy photons by allowing the electrons to be promoted to levels in the usually forbidden energy gap. Consequently, through such a multi-step approach, then the efficiency of the solar cell is increasing. In the current investigation will be shown that the maximum efficiency of an ideal solar cell containing one and two intermediate bands will be 63 % and 75 %, respectively.