Non-linear Integral Equations Ideal Solar Cells Analysis with One and Two Intermediate Bands

E G. Ladopoulos

Abstract

An innovative and groundbreaking theory is proposed by using intermediate bands within the energy gap of the semiconductor in order to increase the efficiency of solar cells. Consequently, photons with energy less than the band gap may contribute to the output device by using the intermediate band or bands, in order to jump to the conduction band. This problem is reduced to the solution of non-linear integral equations and for their evaluation a special numerical method is proposed. Generally, in solar cells low energy photons cannot excite electrons to the conduction band and then to the external circuit. On the other hand, intermediate bands get advantage of the lower energy photons by allowing the electrons to be promoted to levels in the usually forbidden energy gap. Thus, through the above multi-step approach, then the efficiency of the solar cell is increasing. In the present research it will be shown that the maximum efficiency of an ideal solar cell containing one and two intermediate bands will be 63% and 75%, respectively. Keywords: Solar cell, intermediate band, conduction band, semiconductor, efficiency of ideal solar cell, non-linear integral equations, valence band, photons, electrons