Theoretical study of thin and thick emitter silicon solar cells

Abstract

We describe a complete theoretical model to calculate the open circuit voltage, the light generated current density, and the conversion efficiency of thin and thick emitter silicon solar cells. We show the importance of the Fermi carrier degeneracy, in addition to the heavy doping effects such as band-gap narrowing and Auger recombination. For example, in contradiction to recent calculations, the conversion efficiency of thin passivated emitter solar cells is shown to be independent of the surface dopant concentration. Also, in agreement with experimental results, but contrary to old conventional cell designs, it is shown that the conversion efficiencies of thick emitter solar cells can be as high as those of thin emitter cells. The last result will occur whenever the emitter is well passivated and the surface impurity concentration is relatively low (Ns=1×1019 cm−3). For non-passivated solar cells it is better to have thin emitters and high surface dopant concentrations (Ns≳2×1020 cm−3) as usual in conventional solar cells.