Insertion of a thin highly doped crystalline layer in silicon heterojunction solar cells: Simulation and perspectives towards a highly efficient cell concept

Abstract

An emerging cell concept based on silicon heterojunctions called hetero-homojunction is investigated by means of numerical simulations. Compared to the usual amorphous/crystalline silicon (a-Si:H/c-Si) heterojunction architecture, the hetero-homojunction cell contains an additional thin and highly doped (p+)- or (n+)- c-Si layer at the front or back (i)a-Si:H/(n)c-Si interface, respectively. In this paper, we show the dependence of solar cell performance on the additional heavily doped c-Si layer parameters (thickness and doping) and a-Si:H/c-Si interface properties. Insertion of the (p+)c-Si improves the cell power conversion efficiency by almost 1% absolute and lowers its sensitivity to a-Si:H/c-Si interface defects. Improved field effect passivation leading to higher open circuit voltage and fill factor is evidenced and the added layer is optimized with regard to hetero-homojunction cell efficiency. The (n+)c-Si layer addition also decreases the recombination rate at the back hetero-interface but does not improve significantly the conversion efficiency. The latter result is finally discussed.