Optoelectrical modeling of solar cells based on c-Si/a-Si:H nanowire array: focus on the electrical transport in between the nanowires

Abstract

By coupling optical and electrical modeling, we have investigated the photovoltaic performances of p-i-n radial nanowires array based on crystalline p-type silicon (c-Si) core/hydrogenated amorphous silicon (a-Si:H) shell. By varying either the doping concentration of the c-Si core, or back contact work function we can separate and highlight the contribution to the cell's performance of the nanowires themselves (the radial cell) from the interspace between the nanowires (the planar cell). We show that the build-in potential (V ) in the radial and planar cells strongly depends on the doping of c-Si core and the work function of the back contact respectively. Consequently, the solar cell's performance is degraded if either the doping concentration of the c-Si core, or/and the work function of the back contact is too low. By inserting a thin (p) a-Si:H layer between both core/absorber and back contact/absorber, the performance of the solar cell can be improved by partly fixing the V at both interfaces due to strong electrostatic screening effect. Depositing such a buffer layer playing the role of an electrostatic screen for charge carriers is a suggested way of enhancing the performance of solar cells based on radial p-i-n or n-i-p nanowire array.

Determination of Defect Densities in Thin (i) a‐Si:H Used as the Passivation Layer in a‐Si:H/c‐Si Heterojunction Solar Cells from Static Planar Conductance Measurements

“…The conductance values extracted from numerical modeling have also been plotted (black line) in Figure 2a. With input para-meters for the (i) a-Si:H layer commonly used for device-grade (i) a-Si:H bulk material (see Supporting Information and previous studies [28][29][30][31][32] ), i.e., with low defect density (N G ¼3 Â 10 15 cm À3 eV À1 ) and a characteristic valence band tail width E 0,v of 43 meV, we observe that the variation with (i) a-Si:H thickness of simulated G norm does not match that of the experimental results. The experimental decrease in conductance is much stronger than that reproduced from numerical calculations.…”