Effect of increasing etching time on the efficiency of porous silicon solar cells

Abstract

In this work, p-type silicon wafers were electrochemically etched to create nanocrystalline silicon (porous silicon (PS)) films. Different etching periods (5, 10, 15, and 20 minutes) were investigated to see how they affected the development of a nanosized pore array with a constant etching current density (10 mA/cm2). To prevent oxidation, PS samples were stored in methanol after preparation. PS is characterized by X-ray diffraction (XRD), and atomic force microscopy (AFM). At varied etching times (5, 10, 15, and 20 min), the crystallite size as determined by XRD was equal to (66.39, 88.13, 31.2, and 21.21) nm, respectively. The nanometric size was verified via AFM. The porosity of PS increased as the etching time increased; the maximum value was obtained at a 20-minute etching time. The C-V characteristic of PS/Si heterojunction describes control factors like built-in potential (Vbi) and the kind of connection, a linear relationship of 1/C2 with bias voltage indicating that the junction is an abrupt type. Vbi was calculated for PS/p-Si/Al heterojunction at different etching times, and it was between (1.1-1.8) volt. I-V characteristics under illumination showed an enhancement in the efficiency of the PS/Si/Al solar cells. The maximum value of the solar cell efficiency was 6.79% occurs at 15 min time of etching.