Changing the Surface Morphology of a Silicon Wafer to Improve the Efficiency of Solar Cells

In the presented work, the authors considered the issue of increasing the efficiency of solar cells based on single-crystal silicon. The authors see the solution to the problem in modifying the surface morphology of the rear side of the solar cell by creating a porous layer. In the work, a porous layer was created by electrochemical etching of a plate with a fixed current density of 40 mA/cm^2, and by changing the anodization time from 5 to 20 sec. in 5 sec increments for different samples. As a result, 4 samples of plates with a porous layer were obtained, the thickness of which was determined by the etching time and amounted to 20, 40, 60 and 80 mm, respectively. Measurement of the reflection coefficient of the plates with the deposited porous layer were measured in the range of light emission in the range of 300..1000 nm. The results obtained show that an increase in the thickness of the porous film leads to a decrease in the reflection coefficient by 25% for a plate with a porous layer thickness of 80 mm. This effect leads to a significant scattering of the reflected light from the rear surface of the plate and, consequently, to an increase in the length of the light path inside the plate. The evaluation of the increase in the efficiency of the SC operation was carried out by measuring the current-voltage characteristics and comparing with the current-voltage characteristics of the SC, the morphology of the back side of which was not changed. As a result, it was found that the creation of a porous layer leads to a slight change in the open-circuit voltage of the SC, by less than 10%, but at the same time it allows to increase the short-circuit current by more than 4 times. Thus, we can conclude that the modification of the surface morphology of a silicon wafer by creating a porous layer on it leads to an increase in the efficiency of solar energy conversion.