Experimental and theoretical analysis of the optical behavior of textured silicon wafers

Optical analysis is performed for mono-crystalline silicon wafers with and without the texture and with and without the POCl doping, the passivating anti-reflective nitride film on front surface, and the screen printed aluminum conductor on the back surface. Reflectance is measured in the wavelength range from 300 nm to 1200 nm. Modeling of the light reflectance, absorbance, and transmittance is done using ray-tracing technique for the regular and the random texture patterns. Good agreement of measured and modeled data is obtained for the sub - 1 micron wavelengths by using standard material optical properties. However, the infrared light above the 1 micron wavelength requires accounting for several mono-layers thick native oxide present on silicon surfaces and adjusting the optical properties of specific nitride and aluminum films used in the solar cell manufacturing. It is found that the random texture exhibits 15% to 20% better light capture than the regular texture. Theoretical analysis provides plausible explanation of this effect and suggests a way to further improve optical performance of the textured surfaces. The optical modeling methodology can be used to find the optimum combination of texture and passivating/contact films for different solar cell designs.