Nano‐cones on micro‐pyramids: modulated surface textures for maximal spectral response and high‐efficiency solar cells

Abstract

Abstract The front‐side reflection represents a significant optical loss in solar cells. One way to minimize this optical loss is to nano‐texture the front surface. Although nano‐textured surfaces have shown a broad‐band anti‐reflective effect, their light scattering and surface passivation properties are found to be generally worse than those of standard micro‐textured surfaces. To overcome these setbacks in crystalline silicon solar cells, advanced texturing and passivation approaches are here presented. In the first approach, we propose a modulated surface texture by superimposing nano‐cones on micro‐pyramidal surface texture. This advanced texture applied at the front side of crystalline silicon wafers completely suppresses the reflection in a broad wavelength range from 300 nm up to 1000 nm and efficiently scatters light up to 1200 nm. In the second approach, we show a method to minimize recombination at nano‐textured surfaces by using defect‐removal etching followed by dry thermal oxidation. These two approaches are applied here in an interdigitated back‐contacted crystalline silicon solar cell and result in decoupling of the interplay between the mechanisms behind short‐circuit current density and open‐circuit voltage. The device exhibits a conversion efficiency equal to 19.8%, record external quantum efficiency (78%) at short wavelengths (300 nm), and electrical performance equal to the performance of the reference interdigitated back‐contacted device based on front‐side micro‐pyramids. Copyright © 2015 John Wiley & Sons, Ltd.