Field‐Induced Radial Junction for Dopant‐Free Crystalline Silicon Microwire Solar Cells with an Efficiency of Over 20%

Abstract

Radial junctions on crystalline silicon (c-Si) microwire structures considerably reduce the diffusion length of photoinduced minority carriers required for energy generation by decoupling light absorption and carrier separation in orthogonal spatial directions. Hence, radial junctions mitigate the need for high-purity materials, and thus reduce the fabrication cost of c-Si solar cells. In this study, the formation of dopant-free radial junctions from atomic layer deposition (ALD) of Al2O3 on an n-c-Si microwire surface is reported. ALD-Al2O3 generates a p(+) inversion layer, which eventually forms the radial junction on the n-c-Si surface. The width of depletion region induced by the p(+) inversion layer is calculated from PC1D simulation as 900 nm. The fabricated dopant-free radial junction c-Si solar cells exhibit a power conversion efficiency of 20.1%, which is higher than those of previously reported microwire-based radial junction solar cells. Notably, internal quantum efficiencies of over 90% are obtained in the 300-980 nm wavelength region, thereby verifying the successful formation of radial junctions.