Radial junction Si micro/nano-wire array photovoltaics: Recent progress from theoretical investigation to experimental realization

Radial pn junction Si micro/nano-wire arrays exhibit unique optical and electrical characteristics for building photovoltaic devices with high performance-to-cost ratios over traditional planar junction bulk Si structures. Through optimizing the structural parameters, such as wire diameter and array periodicity, antireflection even superior to the optimized antireflective coatings can be realized. In the meantime, excellent light confinement is easily achievable for Si micro/nano-wire arrays using much less materials compared to their bulk Si counterparts. From the electrical aspect, the radial pn junction configuration formed around the wires significantly reduces the minority carrier collection length along the radial direction, providing outstanding tolerance to material qualities. Owing to these charming properties, radial junction Si micro/nano-wire array-based solar cells have been attracting extensive attention. The power conversion efficiency has also made huge progress from <1% to the present >12% in less than 10 years. With cell performance improvement, the number of research papers regarding theoretical understanding and optimization of the optical and electrical processes, experimental reports of the related solar cells has also surged, also including review papers. Accordingly, in this paper we are focusing on the recent progress, following a brief but systematic introduction to the related topic. Then the issues needing to be addressed for further improving the optical and electrical structures and cell performance are summarized. Following that, several other advanced solar cells employing Si micro/nano-wire arrays as a platform are introduced. (C) 2014 Elsevier Ltd. All rights reserved.