Micro/Nanostructures for Light Trapping in Monocrystalline Silicon Solar Cells

Abstract

Due to the ongoing depletion of fossil energy, alternative energy-sources and their respective conversion technologies have become very essential. An inexhaustible and clean energy form, which is already widely used, is solar energy. However, despite much progress in recent decades, due to the limitations of materials and manufacturing technology, the ability of solar cells to convert light into electrical energy is still not very high. Enhancing light absorption and reducing electric loss are the keys to improving the overall conversion efficiency of solar cells and reducing raw material costs. The former can be achieved by using micro/nanostructures and other surface features, while the latter can be realized by surface passivation. Researchers have developed different silicon-surface texturing methods to fabricate random or periodic micro/nanostructures on the surface of silicon wafers. Thanks to the special and efficient light-trapping effects of silicon micro/nanostructures, both full angle and wideband light absorption can be achieved. Different passivation methods and materials have also been widely studied, which helps to improve the surface recombination of photogenerated carriers caused by light trapping structure and significantly enhance the power conversion efficiency of Si solar cells. In this work, theoretical studies of enhanced light-trapping in micro/nanostructures are introduced. In addition, several advanced methods for preparing micro/nanostructures on the surface of monocrystalline silicon are discussed. These can be classified as top-down and bottom-up approaches. Furthermore, passivation methods for micro/nanostructures on the surface of monocrystalline silicon solar cells are reviewed, including chemical passivation and field-effect passivation. Finally, advantages and disadvantages of the micro/nanostructure preparation technologies, and light-trapping effects of the micro/nanostructures, which were fabricated using these manufacturing technologies were summarized. Moreover, the effects of different passivation technologies on the optical properties and electrical properties of these micro/nanostructures are studied. An outlook of expected and emerging research directions for monocrystalline silicon solar cells concludes this study.