Photon management in nanostructured solar cells Hsin-Ping Wang, a Der-Hsien Lien, a Meng-Lin Tsai, a Chin-An Lin, a Hung-Chih Chang, a Kun-Yu Lai b and Jr-Hau He * a The unique geometry and intriguing physical properties of nanostructure-based solar cells gives them great potential to achieve the goals of cost-effectiveness and high-efficiency. With nanostructured solar cells it is expected to be possible to break the Shockley–Queisser limit. This potential has driven widespread research and development in photon management to enhance light absorption over the past decade. However, efficiency is not proportional to light absorption. Nowadays, researchers are starting to address this issue. A thorough understanding of the advantages and the scope of the application of each photon management scheme is critical to finding a breakthrough for this predicament. In this review, we present the theorems and describe recent progresses in primary photon management schemes for nanostructures, including antireflection, light scattering, and resonance (e.g., metallic resonance, dielectric resonance, and photonic crystals). The antireflection effect allows more light to enter the solar cell. Light scattering enhances the interaction between the light and the nanostructure, extending the light propagation paths in the devices. Resonance effects can redirect and precisely confine the light to the region where efficient photoelectric conversion efficiency occurs. Finally, we discuss the challenges of nanostructured solar cells, and indicate potential routes to overcome the performance-limiting problems. 1. Introduction With the rapid growth of the human population over the past decades, there has been a steep increase in the global demand for electricity. The demand is expected to be even greater by the year 2100 (46 teraWatt, TW), more than three times the global power consumption today (16 TW). 1 An even worse problem that comes with extravagant energy consumption are the associated environmental issues. Based on the latest investigations, the global energy-related CO 2 emissions reached a historic high of 31.6 gigatonnes in 2012, which is regarded as a suspected cause of serious climate change. 2 To counteract against such prob- lems, the expansion of clean power production methods is indispensable. It is estimated that by 2035 one-third of the total electricity output should be generated from renewable energy. 3 Hsin-Ping Wang received her M.S. degree (2011) at the Grad- uate Institute of Photonics and Optoelectronics at the National Taiwan University, Taipei, Tai- wan. She is now a Ph.D. student in Dr Jr-Hau He's group. Her research interests include theo- retical and experimental research on the optical proper- ties analysis of nanostructures and solar cells (including conventional Si solar cells, thin- lm solar cells, a-Si solar cells, and Si heterojunction solar cells), and solar water splitting cells. Der-Hsien Lien received his B.S. degree (2003) and M.S. degree (2005) at the Department of Materials Science and Engi- neering from the National Tsing Hua University, Hsinchu, Tai- wan. He is a Ph.D. student at the Institute of Photonics and Opto- electronics at the National Tai- wan University. His research interests include the dynamics and applications of nano- photonics, green memory devices, 2D materials physics and exible optoelectronics. a Institute of Photonics and Optoelectronics & Department of Electrical Engineering, National Taiwan University, Taipei 106, Taiwan. E-mail: jhhe@cc.ee.ntu.edu.tw; Fax: +886-2-23677467; Tel: +886-2-33669646 b Department of Optics and Photonics, National Central University, Chung-Li 320, Taiwan Cite this: J. Mater. Chem. C, 2014, 2, 3144 Received 18th October 2013 Accepted 12th February 2014 DOI: 10.1039/c3tc32067g www.rsc.org/MaterialsC 3144 | J. Mater. Chem. C, 2014, 2, 3144–3171 This journal is © The Royal Society of Chemistry 2014 Journal of Materials Chemistry C FEATURE ARTICLE Published on 14 February 2014. Downloaded by King Abdullah Univ of Science and Technology on 23/11/2014 12:22:21. View Article Online View Journal | View Issue