On optical reflection at heterojunction interface of thin film solar cells

• Published in: Solar energy materials and solar cells Vol. 111; pp. 141 - 145
• Main Authors: Zhu, L., Luo, J.K., Shao, G., Milne, W.I.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.04.2013; Elsevier
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Energy; Exact sciences and technology; Gallium arsenide; Heterojunctions; Heterostructure solar cells; Heterostructures; Indium tin oxide; Interface; Internal reflection; Natural energy; Photoelectric conversion; Photovoltaic cells; Photovoltaic conversion; Reflection; Semiconductors; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Thin films; Heterostructure solar cells; Interface; Internal reflection; Binary compound; Semiconductor materials; Conversion rate; Ge-Si alloys; Refraction index; Polymer; Indium oxide; Indium phosphide; Photovoltaic cell; Solar cell; Degradation; Crystalline material; Tin addition; Thin film cell; Homojunction; Window layer; Optical reflection; Heterostructures; Damaging; Heterojunction
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2012.12.035

Heterojunction is an important structure for the development of photovoltaic solar cells. In contrast to homojunction structures, heterojunction solar cells have internal crystalline interfaces, which will reflect part of the incident light, and this has not been considered carefully before though many heterostructure solar cells have been commercialized. This paper discusses the internal reflection for various material systems used for the development of heterostructure-based solar cells. It has been found that the most common heterostructure solar cells have internal reflection less than 2%, while some potential heterojunction solar cells such as ITO/GaAs, ITO/InP, Si/Ge, polymer/semiconductors and oxide semiconductors may have internal reflection as high as 20%. Also it is worse to have a window layer with a lower refractive index than the absorption layer for solar cells. Ignoring this strong internal reflection will lead to severe deterioration and reduction of conversion efficiency; therefore measures have to be taken to minimize or prevent this internal reflection. ► There exists a strong internal optical reflection at the interface of heterojunction cells. ► Internal reflection could be well over 20% if the refractive indices are very different. ► Internal reflection will cause severe reduction of solar cell efficiency. ► A large error could be produced for cells by simulation if permittivity not refractivity is used.