Theoretical enhancement of solar cell efficiency by the application of an ideal ‘down-shifting’ thin film

• Published in: Solar energy materials and solar cells Vol. 98; pp. 455 - 464
• Main Authors: Thomas, C.P., Wedding, A.B., Martin, S.O.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-03-2012; Elsevier
• Subjects: Applied sciences; Computational efficiency; Computing time; Detailed balance; Direct energy conversion and energy accumulation; Down-shifting; Efficiency enhancement; Electrical engineering. Electrical power engineering; Electrical power engineering; Energy; Exact sciences and technology; Luminescence; Mathematical analysis; Natural energy; Optical thin films; Photoelectric conversion; Photons; Photovoltaic cells; Photovoltaic conversion; Silicon; Silicon solar cells; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Spectra; Thin films; Efficiency enhancement; Silicon solar cells; Down-shifting; Detailed balance; Optical thin films; Luminescence; Performance evaluation; Conversion rate; Shallow depth; Quantum yield; Standards; Thin film; Photovoltaic cell; Solar cell; Surface recombination; High energy; Charge carrier recombination; Silicon; Optical films
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2011.11.027

Poor ultraviolet (UV) quantum conversion efficiency contributes to a reduction in the efficiency of silicon based photovoltaic cells. In the UV, the main loss mechanism is through surface recombination of photo-generated carriers due to the shallow absorption depth of high energy photons. One method for greater utilisation of the UV region is by down-shifting UV photons to lower energies where the quantum efficiency of silicon is higher. This work determines the potential enhancement in efficiency that can be obtained by a luminescent down-shifting layer applied to silicon based solar cells. The efficiency is determined through detailed balance arguments. The maximum calculated efficiency enhancement due to an ideal down shifting process is 0.6% absolute using the AM1.5G standard spectra. Applying a similar analysis to a multicrystalline silicon solar cell results in an efficiency enhancement due to the down-shifting process of 0.17% absolute.
► Theoretical analysis of UV down-shifting applied to Si solar Cells. ► Efficiency is determined via detailed balance. ► Abeles' relations are used to model multiple optical layers. ► Optical layers are optimised for cell efficiency and down-shifting.