Investigation of Lossy-Film-Induced Optical Effects for Maximum Transmittance into Absorption Layers of Thin-Film Solar Cells

• Main Authors: Chi-Sheng Lai, 賴啟勝
• Other Authors: Yin-Jung Chang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/37851851014144858124

碩士 === 國立中央大學 === 光電科學與工程學系 === 101 === In this research, we investigate lossy-film-induced optical effects for a maximum average transmittance into absorption layers of thin-film solar cells. Using the transfer matrix method incorporated with the Poynting theorem successfully calculates optical transmittance passing through an arbitrary interface in multilayered structure. In a single lossy film case, we show that the film thickness at which the reflectance minimum occurs does not coincide at the same thickness as having a maximum transmittance. In general, when the extinction coefficient of the film is gradually increased, the reflectance minima moves toward smaller values of film thickness while the transmittance maximum shifts in the opposite direction. As the incident angle is increased, the maximum extinction coefficient at which the maximum transmittance still exists at a non-zero film thickness increases for TE waves. In contrast, TM waves behave just oppositlely. Since the interlayers of a typical CIGS solar cell are lossy, using minimum reflectance as the requirement of anti-reflection (AR) coating designs may not be appropriate. Instead, it should be the transmittance penetrating into the absorption layer that may be appropriate as the design criterion. Based on the results described in Chapters two and three, Chapter four reports the optimizations of interlayers and AR coating of a typical CIGS solar cell using simulated annealing (SA) algorithm incorporated with the solar irradiance spectrum for broadband (350 nm ~ 1200 nm) and omnidirectional (0~80) operations. The results show that using a target function of minimum reflectance, the thickness of AZO layer is close to the upper limit of the searching range used in SA. On the contrary, when the target function of maximum transmittance into the absorption layer is used, the AZO layer thickness is close to its lower limit. The optimized interlayers and two-layer AR coating with the maximum transmittance criterion exhibit an average transmittance of >80% and an average reflectance of <3.81%. In contrast, when a minimum reflectance requirement is used, the optimized results show an average reflectance of <2.45%, but the average transmittance is only 57.36%. When taking the solar spectrum weighting (SSW) into consideration, both target functions can result in a smaller reflectance and higher transmittance over the wavelengths with stronger solar irradiance, although the differences in the transmittance between designs with and without the SSW are subtle for the minimum reflectance designs due to a thicker AZO layer thickness.