Optical absorption spectra of thin film solar cell semiconductors with a composition gradient by a photothermal spectroscopy

2015 Fiscal Year Final Research Report

• Project/Area Number: 25390082
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Thin film/Surface and interfacial physical properties
• Research Institution: University of Miyazaki
• Principal Investigator: IKARI TETSUO 宮崎大学, 工学部, 研究員 (70113214)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 半導体光物性 / 薄膜結晶成長 / 無発光電子再結合 / 量子構造半導体

Outline of Final Research Achievements

Nonradiative electron transition of the photo excited electron carriers in chalcopyrite CIGS thin films with composition gradient near the buffer and absorption layer were investigate by using our renovated high sensitivity piezoelectric photothermal spectral (PPTS) measurements. Although this compositional gradient is necessary for manufacturing the high efficiency solar cells, we had no experimental methodology to make clear the electronic structures until now. In this project, the effect of the compositional gradient was discussed from both the PPT experiments and theoretical prediction. The observed decrease of the absorption edge was explained by the presence of Cd impurities diffused from the buffer layer during the growth. Since the first approximation model cannot explain the observed experimental results, we found that the carrier diffusion should be taken into account in the heat diffusion equation.

Free Research Field

半導体の材料物性と太陽電池への応用