成果報告書詳細
管理番号20160000000270
タイトル*平成27年度中間年報 高性能・高信頼性太陽光発電の発電コスト低減技術開発 太陽電池セル、モジュールの共通基盤技術開発 CIS太陽電池高性能化技術の研究開発(積層構造・改質界面の電子構造評価による電池特性向上技術の開発)
公開日2016/12/10
報告書年度2015 - 2015
委託先名国立大学法人鹿児島大学
プロジェクト番号P15003
部署名新エネルギー部
和文要約
英文要約Title: Development of key technologies for high-efficiency CIS solar cells (Development of technologies for high cell-performances based on characterization of the layered structure and the modified interface) (FY2015-FY2017) FY2015 Annual Report

1. Objectives: Electronic structures of hetero interfaces and modified surface of the Cu(In, Ga)(S, Se)2 [CIGSSe]absorber are to be investigated for developing key technologies for higher conversion efficiency in CIGSSe based cells. Correlations between these characteristics and fabrication parameters and guiding principle for process-optimization are to be clarified. 2. For FY 2015 (1) Development of the surface cleaning method for the CIGSSe films fabricated in separated institutes and determination of their intrinsic nature: The adoption of Ar ion beam with a kinetic energy below 50 eV has yielded the development of the CIGSSe surface without contamination and chemical modification. The treated surface consists of the Cu-deficient chalcopyrite phase with S/(S_Se) of about 0.55 and band gap energy of 1.3-1.45 eV. This surface is also characterized by the absence of the so-called ordered vacancy compound. A conduction band minimum of the cleaned CZTSSe is high about 0.85-0.90 eV, which is originated in the S substitution. (2) Determination of electronic structure of the interface between CdS buffer and the clean CIGSSe: The band alignment at the CdS/CIGSSe interface has been determined by in-situ photoemission spectroscopy (XPS, IPES) and inverse photoemission spectroscopy (IPES). A deposition of the 50 nm thick CdS resulted in a decrease of CBM and valence band maximum VBM by 0.4 and 1.5 eV, respectively. Changes in binding energies of the XPS core signals in conjunction with CdS thickness show that the interface induced band bending of this interface is downward and large about 0.44 eV. The conduction band offset (CBO) derived from these values is slightly positive: CBO=-0.4 ~ +0.05 eV. This result has revealed that the conduction band alignment at this interface is flat or small spike, in spite of the high CBM of the CIGSSe-side. It is the favorable band alignment for suppressing interface-recombination without blocking the electron transport. It is, therefore, consistent with the fact that the cells using the identically prepared CIGSSe show excellent performances such as a conversion efficiency of above 20%. (3)Integration of a deposition system of window layer with the XPS/UPS/IPES system: A multi-target sputtering system equipped with a ZnO and Al-doped ZnO (AZO) has been combined with the analysis system. The AZO films with a sufficiently low resistivity below 1 milli-Ohm*cm is obtained at a growth temperature below 150 degree centigrade. The latter is low enough to maintain original nature of the CdS/CIGSSe underlying interface. These results mean that the technological requirements for the in-situ evaluation of intrinsic nature of the window/buffer interface are established.
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