| 학회 | 한국재료학회 |
| 학술대회 | 2013년 가을 (11/06 ~ 11/08, 제주롯데호텔) |
| 권호 | 19권 2호 |
| 발표분야 | C. 에너지/환경 재료(Energy and Environmental Materials) |
| 제목 | Analysis of the electronic structure of the Cu(In,Ga)Se2 (CIGS) solar cell and bandoffset |
| 초록 | Cu(In,Ga)Se2 (CIGS) based solar cell is regarded as the most effective thin film solar cell type because only 2 μm thick CIGS film provides the good solar absorption due to its great absorption coefficient. Several research institutions and companies in the current CIGS research in progress reported that CIGS solar cell reaches 20% conversion efficiency, which is higher than that of other thin-film solar cells and close to the efficiency of the existing Si-based solar cells . The layer stacking of CIGS based solar cell consists of bottom electrode/p-type CIGS/buffer layer/n-type intrinsic ZnO/Al-doped ZnO electrode/top electrode. Because of multiple stacked structure of cell, the optimized surface and interface electronic structure is crucial for CIGS/buffer especially. At each interface, the energy loss due to carrier recombination always occurs and thus, acts as main factor for the conversion efficiency reduction. Therefore, the systematic band alignment analysis to know the interface valence band offset and conduction band offset can provides the guideline for the interface design for CIGS based solar cell to improve efficiency. In this presentation, we studied the direct correlation between the efficiency CIGS solar cells and (1) the state of the surface of solar cells (In-final, Ga-final) film on the surface of the electronic band structure and (2) conduction band offset of Zn(O,S) buffer according to S% by X-ray photoelectron spectroscopy. The change of Cu composition near the OVC on the CIGS surface was notably great. After Ar surface sputtering, the Cu 2p peak was shifted to the high binding energy implying the chemical transition from Cu poor at top-surface to Cu rich at the near-surface. In addition, the more the amount of Ga on the surface, the band gap increased. This composition variation leads to the bandgap change probed by cathodoluminescent. At Zn (O, S) buffer, we clearly shows that if S concentration is more than 14% (33, 50, 80%), no solar cell efficiency with CBO at ~ 1 eV is obtained but at 14% of S, CBO was ~ 0.5 eV and conversion efficiency at ~ 14.6 % was obtained. Thus, this strongly suggests that the CBO of buffer layer really acts as a decisive factor for CIGS solar efficiency. |
| 저자 | 엄기령, 유일한, 서형탁 |
| 소속 | 아주대 |
| 키워드 | CIGS; S%; bandoffset; Solarcell |
