Defects in Cu(In, Ga) Se2 semiconductors and their role in the device performance of thin-film solar cells

Impact of bulk properties and local secondary phases on the Cu2(Zn,Sn)Se4 solar cells open-circuit voltage

“…The CdS is assumed to be highly compensated, with n-type doping comparable to the defect density. The defects in CdS are acceptor type (the capture cross section for electrons is much smaller than for holes) [34]. The carrier mobilities in the CZTSe absorber layers were estimated based on the calculated effective masses of CZTSe.…”

Photo current metastability in Cu(In,Ga)Se2 solar cells with controlled conduction band alignment

“…Thus, the collection of the photo current would be affected by the white light exposure. This may be due to a surface n-type inversion by Cu migration [2] or an increase in hole carrier density in the CIGS layer [7] which lead the decrease in the effective barrier height of the ZMO/CIGS layers after white light exposure. In contrast, the CIGS solar cells with CdPE treatment showed the negligible LS effect.…”

“…This effect causes some issues such as the increase of manufacturing processes due to the long exposure to white light under constant temperature and the vagueness of the standard for the measurement raised by the change in the efficiency due to whether a solar cell is irradiated preliminarily or not. Models for the generation mechanism of the LS effect such as the migration of copper atoms [2] and the persistent photoconductivity of the CIGS layer [3] were proposed, however the mechanism has not been clarified fully. We have recently proposed that the key factor for the LS effect would be the buffer (window)/CIGS heterointerface.…”

Metastability of Zn1−xMgxO/Cu(In,Ga)Se2 solar cells with different conduction band offset values

“…This effect causes some issues such as the increase of manufacturing processes due to the long exposure to white light under constant temperature and the vagueness of the standard for the measurement raised by the change in the efficiency due to the fact that whether a solar cell is irradiated preliminarily or not. Models for the generation mechanism of the LS effect such as the migration of copper atoms [4] and the persistent photoconductivity of the CIGS layer [5] were proposed; however, the mechanism has not been clarified fully. The key factor for the LS effect would be the buffer (window)/CIGS heterointerface, especially conduction band offset (CBO) judging from the report that the LS effect is affected by the buffer layer [6].…”