Locating the electrical junctions in Cu(In,Ga)Se2 and Cu2ZnSnSe4 solar cells by scanning capacitance spectroscopy
- National Renewable Energy Lab. (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- The Univ. of Toledo, Toledo OH (United States)
- Colorado School of Mines, Golden CO (United States)
Abstract We determined the electrical junction (EJ) locations in Cu(In,Ga)Se 2 (CIGS) and Cu 2 ZnSnSe 4 (CZTS) solar cells with ~20‐nm accuracy by developing scanning capacitance spectroscopy (SCS) applicable to the thin‐film devices. Cross‐sectional sample preparation for the SCS measurement was developed by high‐energy ion milling at room temperature for polishing the cross section to make it flat, followed by low‐energy ion milling at liquid nitrogen temperature for removing the damaged layer and subsequent annealing for growing a native oxide layer. The SCS shows distinct p‐type, transitional, and n‐type spectra across the devices, and the spectral features change rapidly with location in the depletion region, which results in determining the EJ with ~20‐nm resolution. We found an n‐type CIGS in the region next to the CIGS/CdS interface; thus, the cell is a homojunction. The EJ is ~40 nm from the interface on the CIGS side. In contrast, such an n‐type CZTS was not found in the CZTS/CdS cells. The EJ is ~20 nm from the CZTS/CdS interface, which is consistent with asymmetrical carrier concentrations of the p‐CZTS and n‐CdS in a heterojunction cell. Our results of unambiguously determination of the junction locations contribute significantly to understanding the large open‐circuit voltage difference between CIGS and CZTS. Copyright © 2016 John Wiley & Sons, Ltd.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- Grant/Contract Number:
- AC36-08GO28308; DE‐AC36‐08GO28308
- OSTI ID:
- 1336560
- Alternate ID(s):
- OSTI ID: 1464550
- Report Number(s):
- NREL/JA-5K00-65634
- Journal Information:
- Progress in Photovoltaics, Vol. 25, Issue 1; ISSN 1062-7995
- Publisher:
- WileyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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