Properties of Cu1–xKxInSe2 alloys
- Univ. of Florida, Gainesville, FL (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States). National Center for Photovoltaics
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Univ. of Florida, Gainesville, FL (United States)
Adding potassium to Cu(In,Ga)Se2 absorbers has been shown to enhance photovoltaic power conversion efficiency. To illuminate possible mechanisms for this enhancement and limits to beneficial K incorporation, the properties of Cu1-xKxInSe2 (CKIS) thin-film alloys have been studied. Films with K/(K + Cu), or x, from 0 to 1 were grown by co-evaporation, and probed by XRF, EPMA, SEM, XRD, UV-Visible spectroscopy, current-voltage, and TRPL measurements. Composition from in situ quartz crystal and EIES monitoring was well correlated with final film composition. Crystal lattice parameters showed linear dependence on x, indicating complete K incorporation and coherent structural character at all compositions in the <100> and <010> lattice directions, despite the different symmetries of CuInSe2 and KInSe2. The band gap energy showed pronounced bowing with x composition, in excellent agreement with experimental reports and semiconductor theory. Films of Mo/CKIS/Ni were non-ohmic, and increasing x from 0 to 0.58 decreased the apparent CKIS resistivity. Further evidence of decreased CKIS resistivity was observed with photoluminescence response, which increased by about half a decade for x > 0, and indicates increased majority carrier concentration. Minority carrier lifetimes increased by about an order of magnitude for films grown at x = 0.07 and 0.14, relative to CuInSe2 and x ≥ 0.30. As a result, this is the first report of a Cu-K-In-Se film with >1 at.% K, and the observed property changes at increased x (wider band gap; lower resistivity; increased lifetime) comprise valuable photovoltaic performance-enhancement strategies, suggesting that CKIS alloys have a role to play in future engineering advances.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office; SunShot Foundational Program to Advance Cell Efficiency (F-PACE)
- Grant/Contract Number:
- AC36-08GO28308; FOA-0000492
- OSTI ID:
- 1329988
- Report Number(s):
- NREL/JA-5K00-67323
- Journal Information:
- Journal of Materials Science, Vol. 51, Issue 14; ISSN 0022-2461
- Publisher:
- SpringerCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Similar Records
Chemistry of K in Cu(In,Ga)Se2 photovoltaic absorbers: Effects of temperature on Cu-K-In-Se films
Surface and bulk effects of K in highly efficient Cu1-xKxInSe2 solar cells