skip to main content


This content will become publicly available on February 27, 2019

Title: The effect of Na on Cu-K-In-Se thin film growth

Co-evaporation of Cu-KF-In-Se was performed on substrates with varied Na supply. Compositions of interest for photovoltaic absorbers were studied, with ratios of (K + Cu)/In ~ 0.85 and K/(K + Cu) ~ 0-0.57. Bare soda-lime glass (SLG) substrates had the highest Na supply as measured by secondary ion mass spectrometry, while SLG/Mo and SLG/SiO 2/Mo substrates led to 3x and 3000x less Na in the growing film, respectively. Increased Na supply favored Cu 1-xK xInSe 2 (CKIS) alloy formation as proven by X-ray diffraction (XRD), while decreased Na supply favored the formation of CuInSe 2 + KInSe 2 mixed-phase films. Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed the KInSe 2 precipitates to be readily recognizable planar crystals. Extrinsic KF addition during film growth promoted diffusion of Na out from the various substrates and into the growing film, in agreement with previous reports. Time-resolved photoluminescence showed enhanced minority carrier lifetimes for films with moderate K compositions (0.04 < K/(K + Cu) < 0.14) grown on SLG/Mo. Due to the relatively high detection limit of KInSe 2 by XRD and the low magnitude of chalcopyrite lattice shift for CKIS alloys with these compositions, it is unclear if the lifetime gainsmore » were associated with CKIS alloying, minor KInSe 2 content, or both. The identified Na-K interdependency can be used to engineer alkali metal bonding in Cu(In,Ga)(Se,S) 2 absorbers to optimize both initial and long-term photovoltaic power generation.« less
 [1] ;  [2] ;  [3]
  1. Univ. of Florida, Gainesville, FL (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Univ. of Florida, Gainesville, FL (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Univ. of Florida, Gainesville, FL (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0022-0248
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Crystal Growth
Additional Journal Information:
Journal Volume: 488; Journal Issue: C; Journal ID: ISSN 0022-0248
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
Country of Publication:
United States
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; crystal morphology; segregation; solid solutions; physical vapor deposition processes; alloys; semiconducting materials
OSTI Identifier: