Title
Alkali treatment for single-stage co-evaporated thin CuIn0.7Ga0.3Se2 solar cells
Author
de Wild, J.
Simor, M.
Buldu, D.G.
Kohl, T.
Brammertz, G.
Meuris, M.
Poortmans, J.
Vermang, B.
Publication year
2019
Abstract
KF and NaF treatments were done for single-stage co-evaporated CuIn0.7Ga0.3Se2. The absorber layers were grown on a substrate with an alkali barrier layer and NaF was either added before or after absorber layer growth. No differences were found on the device performance amongst the procedures to add Na. This is expected if the single-stage process does not have a copper rich stage or a Ga gradient, which is likely since there was no change of the elemental fluxes during absorber layer growth and no Ga profile was measured. KF was added by post-deposition only. Current-voltage characteristics were measured and net doping concentrations were determined from capacitance-voltage measurements . We see an improvement of the open-circuit voltage with increasing KF amount, and a marginal increase of the fill factor. CV measurements showed increasing net acceptor concentration with increasing KF amount. Time resolved photoluminescence showed an increased decay time for KF treated cells and the PL peak shape changed. Without KF treatment the PL peak is symmetric, after KF treatment a further peak appears at higher energy in the PL spectrum. This higher energy peak increases in intensity with increasing KF concentration. The same effects were seen in a sample without Na, but here the Voc was limited due to large tailing. Hence both Na and K are required for good cell efficiencies. © 2018 Elsevier B.V.
Subject
Alkali treatment
Co-evaporation
Copper indium gallium selenide
Single-stage
Solar cells
Thin film
To reference this document use:
http://resolver.tudelft.nl/uuid:237c0d4d-a859-4ddf-9415-f04279ca1e3c
TNO identifier
844233
ISSN
0040-6090
Source
Thin Solid Films, 671, 44-48
Document type
article