Reducing Interface Recombination for Cu(In,Ga)Se2 by Atomic Layer Deposited Buffer Layers

Adam Hultqvist, Jian V. Li, Darius Kuciauskas, Patricia Dippo, Miguel A. Contreras, Dean H. Levi, Stacey F. Bent

Research output: Contribution to journalArticlepeer-review

21 Scopus Citations

Abstract

Partial CuInGaSe2 (CIGS) solar cell stacks with different atomic layer deposited buffer layers and pretreatments were analyzed by photoluminescence (PL) and capacitance voltage (CV) measurements to investigate the buffer layer/CIGS interface. Atomic layer deposited ZnS, ZnO, and SnOx buffer layers were compared with chemical bath deposited CdS buffer layers. Band bending, charge density, and interface state density were extracted from the CV measurement using an analysis technique new to CIGS. The surface recombination velocity calculated from the density of interface traps for a ZnS/CIGS stack shows a remarkably low value of 810 cm/s, approaching the range of single crystalline II-VI systems. Both the PL spectra and its lifetime depend on the buffer layer; thus, these measurements are not only sensitive to the absorber but also to the absorber/buffer layer system. Pretreatment of the CIGS prior to the buffer layer deposition plays a significant role on the electrical properties for the same buffer layer/CIGS stack, further illuminating the importance of good interface formation. Finally, ZnS is found to be the best performing buffer layer in this study, especially if the CIGS surface is pretreated with potassium cyanide.

Original languageAmerican English
Article numberArticle No. 033906
Number of pages5
JournalApplied Physics Letters
Volume107
Issue number3
DOIs
StatePublished - 20 Jul 2015

Bibliographical note

Publisher Copyright:
© 2015 AIP Publishing LLC.

NREL Publication Number

  • NREL/JA-5J00-64964

Keywords

  • atomic layer deposition
  • buffer layers
  • II-VI semiconductors
  • photoluminescence
  • solar cells

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