Review of Grain Interior, Grain Boundary, and Interface Effects of K in CIGS Solar Cells: Mechanisms for Performance Enhancement

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Abstract

Introducing K into Cu(In,Ga)(Se,S)2 (CIGS) absorbers has led to recent world record power conversion efficiencies for thin film polycrystalline solar cells. In this work, the diverse phenomena associated with K in CIGS were reviewed, and overarching mechanisms were identified. The effects of K depend on its distribution among grain interiors (GIs), grain boundaries (GBs), and interfaces. High substrate Na and low temperature favor GI K incorporation, while low Na and high temperature favor segregation of K at GBs. Depositing KInSe2 (or KIn1−yGaySe2) by co-evaporation or KF post-deposition treatment onto CIGS reduces buffer interface recombination in the final solar cells. KInSe2 decomposes in air, which makes characterization difficult and may affect performance. The mechanism for reduced interface recombination could be direct passivation, beneficial compound precursor, oxidation barrier, or favorable diffusion alteration.

Original languageAmerican English
Pages (from-to)18-24
Number of pages7
JournalSolar Energy Materials and Solar Cells
Volume172
DOIs
StatePublished - Dec 2017

Bibliographical note

Publisher Copyright:
© 2017 Elsevier B.V.

NREL Publication Number

  • NREL/JA-5K00-68981

Keywords

  • Alkali metal
  • Chalcopyrite
  • Cu(In,Ga)Se
  • K(In,Ga)Se
  • KInSe
  • Potassium

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