Using hole injection layers for decreased metastability and higher performance in Cu(In,Ga)Se2 devices

• Published in: Solar energy materials and solar cells 2020-09, Vol.215 (C), p.110597, Article 110597
• Main Authors: Repins, Ingrid, Glynn, Stephen, Bowers, Karen, Stevens, Bart, Perkins, Craig L., Mansfield, Lorelle
• Format: Article
• Language: English
• Subjects: Buffers; Conductors; Copper indium gallium selenides; Energy conversion efficiency; Injection; Metastable state; Photovoltaic cells; Solar cells; Thin films; Zinc
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2020.110597

Modifications to the buffer structure in Cu(In,Ga)Se2 (CIGS) solar cells are examined in terms of power conversion efficiency and metastability. Varying amounts of thin hole-injecting layers are introduced at different locations in the CIGS/Zn(O,S) device structure. It is found that such layers simultaneously increase performance and decrease metastability. The most effective variant produces devices without metastability and with higher efficiency than the CdS-only controls. The most effective location for hole injection is found to be between the Zn(O,S) buffer and the transparent conductor. At this location, passivation of the CIGS surface is not a function of the hole injection layer, and thus a variety of materials with appropriate band-edge energies should achieve the same purpose. •Metastability and efficiency improve when adding thin CdS to either side of a Zn(O,S) buffer in a CIGS solar cell.•Benefits are larger when injecting holes from the light side of the Zn(O,S) than from the CIGS side of the Zn(O,S).•Any material that can be used to inject holes (not just CdS) is expected to work in a similar manner.•The most effective buffer variant produces cells without metastability and with higher efficiency than the standard CdS.