Back-Surface Passivation of CdTe Solar Cells Using Solution-Processed Oxidized Aluminum

Fadhil K. Alfadhili, Adam B. Phillips, Kamala Khanal Subedi, Craig L. Perkins, Adam I. Halaoui, Manoj K. Jamarkattel, Bhuiyan M. Anwar, Geethika K. Liyanage, Deng Bing Li, Corey R. Grice, Yanfa Yan, Randy J. Ellingson, Michael J. Heben

Research output: Contribution to journalArticlepeer-review

15 Scopus Citations

Abstract

Although back-surface passivation plays an important role in high-efficiency photovoltaics, it has not yet been definitively demonstrated for CdTe. Here, we present a solution-based process, which achieves passivation and improved electrical performance when very small amounts of oxidized Al3+ species are deposited at the back surface of CdTe devices. The open circuit voltage (Voc) is increased and the fill factor (FF) and photoconversion efficiency (PCE) are optimized when the total amount added corresponds to ∼1 monolayer, suggesting that the passivation is surface specific. Addition of further Al3+ species, present in a sparse alumina-like layer, causes the FF and PCE to drop as the interface layer becomes blocking to current flow. The optimized deposit increases the average baseline PCE for both Cu-free devices and devices where Cu is present as a dopant. The greatest improvement is found when the Al3+ species are deposited prior to the CdCl2 activation step and Cu is employed. In this case, the best-cell efficiency was improved from 12.6 to 14.4%. Time-resolved photoluminescence measurements at the back surface and quantum efficiency measurements performed at the maximum power point indicate that the performance enhancement is due to a reduction in the interface recombination current at the back surface.

Original languageAmerican English
Pages (from-to)51337-51343
Number of pages7
JournalACS Applied Materials and Interfaces
Volume12
Issue number46
DOIs
StatePublished - 18 Nov 2020

Bibliographical note

Publisher Copyright:
© 2020 American Chemical Society.

NREL Publication Number

  • NREL/JA-5K00-78458

Keywords

  • alumina
  • back contact
  • CdTe
  • interface passivation
  • solution processed

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