The role of oxygen doping on elemental intermixing at the PVD-CdS/Cu (InGa)Se2 heterojunction

He, Xiaoqing; Ercius, Peter; Varley, Joel B.; Bailey, Jeff; Zapalac, Geordie; Nagle, Tim; Poplavskyy, Dmitry; Mackie, Neil; Bayman, Atiye; Lordi, Vincenzo; Rockett, Angus

doi:10.1002/pip.3087

Title: The role of oxygen doping on elemental intermixing at the PVD-CdS/Cu (InGa)Se₂ heterojunction

Journal Article · Thu Dec 20 00:00:00 EST 2018 · Progress in Photovoltaics

DOI:https://doi.org/10.1002/pip.3087· OSTI ID:1515358

^[1]; Ercius, Peter ^[2]; Varley, Joel B. ^[3]; Bailey, Jeff ^[4]; Zapalac, Geordie ^[4]; Nagle, Tim ^[4]; Poplavskyy, Dmitry ^[4]; Mackie, Neil ^[4]; Bayman, Atiye ^[4]; Lordi, Vincenzo ^[3]; Rockett, Angus ^[5]

University of Illinois at Urbana‐Champaign, Urbana, IL (United States); Univ. of Missouri, Columbia, MO (United States)
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
MiaSolé Hi‐Tech, Santa Clara, CA (United States)
University of Illinois at Urbana‐Champaign, Urbana, IL (United States); Colorado School of Mines, Golden, CO (United States)

Elemental intermixing at the CdS/CuIn_1-xGa_xSe₂ (CIGS) heterojunction in thin-film photovoltaic devices plays a crucial role in carrier separation and thus device efficiency. Here, using scanning transmission electron microcopy in combination with energy dispersive X-ray mapping, we find that by controlling the oxygen in the sputtering gas during physical vapor deposition (PVD) of the CdS, we can tailor the degree of elemental intermixing. More oxygen suppresses Cu migration from the CIGS into the CdS, while facilitating Zn doping in the CdS from the ZnO transparent contact. Very high oxygen levels induce nanocrystallinity in the CdS, while moderate or no oxygen content can promote complete CdS epitaxy on the CIGS grains. Regions of cubic Cu₂S phase were observed in the Cu-rich CdCuS when no oxygen is included in the CdS deposition process. In the process-of-record sample (moderate O₂) that exhibits the highest solar conversion efficiency, we observe a ~26-nm-thick Cu-deficient CIGS surface counter-doped with the highest Cd concentration among all of the samples. Cd movement into the CIGS was found to be less than 10 nm deep for samples with either high or zero O₂ . Lastly, the results are consistent with the expectation that Cd doping of the CIGS surface and lack of Zn diffusion into the buffer both enhance device performance.

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Research Organization:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division; USDOE Office of Energy Efficiency and Renewable Energy (EERE)

Grant/Contract Number:: AC52-07NA27344; AC02-05CH11231; AC52‐07NA27344; DE‐AC02‐05CH11231

OSTI ID:: 1515358

Alternate ID(s):: OSTI ID: 1506409; OSTI ID: 1786624

Report Number(s):: LLNL-JRNL-751864; 937854

Journal Information:: Progress in Photovoltaics, Vol. 27, Issue 3; ISSN 1062-7995

Publisher:: WileyCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 4 works

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Title: The role of oxygen doping on elemental intermixing at the PVD-CdS/Cu (InGa)Se2 heterojunction

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Title: The role of oxygen doping on elemental intermixing at the PVD-CdS/Cu (InGa)Se₂ heterojunction