Stoichiometry-controllable optical defects in CuxIn2−xSy quantum dots for energy harvesting

Addis S. Fuhr; Anastassia N. Alexandrova; Philippe Sautet

doi:10.1039/D0TA03954C

Stoichiometry-controllable optical defects in Cu_xIn_2−xS_y quantum dots for energy harvesting†

Addis S. Fuhr,

^ab Anastassia N. Alexandrova

*^cd and Philippe Sautet

*^acd

Author affiliations

* Corresponding authors

^a Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California 90095, USA
E-mail: sautet@ucla.edu

^b Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

^c Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
E-mail: ana@chem.ucla.edu

^d California NanoSystems Institute, University of California, Los Angeles, California 90095, USA

Abstract

The large Stokes shift for Cu_xIn_2−xS_y (CIS) quantum dots (QDs) reduces reabsorption losses in luminescent solar concentrators (LSCs). However, reabsorption still occurs due to their broad absorption spectra, which, along with below unity quantum yields, hamper device performance. The origin of these optical properties is heavily debated, and makes it difficult to optimize CIS for LSCs and other energy harvesting devices such as solid-state and sensitized solar cells. Here, we show with density functional theory calculations that anti-site defects Image ID:d0ta03954c-t1.gif form in near-stoichiometric CIS QDs, while copper vacancies charge-compensated by the oxidation of a second Cu atom Image ID:d0ta03954c-t2.gif form in Cu-deficient structures. Both defects lead to large Stokes shifts, but Image ID:d0ta03954c-t3.gif defects only localize holes in the excited-state leading to strong intragap absorption, which is suppressed for paramagnetic Image ID:d0ta03954c-t4.gif defects that localize holes in the ground-state. The relative concentration of each defect and competing defect phases that lead to non-emissive carrier trapping is controllable by stoichiometry and Fermi-level, and optimal chemical processing conditions for energy harvesting applications are discussed.

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Article information

DOI: https://doi.org/10.1039/D0TA03954C
Article type: Paper
Submitted: 11 Apr 2020
Accepted: 09 Jun 2020
First published: 10 Jun 2020

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J. Mater. Chem. A, 2020,8, 12556-12565

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Stoichiometry-controllable optical defects in Cu_xIn_2−xS_y quantum dots for energy harvesting

A. S. Fuhr, A. N. Alexandrova and P. Sautet, J. Mater. Chem. A, 2020, 8, 12556 DOI: 10.1039/D0TA03954C

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Journal of Materials Chemistry A