Defect-mediated metastability and carrier lifetimes in polycrystalline (Ag,Cu)(In,Ga)Se2 absorber materials

Ferguson, Andrew J.; Farshchi, Rouin; Paul, Pran K.; Dippo, Pat; Bailey, Jeff; Poplavskyy, Dmitry; Khanam, Afrina; Tuomisto, Filip; Arehart, Aaron R.; Kuciauskas, Darius

doi:10.1063/1.5134502

Defect-mediated metastability and carrier lifetimes in polycrystalline (Ag,Cu)(In,Ga)Se₂ absorber materials

Journal Article · Tue Jun 02 00:00:00 EDT 2020 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.5134502· OSTI ID:1660034

^[1]; Farshchi, Rouin ^[2]; Paul, Pran K. ^[3]; Dippo, Pat ^[1]; Bailey, Jeff ^[2]; Poplavskyy, Dmitry ^[2]; ^[4]; ^[5]; ^[3]; ^[1]

National Renewable Energy Lab. (NREL), Golden, CO (United States)
MiaSolé Hi-Tech Corp., Santa Clara, CA (United States)
The Ohio State Univ., Columbus, OH (United States)
Aalto Univ., Otaniemi (Finland)
Aalto Univ., Otaniemi (Finland); Univ. of Helsinki (Finland)

Using a combination of optical and electrical measurements, we develop a model for metastable defects in Ag-alloyed Cu(In,Ga)Se₂, one of the leading thin film photovoltaic materials. By controlling the pre-selenization conditions of the back contact prior to the growth of polycrystalline (Ag,Cu)(In,Ga)Se₂ absorbers and subsequently exposing them to various stresses (light soaking and dark-heat), we explore in this paper the nature and role of metastable defects on the electro-optical and photovoltaic performance of high-efficiency solar cell materials and devices. Positron annihilation spectroscopy indicates that dark-heat exposure results in an increase in the concentration of the selenium–copper divacancy complex (V_Se–V_Cu), attributed to depassivation of donor defects. Deep-level optical spectroscopy finds a corresponding increase of a defect at Ev+0.98 eV, and deep-level transient spectroscopy suggests that this increase is accompanied by a decrease in the concentration of mid-bandgap recombination centers. Time-resolved photoluminescence excitation spectroscopy data are consistent with the presence of the V_Se–V_Cu divacancy complex, which may act as a shallow trap for the minority carriers. Light-soaking experiments are consistent with the V_Se–V_Cu optical cycle proposed by Lany and Zunger, resulting in the conversion of shallow traps into recombination states that limit the effective minority carrier recombination time (and the associated carrier diffusion length) and an increase in the doping density that limits carrier extraction in photovoltaic devices.

View Accepted Manuscript (DOE)

Research Organization:: National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Sponsoring Organization:: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office

Grant/Contract Number:: AC36-08GO28308; EE0008755

OSTI ID:: 1660034

Alternate ID(s):: OSTI ID: 1808793
OSTI ID: 1631481

Report Number(s):: NREL/JA-5900-75301; MainId:6622; UUID:95c219d5-c9fa-e911-9c29-ac162d87dfe5; MainAdminID:13799

Journal Information:: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 21 Vol. 127; ISSN 0021-8979

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Ag-alloyed Cu(In
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Defect-mediated metastability and carrier lifetimes in polycrystalline (Ag,Cu)(In,Ga)Se2 absorber materials

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Defect-mediated metastability and carrier lifetimes in polycrystalline (Ag,Cu)(In,Ga)Se₂ absorber materials