Simulation of metastable changes in time resolved photoluminescence of Cu(In,Ga)Se2 thin film solar cells upon light soaking treatment

Salas, J. F. López; Heise, Stephan J.; Richter, Michael; Gerliz, V.; Hammer, Maria S.; Ohland, J.; Hammer-Riedel, Ingo

doi:10.1016/j.tsf.2016.08.035

Cited by 10 publications

(6 citation statements)

References 7 publications

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“…In contrast, more complex kinetic models have been developed that incorporate the effects of carrier trapping/detrapping processes at defect states close to the conduction band, 32,33 including some that consider energetic and/or spatial distributions of defect states. 37,41 These models suggest that the long decay time observed by TRPL can either be attributed to SRH recombination (as in the simple picture described above) or by the characteristic time for the SRH recombination process modified by electron capture and release from the defect states, τ decay = (τ e /τ c ) × τ SRH . In the latter case, the estimated carrier capture (τ c ) and emission (τ e ) times for the ca.…”

Section: Discussion Of Carrier Dynamicsmentioning

confidence: 96%

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

Ferguson

Farshchi²,

Paul

et al. 2020

Journal of Applied Physics

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Using a combination of optical and electrical measurements, we develop a model for metastable defects in Ag-alloyed Cu(In,Ga)Se 2 , 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)Se 2 absorbers and subsequently exposing them to various stresses (light soaking and dark-heat), we explore 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 E v + 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.

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Section: Discussion Of Carrier Dynamicsmentioning

confidence: 96%

“…15.4 ± 3.3 ns (Initial) and 40 ± 10 ns (DH1000). Using the range of published electron capture cross sections of CIGS (1.0−50 × 10 −14 cm 2 ), 31,37,40,41 we estimate the density of SRH recombination centers to be in the ranges ca. (0.03−1.5) × 10 14 cm −3 (Initial) and ca.…”

Section: Discussion Of Carrier Dynamicsmentioning

confidence: 99%

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

Ferguson

Farshchi²,

Paul

et al. 2020

Journal of Applied Physics

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“…Recently, trapping of minority carriers has also been proposed to influence the measured decay tail time 25–27 , which was mainly motivated by a strong temperature dependence of the decay tail time 26 . While trapping was included into the model presented in 27 , no temperature dependent transients were measured. Redinger et al .…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Bulk and surface recombination properties in thin film semiconductors with different surface treatments from time-resolved photoluminescence measurements

Weiss

Bissig

Feurer

et al. 2019

Sci Rep

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The knowledge of minority carrier lifetime of a semiconductor is important for the assessment of its quality and design of electronic devices. Time-resolved photoluminescence (TRPL) measurements offer the possibility to extract effective lifetimes in the nanosecond range. However, it is difficult to discriminate between surface and bulk recombination and consequently the bulk properties of the semiconductor cannot be estimated reliably. Here we present an approach to constrain systematically the bulk and surface recombination parameters in semiconducting layers and reduces to finding the roots of a mathematical function. This method disentangles the bulk and surface recombination based on TRPL decay times of samples with different surface preparations. The technique is exemplarily applied to a CuInSe 2 and a back-graded Cu(In,Ga)Se 2 compound semiconductor, and upper and lower bounds for the recombination parameters and the mobility are obtained. Sets of calculated parameters are extracted and used as input for simulations of photoluminescence transients, yielding a good match to experimental data and validating the effectiveness of the methodology. A script for the simulation of TRPL transients is provided.

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“…However, experimental evidence has been presented that trapping of minority charge carriers may impact these measured lifetimes, which results in measured effective lifetimes larger than the bulk lifetime [6,7]. These trapping states are incorporated into several simulation models presented in literature to describe experimental data [8,9]. The main experimental evidence for trapping is a temperature dependence of the measured photoluminescence (PL) decay times, which cannot be explained by the temperature dependence of Shockley-Read-Hall (SRH) recombination [7].…”

Section: Introductionmentioning

confidence: 99%

Time-resolved photoluminescence on double graded Cu(In,Ga)Se₂ – Impact of front surface recombination and its temperature dependence

Weiss

Carron

Wolter

et al. 2019

Science and Technology of Advanced Materials

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Time-resolved photoluminescence (TRPL) is applied to determine an effective lifetime of minority charge carriers in semiconductors. Such effective lifetimes include recombination channels in the bulk as well as at the surfaces and interfaces of the device. In the case of Cu(In,Ga)Se 2 absorbers used for solar cell applications, trapping of minority carriers has also been reported to impact the effective minority carrier lifetime. Trapping can be indicated by an increased temperature dependence of the experimentally determined photoluminescence decay time when compared to the temperature dependence of Shockley-Read-Hall (SRH) recombination alone and can lead to an overestimation of the minority carrier lifetime. Here, it is shown by technology computer-aided design (TCAD) simulations and by experiment that the intentional double-graded bandgap profile of high efficiency Cu(In,Ga)Se 2 absorbers causes a temperature dependence of the PL decay time similar to trapping in case of a recombinative front surface. It is demonstrated that a passivated front surface results in a temperature dependence of the decay time that can be explained without minority carrier trapping and thus enables the assessment of the absorber quality by means of the minority carrier lifetime. Comparison with the absolute PL yield and the quasi-Fermi-level splitting (QFLS) corroborate the conclusion that the measured decay time corresponds to the bulk minority carrier lifetime of 250 ns for the double-graded CIGS absorber under investigation. ARTICLE HISTORY

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Simulation of metastable changes in time resolved photoluminescence of Cu(In,Ga)Se2 thin film solar cells upon light soaking treatment

Cited by 10 publications

References 7 publications

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

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

Bulk and surface recombination properties in thin film semiconductors with different surface treatments from time-resolved photoluminescence measurements

Time-resolved photoluminescence on double graded Cu(In,Ga)Se₂ – Impact of front surface recombination and its temperature dependence

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Simulation of metastable changes in time resolved photoluminescence of Cu(In,Ga)Se2 thin film solar cells upon light soaking treatment

Cited by 10 publications

References 7 publications

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

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

Bulk and surface recombination properties in thin film semiconductors with different surface treatments from time-resolved photoluminescence measurements

Time-resolved photoluminescence on double graded Cu(In,Ga)Se2 – Impact of front surface recombination and its temperature dependence

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Time-resolved photoluminescence on double graded Cu(In,Ga)Se₂ – Impact of front surface recombination and its temperature dependence