Is the Cu/Zn Disorder the Main Culprit for the Voltage Deficit in Kesterite Solar Cells?

Bourdais, S.; Choné, Christophe; Delatouche, Bruno; Jacob, Alain; Larramona, Gerardo; Moisan, Camille; Lafond, A.; Donatini, Fabrice; Rey, Germain; Siebentritt, Susanne; Walsh, Aron; Dennler, Gilles

doi:10.1002/aenm.201502276

Cited by 314 publications

(260 citation statements)

References 123 publications

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“…Cu 2 ZnSnS 4 has a similar Urbach energy and has a V OC 0.5 V below its Shockley-Queisser limit value. [46,50] Band tails and sub-bandgap states present in the NiO x ( Figure S43, Supporting Information) and ZnO layers (measured previously, [45,51] and from Figure S42, Supporting Information) can also lead to V OC losses due to carrier thermalization or recombination from the band tails. [45,52] Further device modeling and temperature-dependent V OC measurements are required to quantify the magnitudes of these different effects.…”

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confidence: 69%

“…Disorder in the BiOI absorber could lead to V OC losses, for example due to potential fluctuations in the bandgap. [50] Using photothermal deflection spectroscopy, we measured the Urbach energy to be 70 meV for BiOI grown on quartz, and 90 meV for BiOI grown on NiO x on quartz ( Figure S43, Supporting Information). Cu 2 ZnSnS 4 has a similar Urbach energy and has a V OC 0.5 V below its Shockley-Queisser limit value.…”

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confidence: 99%

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Strongly Enhanced Photovoltaic Performance and Defect Physics of Air‐Stable Bismuth Oxyiodide (BiOI)

et al. 2017

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Bismuth‐based compounds have recently gained increasing attention as potentially nontoxic and defect‐tolerant solar absorbers. However, many of the new materials recently investigated show limited photovoltaic performance. Herein, one such compound is explored in detail through theory and experiment: bismuth oxyiodide (BiOI). BiOI thin films are grown by chemical vapor transport and found to maintain the same tetragonal phase in ambient air for at least 197 d. The computations suggest BiOI to be tolerant to antisite and vacancy defects. All‐inorganic solar cells (ITO|NiOx|BiOI|ZnO|Al) with negligible hysteresis and up to 80% external quantum efficiency under select monochromatic excitation are demonstrated. The short‐circuit current densities and power conversion efficiencies under AM 1.5G illumination are nearly double those of previously reported BiOI solar cells, as well as other bismuth halide and chalcohalide photovoltaics recently explored by many groups. Through a detailed loss analysis using optical characterization, photoemission spectroscopy, and device modeling, direction for future improvements in efficiency is provided. This work demonstrates that BiOI, previously considered to be a poor photocatalyst, is promising for photovoltaics.

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confidence: 69%

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confidence: 99%

Strongly Enhanced Photovoltaic Performance and Defect Physics of Air‐Stable Bismuth Oxyiodide (BiOI)

et al. 2017

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“…Bourdais & al. 40 have shown that CZTSSe samples can have a Cu/Zn disorder ranging from 20% to 100% at room temperature. They demonstrate as well that Cu/Zn disorder does not have an impact on solar cell efficiency in this range of values.…”

Section: Occurrence Quantification In Literaturementioning

confidence: 99%

“…It is worth noticing that both causes cannot be considered at the same level. While band tails (due to electrostatic potential fluctuations or bandgap fluctuations) are directly linked to structural defects in the material (presence of secondary phases in the bulk of the material 12 , Cu/Zn disorder 39 , locally inhomogeneous distribution of the anion 40 , high level of compensated defects 38 ), short minority carrier lifetime might be considered as a potential consequence of similar defects. Shockley-Read-Hall (SRH) recombination on point defects in the bulk of the absorber is generally said to be responsible for this short lifetime 42 but the influence of band tails, grain boundaries or even interfaces on lifetime is rarely discussed 13 .…”

Section: Mapping Of Fundamental Failures In Cd-free Kesterite Solar Cmentioning

confidence: 99%

Analysis of Failure Modes in Kesterite Solar Cells

Grenet

Suzon

Emieux

et al. 2018

ACS Appl. Energy Mater.

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An intense research activity has been carried out in the past few years to improve efficiencies and understand limitations in kesterite based solar cells. Despite notable efforts to determine and list the different failure modes affecting the photovoltaic properties of these devices, very few works try to quantify and classify the effect of these failure modes. In this study, an exhaustive literature review has first been conducted to determine the different causes leading to limited efficiencies in kesterite devices with an additional focus on cadmium free and critical raw material free devices. Second, an original approach has been employed to quantify the impact of these failure modes on solar cells with the evaluation of feedbacks from 18 scientific experts working on kesterite technology. The result of this survey is analyzed, which allow to determine what should be the research priority for the community to improve efficiencies and drive kesterite technology to the market.

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“…[2] Alkali treatment of kesterite solar cells is one of the measures to reduce the high V OC -deficit and most of today's >10% efficiency kesterite devices utilize the beneficial effects of alkali elements on absorber layer morphology and optoelectronic properties. So far the most research attention has been paid to sodium, resulting in many thorough investigations which revealed grain size enhancement, passivation of grain boundaries, and an increase in net hole concentration as the major beneficial effects of sodium treatments.…”

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confidence: 99%

Complex Interplay between Absorber Composition and Alkali Doping in High‐Efficiency Kesterite Solar Cells

Haass

Andrés

Figi

et al. 2017

Advanced Energy Materials

108

107

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kesterite material with its optimal bandgap and absorption coefficient. [2] Alkali treatment of kesterite solar cells is one of the measures to reduce the high V OC -deficit and most of today's >10% efficiency kesterite devices utilize the beneficial effects of alkali elements on absorber layer morphology and optoelectronic properties. So far the most research attention has been paid to sodium, resulting in many thorough investigations which revealed grain size enhancement, passivation of grain boundaries, and an increase in net hole concentration as the major beneficial effects of sodium treatments. [3][4][5][6] Also lithium addition has shown to improve device performance by boosting the electronic quality of the CZTSSe absorber material and grain boundaries. [7] First studies on the effect of potassium addition confirmed advantageous effects on kesterite absorber growth and optoelectronic properties similar to Na. [8,9] Several studies comparing different alkali elements and their effect on solar cell properties and device performance have recently been published. [10][11][12][13] Table 1 compares the effects on device performance by extracting a ranking of the various alkali elements in each publication in the order of their capability to improve device performance. It is apparent from these rankings that no consistent experimental results have been obtained, which triggers two questions: (i) Why do the published results differ so much? (ii) Which alkali element possesses the highest potential for efficiency improvements?This paper aims to unveil the discrepancy between the recently published results comparing the effects of alkali treatments on device performance. Our hypothesis is that each alkali element requires a different absorber composition to achieve the highest PV performance and we therefore prepared a comprehensive set of samples with different alkali elements and alkali concentrations as well as various metal ratios. All samples were thoroughly characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma-mass spectrometry (ICP-MS), as well as current-voltage (J-V), capacitance-voltage (C-V), time-resolved photoluminescence (TRPL), and external quantum efficiency (EQE) measurements.The methodology used for absorber synthesis is based on the solution process described elsewhere, [14] allowing for accurate alkali incorporation by simply adding alkali chlorides to the solution. [15] Figure 1a illustrates the matrix of sample compositions prepared with five different alkali elements: lithium (Li), Sodium treatment of kesterite layers is a widely used and efficient method to boost solar cell efficiency. However, first experiments employing other alkali elements cause confusion as reported results contradict each other. In this comprehensive investigation, the effects of absorber composition, alkali element, and concentration on optoelectronic properties and device performance are investigated. Experimental results show that in the r...

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Is the Cu/Zn Disorder the Main Culprit for the Voltage Deficit in Kesterite Solar Cells?

Abstract: International audienc

Cited by 314 publications

References 123 publications

Strongly Enhanced Photovoltaic Performance and Defect Physics of Air‐Stable Bismuth Oxyiodide (BiOI)

Strongly Enhanced Photovoltaic Performance and Defect Physics of Air‐Stable Bismuth Oxyiodide (BiOI)

Analysis of Failure Modes in Kesterite Solar Cells

Complex Interplay between Absorber Composition and Alkali Doping in High‐Efficiency Kesterite Solar Cells

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