Electron-beam-induced current at absorber back surfaces of Cu(In,Ga)Se2 thin-film solar cells

The present review gives an overview of the various reports on properties of line and planar defects in Cu(In,Ga)(S,Se)2 thin films for high‐efficiency solar cells. We report results from various analysis techniques applied to characterize these defects at different length scales, which allow for drawing a consistent picture on structural and electronic defect properties. A key finding is atomic reconstruction detected at line and planar defects, which may be one mechanism to reduce excess charge densities and to relax deep‐defect states from midgap to shallow energy levels. On the other hand, nonradiative Shockley–Read–Hall recombination is still enhanced with respect to defect‐free grain interiors, which is correlated with substantial reduction of luminescence intensities. Comparison of the microscopic electrical properties of planar defects in Cu(In,Ga)(S,Se)2 thin films with two‐dimensional device simulations suggest that these defects are one origin of the reduced open‐circuit voltage of the photovoltaic devices. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

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“…Experimental details of these measurements are given in Ref. , and results obtained on CuInSe 2 , and Cu(In,Ga)Se 2 are shown in Figs. and .…”

Section: Impact Of Extended Structural Defects On Short‐circuit Currementioning

confidence: 99%

Compositional and electrical properties of line and planar defects in Cu(In,Ga)Se₂ thin films for solar cells – a review

Abou‐Ras

Schmidt

Schäfer

et al. 2016

Physica Rapid Research Ltrs

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“…28,32,33 Decreases are found to be as large as 30-50 rel.%, while the luminescence maxima exhibit shifts only a few meV. An example of combined EBSD and CL acquisitions at identical positions is shown in Fig.…”

Section: Ebsd Combined With Other Scanning Microscopy Techniquesmentioning

confidence: 96%

Electron Backscatter Diffraction: An Important Tool for Analyses of Structure–Property Relationships in Thin-Film Solar Cells

Abou‐Ras

Kavalakkatt

Nichterwitz

et al. 2013

JOM

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The present work gives an overview of the application of electron backscatter diffraction (EBSD) in the field of thin-film solar cells, which consist of stacks of polycrystalline layers on various rigid or flexible substrates. EBSD provides access to grain-size and local-orientation distributions, film textures, and grain-boundary types. By evaluation of the EBSD patterns within individual grains of the polycrystalline solar cell layers, microstrain distributions also can be obtained. These microstructural properties are of considerable interest for research and development of thin-film solar cells. Moreover, EBSD may be performed three-dimensionally, by alternating slicing of cross sections in a focused ion-beam machine and EBSD acquisition. To relate the microstructural properties to the electrical properties of individual layers as well as to the device performances of corresponding solar cells, EBSD can be combined with electron-beam-induced current and cathodoluminescence measurements and with various scanning-probe microscopy methods such as Kelvin-probe force, scanning spreading resistance, or scanning capacitance microscopy on identical specimen positions. Together with standard device characterization of thin-film solar cells, these scanning microscopy measurements provide the means for extensive analysis of structure-property relationships in solar-cell stacks with polycrystalline layers.

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“…Generally, these losses can be caused by parasitic and incomplete absorption or non‐efficient charge carrier collection . The electron beam induced current technique (EBIC) promises a reliable and simple experimental way to estimate collection losses but it tends to be impeded by effects of surface recombination …”

Section: Introductionmentioning

confidence: 99%

“…Measurements in the limit of high surface recombination have been exploited to estimate cross‐section and grain boundary surface recombination velocities which were found to be on the order of 10 5 and 10 4 cm s −1 , respectively . In this cases reliable and direct extraction of the collection function is complicated and fitting procedures are necessary . The use of thin amorphous atomic layer deposition (ALD) Al 2 O 3 layers on the cross‐section is an attempt to actively reduce the cross‐section surface recombination for measurements with low injection energy and current which are susceptible for surface recombination.…”

Section: Introductionmentioning

confidence: 99%

Surface Passivation for Reliable Measurement of Bulk Electronic Properties of Heterojunction Devices

Bissig

Guerra‐Nuñez

Carron

et al. 2016

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Quantum efficiency measurements of state of the art Cu(In,Ga)Se (CIGS) thin film solar cells reveal current losses in the near infrared spectral region. These losses can be ascribed to inadequate optical absorption or poor collection of photogenerated charge carriers. Insight on the limiting mechanism is crucial for the development of more efficient devices. The electron beam induced current measurement technique applied on device cross-sections promises an experimental access to depth resolved information about the charge carrier collection probability. Here, this technique is used to show that charge carrier collection in CIGS deposited by multistage co-evaporation at low temperature is efficient over the optically active region and collection losses are minor as compared to the optical ones. Implications on the favorable absorber design are discussed. Furthermore, it is observed that the measurement is strongly affected by cross-section surface recombination and an accurate determination of the collection efficiency is not possible. Therefore it is proposed and shown that the use of an Al O layer deposited onto the cleaved cross-section significantly improves the accuracy of the measurement by reducing the surface recombination. A model for the passivation mechanism is presented and the passivation concept is extended to other solar cell technologies such as CdTe and Cu (Zn,Sn)(S,Se) .

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Electron-beam-induced current at absorber back surfaces of Cu(In,Ga)Se2 thin-film solar cells

Cited by 25 publications

References 33 publications

Compositional and electrical properties of line and planar defects in Cu(In,Ga)Se₂ thin films for solar cells – a review

Compositional and electrical properties of line and planar defects in Cu(In,Ga)Se₂ thin films for solar cells – a review

Electron Backscatter Diffraction: An Important Tool for Analyses of Structure–Property Relationships in Thin-Film Solar Cells

Surface Passivation for Reliable Measurement of Bulk Electronic Properties of Heterojunction Devices

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Electron-beam-induced current at absorber back surfaces of Cu(In,Ga)Se2 thin-film solar cells

Cited by 25 publications

References 33 publications

Compositional and electrical properties of line and planar defects in Cu(In,Ga)Se2 thin films for solar cells – a review

Compositional and electrical properties of line and planar defects in Cu(In,Ga)Se2 thin films for solar cells – a review

Electron Backscatter Diffraction: An Important Tool for Analyses of Structure–Property Relationships in Thin-Film Solar Cells

Surface Passivation for Reliable Measurement of Bulk Electronic Properties of Heterojunction Devices

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Product

Resources

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Compositional and electrical properties of line and planar defects in Cu(In,Ga)Se₂ thin films for solar cells – a review

Compositional and electrical properties of line and planar defects in Cu(In,Ga)Se₂ thin films for solar cells – a review