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Book Nanoscale Measurements of the Surface Photovoltage in Cu In Ga Se2 Cu2ZnSn4 and Cu2ZnSnSe4 Thin Films

Download or read book Nanoscale Measurements of the Surface Photovoltage in Cu In Ga Se2 Cu2ZnSn4 and Cu2ZnSnSe4 Thin Films written by and published by . This book was released on 2011 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report on recent advances in the development of nanoscale measurements of the surface photovoltage (SPV) based on scanning tunneling microscopy (STM) and its application to the kesterites Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe). One critical aspect of the electronic structure of Cu(In, Ga)Se2 (CIGS) that has yet to be determined in their related kesterite compounds is the character of the surface electronics. In CIGS, spontaneous deviations in the stoichiometry of the surface cause a depletion (or even a type inversion) region that reinforces the CIGS homojunction. First-principle calculations predict that this inversion region will be more difficult to form in CZTS. In this contribution, the characteristics of the surface space charge region for both CIGS and CZTS(e) are investigated by STM. The implications of the results of these measurements on the future development of CZTS solar cells will be discussed.

Book AFM Based Microelectrical Characterization of Grain Boundaries in Cu In Ga Se2 Thin Films

Download or read book AFM Based Microelectrical Characterization of Grain Boundaries in Cu In Ga Se2 Thin Films written by R. Noufi and published by . This book was released on 2005 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report on a direct measurement of two-dimensional potential distribution on the surface of Cu(In, Ga)Se2 thin films using a nanoscale electrical characterization of scanning Kelvin probe microscopy both in air and in ultra-high vacuum. The potential measurement reveals a higher surface potential or a smaller work function on grain boundaries (GBs) of the film than on the grain surfaces. This demonstrates the existence of a local built-in potential on GBs, and the GB is positively charged. The role of the built-in potential in device performance was further examined and found to be positive, by tuning Ga content or bandgap of the film. With increasing Ga content, the potential drops sharply in a Ga range of 28%-38%. Comparing the change in the built-in potential to the theoretical and experimental photoconversion efficiencies, we conclude that the potential plays a significant role in the device conversion efficiency of NREL's three-stage Cu(In, Ga)Se2 device.

Book Local Built in Potential on Grain Boundary of Cu In Ga Se2 Thin Films

Download or read book Local Built in Potential on Grain Boundary of Cu In Ga Se2 Thin Films written by R. Noufi and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report on a direct measurement of two-dimensional potential distribution on the surface of Cu(In, Ga)Se2 (CIGS) thin films using a nanoscale electrical characterization of scanning Kelvin probe microscopy (SKPM). The potential measurement reveals a higher surface potential or a smaller work function on grain boundaries (GBs) of the film than on the grain surfaces. This demonstrates the existence of a local built-in potential on GBs and that the GB is positively charged. The role of the built-in potential in device performance was further examined by tuning Ga content or band gap of the film. With increasing Ga content, the GB potential drops sharply in a Ga range of 28%-38%. Comparing the change in the built-in potential to the theoretical and experimental photoconversion efficiencies, we conclude that the potential plays a significant role in the device conversion efficiency of NREL's three-stage CIGS device.

Book Growth of Cu In Ga Se 1tn2 Thin Films

Download or read book Growth of Cu In Ga Se 1tn2 Thin Films written by Thomas Schlenker and published by . This book was released on 2005 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Microstructure of Surface Layers in Cu In Ga Se2 Thin Films

Download or read book Microstructure of Surface Layers in Cu In Ga Se2 Thin Films written by and published by . This book was released on 2003 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: In most Cu(In, Ga)Se2 thin films used for solar cells, there usually exist interfaces lying about 0.1 to 0.2 m below the surfaces. We report on a convergent-beam electron diffraction and energy-dispersive X-ray spectroscopy study of the microstructure and chemical composition of the surface region in Cu(In, Ga)Se2 thin films. We find that the surface region and the bulk are structurally similar, with no ordered defect chalcopyrite structure observed. However, their composition is slightly different, indicating that they can have different point-defect physics. Our results suggest that the subinterfaces and the bulk absorber may form homojunctions.

Book Depth resolved Band Gap in Cu In Ga S Se 2 Thin Films

Download or read book Depth resolved Band Gap in Cu In Ga S Se 2 Thin Films written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The surface composition of Cu(In, Ga)(S, Se)2 (?CIGSSe?) thin films intrinsically deviates from the corresponding bulk composition, which also modifies the electronic structure and thus the optical properties. We have used a combination of photon and electron spectroscopies with different information depths to gain depth-resolved information on the band gap energy (Eg) in CIG(S)Se thin films. We find an increasing Eg with decreasing information depth, indicating the formation of a surface region with significantly higher Eg. This Eg-widened surface region extends further into the bulk of the sulfur-free CIGSe thin film compared to the CIGSSe thin film.

Book Cu In Ga Se2 Thin Film Evolution During Growth A Photoluminescence Study Preprint

Download or read book Cu In Ga Se2 Thin Film Evolution During Growth A Photoluminescence Study Preprint written by and published by . This book was released on 2002 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This conference paper describes the in-depth understanding of the defect formation and resulting changes in material quality occurring during the Cu(In,Ga)Se2 growth process is vital to the successful and widespread use of this photovoltaic material. In an attempt to develop such an understanding, we investigated the growth of Cu(In,Ga)Se2 thin-films from (In,Ga)2Se3 precursors. This was achievedby using energy- and time-resolved photoluminescence spectroscopies to characterize a series of thin-films, each removed at a different point along the reaction pathway of the 'three-stage' growth process. The resulting thin-films are representative of the absorber layer as it proceeds from a Cu-rich to In(Ga)-rich state. The experimental results support a growth model incorporating defectchanges in the dominant defect states and improvement in the recombination lifetime during this final stage of the growth process as the material transitions to a Cu-poor phase.

Book Determination of Grain Boundary Charging in Cu In Ga Se2 Thin Films

Download or read book Determination of Grain Boundary Charging in Cu In Ga Se2 Thin Films written by and published by . This book was released on 2012 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface potential mapping of Cu(In, Ga)Se2 (CIGS) thin films using scanning Kelvin probe force microscopy (SKPFM) aims to understand the minority-carrier recombination at the grain boundaries (GBs) of this polycrystalline material by examining GB charging, which has resulted in a number of publications. However, the reported results are highly inconsistent. In this paper, we report on the potential mapping by measuring wide-bandgap or high-Ga-content films and by using a complementary atomic force microscopy-based electrical technique of scanning capacitance microscopy (SCM). The results demonstrate consistent, positively charged GBs on our high-quality films with minimal surface defects/charges.

Book Investigation of the Microstructure of Cu In Ga Se2 Thin Films Used in High Efficiency Devices

Download or read book Investigation of the Microstructure of Cu In Ga Se2 Thin Films Used in High Efficiency Devices written by and published by . This book was released on 2002 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: This conference paper describes the microstructure of Cu(In, Ga)Se2 (CIGS) films, as it transitioned from Cu-rich to In-rich composition, by transmission electron microscopy, and energy-dispersive X-ray spectroscopy. We find that the Cu-rich samples have larger grains than the In-rich samples, and they contain two structurally different forms of the CuxSe secondary phase. These samples also show sub-interfaces about 0.2 .mu.m below the surface. The In-rich samples were almost void of these sub-interfaces.

Book Deposition of Single phase Cu In Ga Se2 Thin Films

Download or read book Deposition of Single phase Cu In Ga Se2 Thin Films written by Buyisiwe M. Mhlungu and published by . This book was released on 2004 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: