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• Seed layer deployment clearly improved performance of TiO 2 /Sb 2 Se 3 solar cells. • Pole figures revealed seed layer enhanced texture of Sb 2 Se 3 along [001] direction. • Temperature-dependent admittance spectroscopy detected deep defect at 0.39 eV. • Capacitance-voltage profiles show the defect density could be as high as 1017 cm−3. The performance of a superstrate TiO 2 /Sb 2 Se 3 solar cell, fabricated by close-spaced sublimation technique (CSS), was improved after the deployment of a seed layer. The seed layer caused columnar Sb 2 Se 3 film growth with texture coefficient analysis (TC) showing increased presence of crystal planes, which are inclined towards the [001] crystal direction. Given the highly anisotropic properties of Sb 2 Se 3, preferential growth of (Sb 4 Se 6) n ribbons along the [001] direction is best suited for effective charge collection. Hence, grain orientation of Sb 2 Se 3 films was studied more closely via measurement of pole figures by XRD and orientation distribution maps by electron backscatter diffraction (EBSD). Although the measurements did not reveal strong preferred orientation, it was observed that the columnar Sb 2 Se 3 growth enhanced texture along the [001] direction. Temperature-dependent admittance spectroscopy (TAS) and capacitance–voltage (CV) profiling were performed on the seed-assisted TiO 2 /Sb 2 Se 3 solar cell to evaluate carrier density and deep defects in the Sb 2 Se 3 absorber. TAS study revealed a deep defect with activation energy of 0.39 eV. CV profiles indicated that the density of defects could be as high as 1017 cm−3, which needs to be addressed by post-deposition treatments. [ABSTRACT FROM AUTHOR]

The continuous improvement of Cu(In,Ga)Se 2 (CIGSe) solar cells relies considerably on advanced characterization of individual layers in the solar-cell stacks as well as of completed CIGSe devices. The present contribution provides an overview of corresponding efforts performed by various research groups at Helmholtz-Zentrum Berlin für Materialien und Energie GmbH. In-situ growth monitoring of CIGSe absorber layers by means of energy-dispersive X-ray spectrometry and light scattering is described, as well as structural analyses by means of X-ray and neutron diffraction. In addition, the characterization of surfaces and interfaces by soft X-ray and electron spectroscopy, the microscopic analysis by means of correlative electron microscopy, and optoelectronic characterization by optical spectroscopy are highlighted. The present contribution shows which substantial efforts in a research network are necessary in order to obtain deeper insight into materials properties and potentially limiting factors for the device performance, as well as to be able to control these factors during the solar-cell production. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nondestructive chemical quantitative analysis of Cu(In,Ga)Se2 by photoluminescence. [•] Extension to nondestructive Ga depth profile assessment with confocal measurements. [•] Correlation with Raman scattering microcrystalline and phase assessment. [•] Demonstration of methodologies for monitoring of advanced CIGS PV technologies. [Copyright &y& Elsevier]

Abstract: Thin-film solar cells based on compound semiconductors consist of a multilayer structure with various interfaces and contain a multitude of elements and impurities, etc. A rapid progress of these photovoltaic technologies can only be achieved by an insight-driven optimization/development. Hence it is crucial to characterize and understand the relationship between the chemical and electronic properties of these components. This paper reviews some examples of our recent work characterizing compound semiconductor thin films using laboratory- and synchrotron-based electron and soft X-ray spectroscopic characterization methods. It is demonstrated how these different analytical techniques are extraordinarily powerful to reveal the material characteristics from many different perspectives, ultimately resulting in a comprehensive picture of the related electronic and chemical properties. As examples, the paper will discuss the electronic surface structure of chalcopyrite thin-film solar cell absorbers, the chemical structure of the CdS/chalcopyrite interface, present the band alignment at the CdS/kesterite interface, and report on how post-deposition treatments cause chemical interaction/interdiffusion processes in CdTe/CdS thin-film solar cell structures. [Copyright &y& Elsevier]