Spectroscopic investigation of the deeply buried Cu In,Ga S,Se 2 Mo interface in thin film solar cells

The Cu In,Ga S,Se 2 Mo interface in thin film solar cells has been investigated by surface sensitive photoelectron spectroscopy, bulk sensitive X ray emission spectroscopy, and atomic force microscopy. It is possible to access this deeply buried interface by using a suitable lift off technique, which allows to investigate the back side of the absorber layer as well as the front side of the Mo back contact. We find a layer of Mo S,Se 2 on the surface of the Mo back contact and a copper poor stoichiometry at the back side of the Cu In,Ga S,Se 2 absorber. Furthermore, we observe that the Na content at the Cu In,Ga S,Se 2 Mo interface as well as at the inner grain boundaries in the back contact region is significantly lower than at the absorber front surfac

Comprehensive Comparison of Various Techniques for the Analysis of Elemental Distributions in Thin Films

The present work shows results on elemental distribution analyses in Cu(In,Ga)Se2 thin films for solar cells performed by use of wavelength-dispersive and energy-dispersive X-ray spectrometry (EDX) in a scanning electron microscope, EDX in a transmission electron microscope, X-ray photoelectron, angle-dependent soft X-ray emission, secondary ion-mass (SIMS), time-of-flight SIMS, sputtered neutral mass, glow-discharge optical emission and glow-discharge mass, Auger electron, and Rutherford backscattering spectrometry, by use of scanning Auger electron microscopy, Raman depth profiling, and Raman mapping, as well as by use of elastic recoil detection analysis, grazing-incidence X-ray and electron backscatter diffraction, and grazing-incidence X-ray fluorescence analysis. The Cu(In,Ga)Se2 thin films used for the present comparison were produced during the same identical deposition run and exhibit thicknesses of about 2 μm. The analysis techniques were compared with respect to their spatial and depth resolutions, measuring speeds, availabilities, and detection limit

Synchrotron based spectroscopy for the characterization of surfaces and interfaces in chalcopyrite solar cells

In this paper we describe synchrotron based state of the art spectroscopic methods for the analysis of surfaces and interfaces in thin film photovoltaic devices, their merits and their limitations. Using results obtained with the CISSY end station at the BESSY synchrotron in Berlin, Germany, we show how surface sensitive Synchrotron excited X ray Photoelectron Spectroscopy SXPS and Soft X ray Emission Spectroscopy SXES , which yields compositional and chemical depth information in the tens to hundred nm scale, have increased our knowledge of the chemistry of surfaces and buried interfaces of these system

Cd2 NH3 treatment induced formation of a CdSe surface Layer on CuGaSe2 thin film solar cell absorbers

CuGaSe2 CGSe based high gap thin film solar cells have to date not reached their potential level of electrical performance. In order to elucidate possible shortcomings of the electronic interface structure, we have studied the initial stage of the CdS CGSe interface formation by use of a simple Cd2 NH3 treatment. As in the case of low gap chalcopyrites, we find a Cd containing surface layer, in the present case comprised of approx. one monolayer of CdSe. The results indicate that the CdS CGSe interface is not abrupt, but contains intermediate layers. Furthermore, they shed light on possible surface modification schemes to enhance the overall performance of high gap CGSe chalcopyrite solar cell