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 limits.

Employing r.f. (radiofrequency) magnetron sputtering, molybdenum thin films were fabricated on soda-lime glass substrates for use in Cu(In,Ga)Se2 based solar cells. The physical, electrical and structural properties of the films were studied as a function of two deposition parameters: argon pressure and r.f. power. The strain reversal from tensile to compressive occurs at high pressure and is found to decrease with increasing applied r.f. power. The grain sizes of films deduced from x-ray diffraction measurements (full width at half-maximum), and consistent with atomic force microscope images, increase with increasing argon pressure and power. The resistivity of the films was found to increase with increasing argon pressure and decrease with increasing r.f. power.

Spectroscopic ellipsometry (SE) was used to characterize the conventional back contact layer (Mo) as well as a novel top window layer (In2S3) for use in chalcopyrite photovoltaics technology. For the Mo back contact, in‐situ SE measurements of thin films magnetron sputtered onto glass enabled determination of ε at different thicknesses during growth. The observed strong variations could be understood on the basis of a Drude relaxation time that varies with the Mo film thickness. For the In2S3 window layer, ex‐situ SE measurements showed critical point structures at 2.77±0.08 eV, 4.92±0.005 eV, and 5.64 ± 0.005 eV, as well as an absorption tail with an onset near 1.9 eV. A comparison of the solar cell performance in simulations using either In2S3 or conventional CdS revealed similar quantum efficiencies irrespective of the selected window layer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on pulsed laser deposition of graphite onto flexible plastic and conductive glass substrates for use as a counter electrode in dye-sensitized solar cells. The efficiency of as-prepared graphite electrodes was tested using CdS-sensitized solar cell architecture resulting in external quantum efficiency comparable to that of conventional platinum counter electrodes. This work highlights the possibility of using pulsed laser deposited graphite as a low-cost alternative to platinum, which could be fabricated both on flexible and rigid substrates.

Molybdenum thin films were deposited by rf and dc magnetron sputtering and their properties analyzed with regards to their potential application as a back contact for CIGS solar cells. It is shown that both types of films tend to transition from tensile to compressive strain when the deposition pressure increases, while the conductivity and the grain size decreas. The nucleation of the films characterized byin situand real time spectroscopic ellipsometry shows that both films follow a Volmer-Weber growth, with a higher surface roughness and lower deposition rate for the rf deposited films. The electronic relaxation time was then extracted as a function of bulk layer thickness for rf and dc films by fitting each dielectric function to a Drude free-electron model combined with a broad Lorentz oscillator. The values were fitted to a conical growth mode and demonstrated that the rf-deposited films have already smaller grains than the dc films when the bulk layer thickness is 30 nm.