Jaison Kavalakkatt

Defect study of Cu2ZnSn(SxSe1−x)4 thin film absorbers using photoluminescence and modulated surface photovoltage spectroscopy

Defect states in Cu2ZnSn(SxSe1� x)4 thin films with x ¼0.28, 0.36, and 1 were studied by combining photoluminescence (PL) and modulated surface photovoltage (SPV) spectroscopy. A single broad band emission in the PL spectra was observed and can be related to quasi-donor-acceptor pair transitions. The analysis of the temperature dependent quenching of the PL band (x ¼0.28, 0.36, and 1) and SPV (x ¼0.28) signals resulted in activation energies below 150meV for PL and about 90 and 300meV for SPV. Possible intrinsic point defects that might be associated with these observed activation energies are discussed. V C 2015 AIP Publishing LLC.

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

The present work reports on investigations of the influence of the microstructure on electronic properties of Cu(In,Ga)Se2 (CIGSe) thin-film solar cells. For this purpose, ZnO/CdS/CIGSe stacks of these solar cells were lifted off the Mo-coated glass substrates. The exposed CIGSe backsides of these stacks were investigated by means of electron-beam-induced current (EBIC) and cathodoluminescence (CL) measurements as well as by electron backscattered diffraction (EBSD). EBIC and CL profiles across grain boundaries (GBs), which were identified by EBSD, do not show any significant changes at Σ3 GBs. Across non-Σ3 GBs, on the other hand, the CL signals exhibit local minima with varying peak values, while by means of EBIC, decreased and also increased short-circuit current values are measured. Overall, EBIC and CL signals change across non-Σ3 GBs always differently. This complex situation was found in various CIGSe thin films with different [Ga]/([In]+[Ga]) and [Cu]/([In]+[Ga]) ratios. A part of the EBIC profile...

Electron backscatter diffraction: Exploring the microstructure in Cu(In,Ga)(S,Se) 2 and CdTe thin-film solar cells

Electron backscatter diffraction (EBSD) in a scanning electron microscope provides access to grain-size and local-orientation distributions, film textures and grain-boundary types of thin-film solar cells. Since EBSD exhibits an information depth of only about 20 nm in Cu(In,Ga)(S,Se)2 and CdTe thin films, the most important issue of the corresponding analyses is an appropriate preparation of layer or cross-section surfaces in order to reduce possible surface roughnesses to a minimum. When EBSD is combined with energy-dispersive X-ray spectrometry (EDX), electron-beam-induced current (EBIC) and cathodoluminescence (CL) measurements, compositional as well as electrical and optoelectronic material properties are obtained, complementarily to the microstructural information.