Influence of different sulfur to selenium ratios on the structural and electronic properties of Cu(In,Ga)(S,Se)2 thin films and solar cells formed by the stacked elemental layer process

Abstract

Investigation of combinatorial coevaporated thin film Cu2ZnSnS4. I. Temperature effect, crystalline phases, morphology, and photoluminescence Toward a high Cu2ZnSnS4 solar cell efficiency processed by spray pyrolysis method J. Renewable Sustainable Energy 5, 053137 (2013); 10.1063/1.4825253Analysis of S -rich CuIn ( S , Se ) 2 layers for photovoltaic applications: Influence of the sulfurization temperature on the crystalline properties of electrodeposited and sulfurized CuInSe 2 precursorsIn this study, we investigate the effect of different elemental selenium to elemental sulfur ratios on the chalcopyrite phase formation in Cu(In,Ga)(S,Se) 2 thin films. The films are formed by the stacked elemental layer process. The structural and electronic properties of the thin films and solar cells are analyzed by means of scanning electron microscopy, glow discharge optical emission spectrometry, X-ray diffraction, X-ray fluorescence, Raman spectroscopy, spectral photoluminescence as well as current-voltage, and quantum efficiency measurements. The influence of different S/(SþSe) ratios on the anion incorporation and on the Ga/In distribution is investigated. We find a homogenous sulfur concentration profile inside the film from the top surface to the bottom. External quantum efficiency measurements show that the band edge of the solar cell device is shifted to shorter wavelength, which enhances the open-circuit voltages. The relative increase of the open-circuit voltage with S/(SþSe) ratio is lower than expected from the band gap energy trend, which is attributed to the presence of S-induced defects. We also observe a linear decrease of the short-circuit current density with increasing S/(SþSe) ratio which can be explained by a reduced absorption. Above a critical S/(SþSe) ratio of around 0.61, the fill factor drops drastically, which is accompanied by a strong series resistance increase which may be attributed to changes in the back contact or p-n junction properties. V C 2014 AIP Publishing LLC.

Advanced characterization of electrodeposition-based high efficiency solar cells: Non-destructive Raman scattering quantitative assessment of the anion chemical composition in Cu(In,Ga)(S,Se)2 absorbers

“…Furthermore, the spike reduction would explain the lower decrease of the short circuit current compared to the expected one as well as the observed band gap and Fill Factor increases in these devices. Similar effects related to the presence of S at the surface region of the absorber layers have also been reported for CIGS devices fabricated with different processes [5] to [8].…”

“…A key feature in these processes is the controlled combination of sulfur and gallium to obtain the desired band-gap profile with high homogeneity of all elements over the full module area [5][6][7][8][9]. This work reports a detailed optoelectronic characterization of S-free (CIGSe:CuInGaSe 2 ) and S-containing (CIGSSe) electrodeposition-based solar cells, showing the impact of sulfur incorporation on devices characteristics.…”

Germanium Incorporation in Cu2ZnSnS4 and Formation of a Sn–Ge Gradient

“…Cu(In,Ga)(S,Se 2 ) (CIGS) solar cells have improved steadily up to the current record efficiency of 23.3% . Some of the important contributing factors to the success of CIGS solar cells are the possibility of bandgap profiling with In/Ga or S/Se compositional gradients and low density of detrimental bulk defects . CZTSSe is still limited to a reported efficiency of 12.6% even though several groups have recently reached 11–12% efficiency using different fabrication routes .…”

Influence of Mo–N as diffusion barrier in Mo back contacts for Cu(In,Ga)Se2 solar cells

“…Via magnetron sputtering 500 nm Mo back contact is deposited on the glass using the conditions stated in [13]. The Mo back contact consists of a 100 nm seed layer which is sputtered at higher pressure (p≈10 −3 mbar) and a 400 nm good conducting layer which is sputtered at lower pressure (p ≈ 10 − 4 mbar).…”

“…The N 2 /Ar ratio is changed continously from 0/200 sccm (normal Mo sputtering conditions) to 200/0 sccm (normal Mo-N sputtering conditions) during 10 s. This should lead to a better adhesion and functionality of the Mo-N on Mo layer. The CIGSe thin film is processed via direct current sputtering (p ≈ 10 −3 mbar) of CuGa alloy target and In elemental target [13]. In the next step elemental Se is evaporated (base pressure of p ≈ 10 − 5 mbar) on the pure Mo-N/Mo layer or on the additional metallic precursor layer with a thickness between 0.5 and 1.5 μm.…”