18 research outputs found
In-situ formation of magnesium silicide nanoparticles on the surface of the hydrogenated silicon films
The magnesium silicide nanoparticles were formed on the surface of hydrogenated silicon thin films by thermal evaporation, annealing and hydrogen plasma treatment. The high reactivity of silicon and magnesium leads to the self-formation of magnesium silicide nanoparticles (NPs). The reaction is stimulated in-situ by the low pressure hydrogen plasma. The presence of Mg2Si NPs was confirmed by SEM and Raman spectroscopy. The photothermal deflection spectroscopy (PDS) shows the enhanced optical absorption in the near infrared spectrum. The diode structures with insitu embedded Mg2Si NPs were characterized by the volt-ampere measurements in dark and under AM1.5 spectrum
Single-Source, Solvent-Free, Room Temperature Deposition of Black Îł-CsSnI<sub>3</sub> Films
The presence of a non-optically active polymorph (yellow-phase) competing
with the optically active polymorph (black -phase) at room temperature
in CsSnI3 and the susceptibility of Sn to oxidation, represent two of the
biggest obstacles for the exploitation of CsSnI3 in optoelectronic devices.
Here room-temperature single-source in vacuum deposition of smooth black
- CsSnI3 thin films is reported. This has been done by fabricating a
solid target by completely solvent-free mixing of CsI and SnI2 powders and
isostatic pressing. By controlled laser ablation of the solid target on an
arbitrary substrate at room temperature, the formation of CsSnI3 thin films
with optimal optical properties is demonstrated. The films present a band gap
of 1.32 eV, a sharp absorption edge and near-infrared photoluminescence
emission. These properties and X-ray diffraction of the thin films confirmed
the formation of the orthorhombic (B-) perovskite phase. The thermal
stability of the phase was ensured by applying in situ an Al2O capping
layer. This work demonstrates the potential of pulsed laser deposition as a
volatility-insensitive single-source growth technique of halide perovskites and
represents a critical step forward in the development and future scalability of
inorganic lead-free halide perovskites.Comment: Accepted by Advanced Materials Interfaces, 16 pages, 4 figures, and
supplemen
Enhancing the optoelectronic properties of amorphous zinc tin oxide by subgap defect passivation: A theoretical and experimental demonstration
Study of defects and microstructure of amorphous and microcrystalline silicon thin films and polycrystalline diamond using optical methods
Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi
Study of the surface properties of ZnO nanocolumns used for thin-film solar cells
Densely packed ZnO nanocolumns (NCs), perpendicularly oriented to the fused-silica substrates were directly grown under hydrothermal conditions at 90 °C, with a growth rate of around 0.2 μm/h. The morphology of the nanostructures was visualized and analyzed by scanning electron microscopy (SEM). The surface properties of ZnO NCs and the binding state of present elements were investigated before and after different plasma treatments, typically used in plasma-enhanced CVD solar cell deposition processes, by X-ray photoelectron spectroscopy (XPS). Photothermal deflection spectroscopy (PDS) was used to investigate the optical and photoelectrical characteristics of the ZnO NCs, and the changes induced to the absorptance by the plasma treatments. A strong impact of hydrogen plasma treatment on the free-carrier and defect absorption of ZnO NCs has been directly detected in the PDS spectra. Although oxygen plasma treatment was proven to be more efficient in the surface activation of the ZnO NC, the PDS analysis showed that the plasma treatment left the optical and photoelectrical features of the ZnO NCs intact. Thus, it was proven that the selected oxygen plasma treatment can be of great benefit for the development of thin film solar cells based on ZnO NCs
Electroluminescence of thin film
Hydrogenated amorphous substoichiometric silicon carbon alloys (a-SiC:H) with and without embedded Ge nanoparticles (NPs) have been prepared by plasma enhanced chemical vapour deposition combined with in-situ Ge evaporation and annealing on semi-transparent boron doped nano-crystalline diamond coated Ti grids. The presence of Ge NPs embedded in the amorphous phase has been confirmed by transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses. Current-voltage (I–V) characteristics and near infrared electroluminescence (EL) spectra were measured to compare performance of diodes. The relatively strong EL appears in diodes with integrated Ge NPs near the direct band-gap transition of Ge at about 0.82 eV with an intensity strongly correlating with current density. However, it has also been found that Ge NPs integrated into a-SiC:H significantly deteriorates diode I–V characteristic
Spatial Localization of Defects in Halide Perovskites Using Photothermal Deflection Spectroscopy
Photothermal deflection
spectroscopy (PDS) emerges as a highly
sensitive noncontact technique for measuring absorption spectra and
serves for studying defect states within semiconductor thin films.
In our study, we applied PDS to methylÂammonium lead bromide
single crystals. By analyzing the frequency dependence of the PDS
spectra and the phase difference of the signal, we can differentiate
between surface and bulk deep defect absorption states. This methodology
allowed us to investigate the effects of bismuth doping and light-induced
degradation. The identified absorption states are attributed to MA+ vibrational states and structural defects, and their influence
on the nonradiative recombination probability is discussed. This distinction
significantly enhances our capability to characterize and analyze
perovskite materials at a deeper level
Spatial Localization of Defects in Halide Perovskites Using Photothermal Deflection Spectroscopy
Photothermal deflection
spectroscopy (PDS) emerges as a highly
sensitive noncontact technique for measuring absorption spectra and
serves for studying defect states within semiconductor thin films.
In our study, we applied PDS to methylÂammonium lead bromide
single crystals. By analyzing the frequency dependence of the PDS
spectra and the phase difference of the signal, we can differentiate
between surface and bulk deep defect absorption states. This methodology
allowed us to investigate the effects of bismuth doping and light-induced
degradation. The identified absorption states are attributed to MA+ vibrational states and structural defects, and their influence
on the nonradiative recombination probability is discussed. This distinction
significantly enhances our capability to characterize and analyze
perovskite materials at a deeper level
Photocurrent Spectroscopy of Perovskite Layers and Solar Cells: A Sensitive Probe of Material Degradation
Optical absorptance spectroscopy of polycrystalline CH3NH3PbI3 films usually indicates the presence of a PbI2 phase, either as a preparation residue or due to film degradation, but gives no insight on how this may affect electrical properties. Here, we apply photocurrent spectroscopy to both perovskite solar cells and coplanar-contacted layers at various stages of degradation. In both cases, we find that the presence of a PbI2 phase restricts charge-carrier transport, suggesting that PbI2 encapsulates CH3NH3PbI3 grains. We also find that PbI2 injects holes into the CH3NH3PbI3 grains, increasing the apparent photosensitivity of PbI2. This phenomenon, known as modulation doping, is absent in the photocurrent spectra of solar cells, where holes and electrons have to be collected in pairs. This interpretation provides insights into the photogeneration and carrier transport in dual-phase perovskites