This work concerns the interpretation of capacitance spectroscopy results in perovskite-based solar cells. Based on the deep level transient spectroscopy and admittance spectroscopy results, we ...present arguments that the observable signals in perovskite-based solar cells come from anion migration rather than being a response from deep trap energy levels. The ion migration parameters, such as activation energy and ion concentration, are calculated and compared to theoretical values for different migration paths of ions in perovskites. Those parameters evolve with time, reflecting in the degradation of the cells, which we propose to link with a change in the anion migration path in perovskite.
•The same signal is observed in DLTS and admittance spectroscopy.•Its activation energy is in the 0.3 eV–0.5 eV range and decays with time.•Time constants and the presence of large capacitance transients at +1 V point into the diffusion related origin of the signals.•Low activation energy, DLTS sign, comparison with other experiments and theoretical calculations point into anion diffusion.•The observed, dominating signal correlates with the increased shunt of the device.
This work concerns the interpretation of defect spectroscopy signals in CuInSe2-and Cu(In,Ga)Se2-based Schottky junctions and thin films, which are investigated using capacitance- and current-based ...techniques. Two common signals are distinguished. It is shown here that the activation energies and consequently the emission rates vary between the samples and are strongly correlated with the hole concentration in the material. Models that can account for these changes are discussed. Based on deep-level transient spectroscopy and conductivity measurements, we present arguments for the validity of the existing models and discuss the hypothesis that the observable signals may originate from extended defects in Cu(In,Ga)Se2.
•Two signals were distinguished in CIS and CIGS Schottky junctions using capacitance spectroscopy techniques.•The activation energy and emission rates depend on hole concentration.•Signals exhibit logarithmic capture kinetics.•Activation energy of capacitance spectroscopy signals is correlated with activation energy of conductivity.
The aim of this study was to analyse the effect of pomegranate juice (POM) supplementation on the levels of selected pro-inflammatory cytokines, hepcidin and markers of iron metabolism in ...well-trained rowers.
The double-blind placebo-controlled study included 19 members of the Polish Rowing Team. The athletes were randomised into the supplemented group (n = 10), receiving 50 ml of standardised POM daily for two months, or the placebo group (n = 9). The subjects performed a 2000 m test on the rowing ergometer at the start of the project (baseline) and end of follow-up period. Blood samples from the antecubital vein were obtained three times during each trial: prior to the exercise, one minute after the test, and following a 24 h recovery.
The study documented the beneficial effect of supplementation with pomegranate fruit juice on TAC (P < 0.002). During the resting period, TAC level in the supplemented group was significantly higher than in the placebo group (x ± SD, 2.49 ± 0.39 vs. 1.88 ± 0.45, P < 0.05). The ergometric test conducted at baseline demonstrated a significant post-exercise increase in the concentrations of soluble transferrin receptors (P < 0.04), iron (P < 0.002) and IL-6 (P < 0.02), and to a significant post-exercise decrease in TAC. A significant increase in IL-6 concentration was also observed 24 h post-exercise. The exercise test conducted at the end of the follow-up period resulted in a significant decrease in TBIC and a significant increase in UIBC (P < 0.001), observed in both groups, both immediately post-exercise and after the resting period.
Supplementation with POM contributed to a significant strengthening of plasma antioxidant potential in the group of well-trained rowers, but had no effect on iron metabolism markers.
This work contributes to the discussion on defect levels in Cu(In,Ga)Se2 photovoltaic material. CuInSe2- and Cu(In,Ga)Se2- based Schottky junctions, solar cells and thin films were investigated using ...complementary capacitance and current spectroscopic techniques. Depending on the applied technique and type of investigated structure, six different signals were observed. Out of the signals identified, three were ascribed to responses from bulk defects-two electron and one hole trap. The remainder were discussed in light of available in-literature models including carrier mobility freeze-out and non-ohmic back junction.
This work contributes to the discussion on the influence of the back electrode on the capacitance spectroscopy results of Cu(In,Ga)Se2-based solar cells. Devices with Mo and Pt back electrodes were ...investigated by means of admittance spectroscopy and carrier concentration profiling. We present arguments supporting the statement that admittance spectroscopy signals, which are commonly observed and reported, cannot be exclusively attributed to the non-ohmic character of the back electrode.
•Admittance signal may not be necessarily related to the back electrode.•The same admittance signal observed in cells with Pt and Mo back electrodes•The Meyer–Neldel behaviour may be related to phonon-assisted carrier capture.
This work contributes to the discussion on defect levels in Cu(In, Ga)Se-2 photovoltaic material. CuInSe2- and Cu(In, Ga)Se-2-based Schottky junctions, solar cells and thin films were investigated ...using complementary capacitance and current spectroscopic techniques. Depending on the applied technique and type of investigated structure, six different signals were observed. Out of the signals identified, three were ascribed to responses from bulk defects-two electron and one hole trap. The remainder were discussed in light of available in-literature models including carrier mobility freeze-out and non-ohmic back junction.
The controversial issue of a source for the fill factor losses in Cu(In,Ga)Se2-based solar cells observed under red light is discussed. Experimental evidence is presented that removal of the fill ...factor loss by blue light is accompanied by a decrease in capacitance. Similar kinetics for both effects are observed. This effect is demonstrated not only on CdS-buffered devices but also on Zn(O,S)- and In2S3-buffered cells. The explanation, supported by simulations, is based on a model of a reduction of the p+ layer by holes photogenerated in the buffer. This effect might be differentiated from the effect of a photosensitive secondary barrier in the buffer-window part of the junction by a sign of the capacitance change under blue light.
► High-energy photons improve fill factor in Cu(In,Ga)Se2-based solar cells. ► The effect is demonstrated on three types of buffer layers. ► Fill factor improvement under blue light is correlated with a decrease of doping. ► p+ layer is the main cause of fill factor deficiency under red light.
Cu(In,Ga)Se2 (CIGSe) layers have been deposited by the 3-stage process and once the growth was completed, the structures have been kept at high temperature for 50min with or without Se supply. Both ...the resulting CIGSe layer and related device properties are compared with those obtained when the substrate is cooled down right after the deposition. Moreover, such experiments have been performed with and without alkali availability. The results show that keeping the absorber at high temperature differently impacts Ga/(In+Ga) atomic ratio distribution and crystalline preferential orientation depending on whether Se is supplied. Moreover, this work shows that chalcogen supply can be detrimental for cell performance when the CIGSe contains alkali and in contrast be beneficial when the CIGSe is free of alkali. These observations suggest an intimate relationship between alkali and Se.
•Annealing under Se flux appears detrimental if the absorber layer contains alkali.•The detrimental impact is due to increased interface recombination.•The same post-deposition treatment is beneficial if the absorber is alkali-free.•Alkali-free performance is improved thanks to increased net acceptor density.
This work reports on the effect of Na doping on hole concentration in CIGS thin film solar cells deposited on polyimide substrate. Two methods of Na supply were applied in this investigation: Na ...containing back contact layers (Mo:Na) and NaF evaporation at different stages of the absorber deposition, including the post-growth Na treatment. The results of hole concentration profiles are presented. The correlation of the hole concentration and the amount of supplied Na is discussed in view of growth- and defect-related models.
•Hole concentration in CIGS solar cells absorbers increases if sodium is provided into the absorber.•Different methods of Na supply are adequate to achieve high hole concentration.•Electrical activity of grain boundaries was proposed to have impact on hole concentration.•Proposed model was supported by performed simulations.
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