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Iron pyrite [cubic FeS2 (cFeS2)] is considered as an earth-abundant and low-cost thin-film photovoltaic material. However, the conversion efficiency of cFeS2-based solar cells remains below 3%. To elucidate this limitation, we evaluate the optical and electrical characteristics of cFeS2 single crystals that are grown using the flux method, thus providing us an understanding of the electron transport behavior of cFeS2 single crystals. The oxide layer on the surface of cFeS2, which can possibly have an influence on the electrical characteristics of cFeS2, is removed prior to characterization via optical spectroscopy and electrical transport measurement. The optical property of cFeS2 was found to have both indirect and direct transitions. We also observed the presence of a band tail below the conduction band. The obtained electrical transport behavior indicates that cFeS2 bulk exhibits a high defect density and a disordered phase, thus leading to the hopping conduction mechanism. Our results will pave the way for the development of photovoltaic applications with iron pyrite.

Extensive research on fault diagnosis is essential to detect various faults that occur to different photovoltaic (PV) panels to keep PV systems operating at peak performance. Here, we present an impact analysis of potential induced degradation (PID) on the current–voltage (I-V) characteristics of crystalline silicon (c-Si) solar cells. The impact of parasitic resistances on solar cell performance is highlighted and linked to fault and degradation. Furthermore, a Simulink model for a single solar cell is proposed and used to estimate the I-V characteristics of a PID-affected PV cell based on experimental results attributes. The measured data show that the fill factor (FF) drops by approximately 13.7% from its initial value due to a decrease in shunt resistance (Rsh). Similarly, the simulation results find that the fill factor degraded by approximately 12% from its initial value. The slight increase in measured data could be due to series resistance effects which were assumed to be zero in the simulated data. This study links simulation and experimental work to confirm the I-V curve behavior of PID-affected PV cells, which could help to improve fault diagnosis methods.

Herein, enhancements in thermoelectric (TE) performance, both the power factor (PF) and thermal stability, are exhibited by sandwiching HfO2 and TiO2 layers onto atomic layer deposited-ZnO thin films. High-temperature TE measurements from 300 to 450 K revealed an almost two-fold improvement in electrical conductivity for TiO2/ZnO (TZO) samples, primarily owing to an increase in carrier concentration by Ti doping. On the other hand, HfO2/ZnO (HZO) achieved the highest PF values owing to maintaining Seebeck coefficients comparable to pure ZnO. HZO also exhibited excellent stability after multiple thermal cycles, which has not been previously observed for pure or doped ZnO thin films. Such improvement in both TE properties and thermal stability of HZO can be attributed to a shift in crystalline orientation from the a axis to c axis, as well as the high bond dissociation energy of Hf-O, stabilizing the ZnO structure. These unique properties exhibited by HZO and TZO thin films synthesized by atomic layer deposition pave the way for next-generation transparent TE devices.

We report the enhancement in the electrical performance of solution-processed amorphous InZnO ( $a$ -IZO) thin-film transistors (TFTs) through incorporation of low-temperature photosensitive polysilsesquioxane (P-PSQ) passivation. P-PSQ passivated TFTs recorded smaller ${V}_{th}$ shift of 1.5 V after positive bias stress test despite annealing at 180°C. Analysis of secondary ion mass spectrometry and x-ray photoelectron spectroscopy showed that higher concentration of hydrogen reduced the amount of oxygen vacancies in the passivated IZO channel which promotes better stability against bias stress. Also, the time evolution of the ${V}_{th}$ was defined in which the activation energy for each sample was extracted. Passivated TFT also showed minimal change upon exposure to humidity test. Overall, low-temperature P-PSQ passivation is an effective barrier against atmospheric effects for solution-processed oxide TFTs.

A mechanism of potential induced degradation (PID) delay effect by ultraviolet (UV) light irradiation during PID test for p-type crystalline silicon (c-Si) solar cells was proposed in this work. The degradation rate of the solar cell performances is slowed down by the UV light irradiation in the 300–390 nm wavelength range during PID test. The conductivity increase of the silicon nitride (SiNx) anti-reflection coating (ARC) layer on the solar cell surface under UV light irradiation during PID tests, which relates to the mechanism preventing the penetration of sodium ions into the active cell layer, induces the PID delay effect for the p-type c-Si solar cells. The PID delay effect was also analyzed by a microwave photo-conductance decay (μ-PCD) technique in this work. The reduction behavior of the components in the μ-PCD signal curves including rapid (τ1) and slow (τ2) decay time constants and the effective lifetime (τeff) presents a good correlation with the performance degradation behavior of the solar cells over PID test duration. Moreover, the reduction rate of these components is also slowed down under the UV light irradiation in the 300–390 nm wavelength range during PID tests. Notably, their reduction behavior was compatible with the mechanism of the conductivity increase of the SiNx ARC layer under UV light irradiation.

We report a chemical sensor that exhibits high reliability and long-term stability; this is achieved by employing an amorphous oxide semiconductor (AOS) as a channel material in an extended-gate th...

Herein, a core–shell heterostructure of H2O-oxidized ZnO nanorod (NR)@Mg-doped ZnO (MZO) nanoparticles (NP) with superior charge transfer capabilities is presented for the first time. ZnO NRs were strategically designed using a low-temperature and sustainable H2O oxidation technique and followed by low-temperature annealing of a spin-coated MZO precursor to form a core–shell heterostructure. Surface morphological and nanobeam electron diffraction (NBD) analysis validated the high-quality crystalline nature of the core–shell heterostructure. The verification of Mg dopant inclusion in the ZnO lattice and uniform distribution were established from X-ray (XRD, XPS, EDX), Raman and electron energy-loss (EELS) spectroscopy analyses. The ZnO NR@MZO NP core–shell film preserved the excellent transparency of the original ZnO NRs and displayed the highest conductivity due to the increased carrier concentration in the MZO shell. Steady-state photoluminescence (PL) intensity of the perovskite film on top of the ZnO NR@MZO NP core–shell film showed the strongest quenching among the samples indicating the fastest electron transfer. This ZnO NR@MZO NP core–shell heterostructure could provide a more efficient transmission channel by supplying a larger electronic contact with the light absorber layer and a direct path for electron transport to the cathode. Ultimately, our results highlight the great potential of the ZnO NR@MZO NP core–shell structure as an electrode not only for photovoltaics but also in other future flexible optoelectronic devices.

This research investigated the optical properties of silicon-rich silicon nitride (Si-rich SiN) and conventional silicon nitride (SiNx) layers, which are commonly used in anti-reflective coating (ARC) to improve the light absorption in solar cells. We found that the change in the refractive index of Si-rich SiN was due to the annealing temperature that was considerably higher than that of conventional SiNx. In addition to the mass density variation in the SiNx layer that generally governed the change of refractive index in previous studies, this study found another important factor influencing the change of the refractive index. The Si–N bond, which was the main component in SiNx controlled the refractive index, while the amount of Si-Si bond in Si-rich SiN after annealing governed the change of the refractive index. The structural analysis presented for the Si-rich SiN and the SiNx explained the effect of the annealing process on tuning the refractive index of the Si-rich SiN.

Perovskite/silicon tandem solar cells are considered a low-cost solution to overcome the silicon solar cells’ performance restriction. Light management is a potential approach in the improvement of their efficiency. In this work, we simulate and optimize 4-terminal perovskite/silicon heterojunction tandem solar cells with efficient light management using a silicon nitride layer as an index matching layer instead of the intermediate air medium layer between their top and bottom cells. Also, we demonstrate the effect of the index matching layer on their performance. With this approach, their efficiency enhances from 29.52% to 34.23%.

Herein, enhancements in thermoelectric (TE) performance, both the power factor (PF) and thermal stability, are exhibited by sandwiching HfO

We report the photo-assisted processing of solution-processed ultra wide bandgap oxide (E g ≥4.8 eV), amorphous gallium oxide (a-GaO x ), to enhance its conductivity. The 12-nm-thick a-GaO x ), film was subjected to UV treatment at 115°C for 60 min. The results show that UV treatment induced a minimal change in the electrical properties unlike what is observed in other wide band gap (E g ~ 3 eV) oxide materials, such as a-InZnO and a-InGaZnO.

Flexible and high-efficiency thermoelectric devices can be achieved by relying on three-dimensional nanostructures fabricated by proximity-field nanopatterning (PnP) process. In this study, the phase shift mask, which generates the light diffraction in the photoresist, has been studied. To enhance device performance, the size limitation of the mask for this process was investigated as well as how the mask affects the device performance in light propagation simulations. Results show that decreasing the nanostructure size by altering the periodicity from 0.60 µm to 0.30 µm results in 50 % filling factor (FF). To summarize, the mask periodicity 0.30 µm is the size limitation performed by simulation, and the mask periodicity 0.40 µm is an exciting candidate for future work.

The electrical properties of SiO2/GaN metal-oxide-semiconductor capacitors with different SiO2 thicknesses are evaluated before and after postmetallization annealing (PMA). The distribution of charges in bulk SiO2 and the SiO2/GaN interface is estimated by analyzing the electrical properties. It is revealed that the net effective charges (Nf) tend to increase with decreasing SiO2 thickness before PMA. This indicates that the negative bulk charges are present uniformly, and the positive interface charges exist locally near the interface. In the sample after PMA, Nf tends to decrease with decreasing SiO2 thickness at the thin SiO2 region (

High-k amorphous SrTa2O6 (STA) thin films were successfully deposited by rf magnetron sputtering for gate insulators in thin-film transistor (TFT). Practical STA thin films with high dielectric constant of 41.8, wide band gap of 4.58 eV, and low leakage current of ~10−8 A/cm2 were obtained through by optimal sputtering condition. The TFTs with amorphous InGaZnO (IGZO) as a channel and STA as a gate insulator were fabricated and investigated for thinning effects of gate insulator on transfer characteristic. The IGZO-TFT with 70-nm-thick STA achieved high performance switching properties; (mobility of 14.9 cm2/(V·s), threshold voltage of 0.6 V, sub-threshold swing of 111 mV/decade, and on/off ratio of 1.0 × 1010). These characteristics are due to the large gate capacitance of 4.6 × 10−7 F/cm2 and low gate leakage current from use of STA.

In recent years, potential induced degradation (PID) has been a topic of interest to scientists because of its significant impact on performance deterioration of solar cells. Research has shown that the major cause of PID defects for p-type Si solar cells is sodium (Na) ion migration from the soda-lime glass through the encapsulation layer into the solar cell. However, limited scientific investigations have been done on the influence and mechanism of Na ion decorated micro-cracks on the evolution of PID. In this work, Na ion decoration in micro-cracks as the important mechanism causing PID in p-type crystalline Si solar cells is presented and discussed in detail. Furthermore, a model of PID mechanism due to micro-cracks is proposed.

Self-heating degradation in semiconductor devices generated by driving voltage is a serious problem in the development of highly reliable products. This letter focuses on oxide semiconductors, as a representative of flexible devices on which thermal accumulation on the substrate is critical. We propose a heat-suppressing thin-film transistor (TFT) structure to improve the reliability of transparent amorphous oxide semiconductor TFTs. Findings from this letter indicate that a structure with a curved line, such as a Corbino disk, is effective for suppressing self-heating. Based on these results, we suggest a U-shaped TFT as a heat-suppressing structure and demonstrate its device simulation and thermal analysis.

We report a novel preparation method for a graphene/TiO2 nanohybrid using a supramolecular biomaterial (CDT1). CDT1 can offer an increase in the dispersibility of graphene in water and subsequent complexation of graphene and TiO2. This nanohybrid was applied to a perovskite solar cell and success was achieved in improving its photoelectric conversion efficiency.

Perovskite solar cells have attracted much attention as next-generation solar cells because of their high efficiency and low fabrication costs. Moreover, perovskite solar cells are a promising candidate for indoor energy harvesting. We investigated the effect of bandgap tuning on the characteristics of triple cation-based perovskite solar cells under fluorescent lamp illumination. According to the current density–voltage curves, perovskite solar cells with a wider bandgap than the conventional one exhibited improved open-circuit voltage without sacrificing short-circuit current density under fluorescent lamp illumination. Moreover, the wider bandgap perovskite films including a large amount of bromine in the composition did not show phase segregation, which can degrade the photovoltaic performance of perovskite solar cells, after fluorescent lamp illumination. Our results demonstrate the facile strategy to improve the performance of perovskite solar cells under ambient lighting and great potential of perovskite solar cells for indoor applications such as power sources for the internet of things.

Low temperature process is required to fabricate high performance amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) on plastic substrates for flexible display applications. In addition, high-k material which allows higher mobility, higher drain current and lower threshold voltage while facilitating miniaturization, is poised to replace conventional SiO 2 gate insulators in TFTs. Therefore, hybrid material containing high-k BaTiO 3 nanoparticles and transparent Poly-siloxane (Poly-SX) were used as gate insulator in a-IGZO TFTs. Opting for a hybrid material instead of only a BaTiO 3 film enables lowering of process temperatures. This paper presents the performance of a-IGZO TFTs with solution processed hybrid gate insulators at different BaTiO 3 /Poly-SX ratios deposited at a lower temperature (300°C). The device shows a high mobility of 30.17 cm2/Vs, low threshold voltage of 0.4 V, and leakage current density of ~10−8 A/cm2.

This research focused on the influence of ultraviolet (UV) light on the increase of conductivity properties of SiN x layers, which are utilized as an anti-reflective coating to improve the light absorption in silicon solar cells. We found that the SiN x conductivity increases significantly under the UV light, but it depends on the SiN x refractive index and is limited by SiN x bandgap. In this research, the correlation of the increase of SiN x conductivity with potential induced degradation (PID) for silicon solar cell was also discussed and proposed.

In order to investigate the role of SiNx anti-reflection coating in potential-induced degradation (PID) for p-type crystalline Si cells, PID tests were carried out using the cell without SiNx. PID did not occur with the module using the cell without SiNx even if the voltage of -2000 V was applied for 1 week. The simulation results of electric field distribution for the module without SiNx under applied voltage suggest that electric field is not be applied to cell-surface. Therefore, it is concluded that no electric field applied to SiNx is the most important to prevent PID.