Light Current-voltage Research Articles

Charge Transport in Interband Cascade Lasers: An Ab‐Initio Self‐Consistent Model

AbstractInterband cascade lasers (ICLs) stand out due to their low threshold current and minimal power consumption, rendering them viable sources for compact and mobile devices in the mid‐infrared. Since their first demonstration, they experienced major performance improvements. Mostly they originate from either improved material quality or the outcomes of numerical analysis of secluded parts. Encouraged by the impact of secluded models, an ICL‐specific simulation tool can lead to performance breakthroughs and a better comprehension of governing mechanisms. Drawing from an evaluation of existing tools designed for quantum cascade structures, a self‐consistent density matrix rate equation model is implemented to simulate the transport in both conduction and valence band heterostructures. Albeit the extensive inclusion of the quantum effects, special care was taken to maintain a high numerical efficiency. The charge transport model additionally considers optical field calculations, allowing for predictive calculations of light–current–voltage curves. The model is benchmarked against well‐established ICL designs and demonstrate reliable performance predictability. Additionally, detailed insights into device characteristics extracted from the model are provided. This ultimately allows to deepen the understanding of ICL and not only refine existing ones but also generate novel optimized designs.

Analysis of the Influence of Formation of Pd Silicides on Surface Layers of Si on the Diffusion of Atoms of Contacting Metal

4-probe measurements of surface resistivity, measurements of dark and light current-voltage characteristics, the possibilities of using a thin PdSi film to obtain perfect nano-sized ohmic contacts on the Si(111) surface have been investigated using Auger electron spectroscopy methods in combination with ion etching of the surface. It has been shown that the depth of Ni diffusion in the Ni-Si (111) system is 400 ‑ 500 Å at indoor temperature, and 70 – 80 Å in the Ni-PdSi-Si (111) system. The quality of the ohmic contact in the latter case does not change up to T = 800 K and withstands luminous flux illumination up to F = 1100 lux. It is shown that the resistivity of the PdSi film passes through a minimum at T = 900 – 1000 K. An analysis of the results obtained will be given in the article.

Impact of pre and post-perovskite infiltration treatments on monolithic perovskite solar cell performance

Carbon-based monolithic perovskite solar cells (mPSCs) represent an enticing frontier in the domain of organic–inorganic hybrid solar cells, capturing substantial research attention due to their cost effectiveness and straightforward fabrication process. Despite these merits, the challenge of achieving uniform pore filling in mPSCs, especially within mesoporous layers comprising titania, zirconia, and carbon alongside perovskite, persists. The uncontrolled and confined crystallization of the perovskite precursor within these mesoporous layers warrants meticulous investigation. This study addresses the issues related to uncontrolled crystallization by employing temperature-assisted infiltration techniques spanning from room temperature to 70 °C across triple mesoporous scaffolds. Devices were intricately fabricated using a semi-automatic drop-casting procedure, incorporating a (5-AVA)x(MA)1−xPbI3-mixed cation perovskite. Following infiltration, comprehensive pore filling of oxide layers was achieved through chlorobenzene-assisted antisolvent treatment. Comparisons were made between chlorobenzene-assisted and untreated samples under ambient conditions and thermal stress (40–70 °C). The temperature-dependent effects on perovskite infiltration and recrystallization were systematically investigated through dark and light current–voltage (J–V) characteristics, Impedance Spectroscopy (IS), and X-ray Diffraction (XRD) analyses. The findings revealed that the optimum power conversion efficiency (PCE) of 13.34% was attained when perovskite infiltration occurred at 40 °C with antisolvent treatment. Dark J–V and IS results indicated that temperature-assisted infiltration not only stimulated charge transfer but also effectively suppressed recombination. Under chlorobenzene treatment, XRD peaks exhibited broadening, indicating a reduction in perovskite crystallite size. This phenomenon facilitated the development of perovskite crystals across all available mesoporous spaces, leading to an enhanced interface property conducive to efficient charge transfer. The insights gleaned from this study on the controlled crystallization of perovskite precursors within mesoporous layers hold significant promise for advancing the stability and efficiency of mPSCs.

Interband cascade light-emitting diodes grown on silicon substrates using GaSb buffer layer

Interband cascade light-emitting diodes (ICLEDs) offer attractive advantages for infrared applications, which would greatly expand if high-quality growth on silicon substrates could be achieved. This work describes the formation of threading dislocations in ICLEDs grown monolithically on GaSb-on-Silicon wafers. The epitaxial growth is done in two stages: the GaSb-on-Silicon buffer is grown first, followed by the ICLED growth. The buffer growth involves the nucleation of a 10-nm-thick AlSb buffer layer on the silicon surface, followed by the GaSb growth. The AlSb nucleation layer promotes the formation of 90° and 60° interfacial misfit dislocations, resulting in a highly planar morphology for subsequent GaSb growth that is almost 100% relaxed. The resulting GaSb buffer for growth of the ICLED has a threading dislocation density of ∼107/cm2 after ∼3 μm of growth. The fabricated LEDs showed variations in device performance, with some devices demonstrating comparable light–current–voltage curves to those for devices grown on GaSb substrates, while other devices showed somewhat reduced relative performance. Cross-sectional transmission electron microscopy observations of the inferior diodes indicated that the multiplication of threading dislocations in the active region had most likely caused the increased leakage current and lower output power. Enhanced defect filter layers on the GaSb/Si substrates should provide more consistent diode performance and a viable future growth approach for antimonide-based ICLEDs and other infrared devices.

Prevention of potential‐induced degradation using a moisture barrier in crystalline silicon photovoltaic modules

AbstractAs photovoltaic (PV) modules are exposed to high temperatures and humidity over time, they generate leakage current, which leads to potential‐induced degradation (PID) and lower power output. In silicon, Cu(In,Ga)(Se,S)2 (CIGS) thin film and perovskite solar cells, PID has been shown to be driven by the presence of Na in the module glass. PID stability is crucial for the commercialization of such solar modules. This study aims to confirm the leaching phenomenon of Na in soda–lime module glass and study the use of polytetrafluoroethylene (PTFE) as a moisture barrier to prevent PID. By water immersion and exposure to different temperature and humidity conditions, we exhibited Na leaching in soda–lime glass. Moreover, we demonstrate the use of an anti‐PID moisture barrier made of PTFE, which was deposited using kinetic spraying between the cover glass and encapsulant in the solar module. The thickness of the moisture barrier was controlled by adjusting the deposition rate, and the PID characteristics were evaluated by manufacturing solar modules for different barrier thicknesses. Light current–voltage (LIV), dark current–voltage (DIV), and electroluminescence (EL) measurements confirmed that the PTFE moisture barrier effectively inhibits the degradation of solar cells. This study provides further insights into the Na leaching phenomenon and PID mechanism in PV modules and contributes to the design and development of more stable solar cells.

Analytical model of light current-voltage characteristics of a solar cell based on experimental data

In this work, a modified experimental method for calculating the parameters of the one-exponential equation of the light current-voltage characteristic of solar cells has been developed using approximation and verification of experimental data. This approach allowed us to create a more accurate mathematical model of such characteristics. It has been confirmed that the approximation equation of the open circuit voltage versus short circuit current contains the necessary data to establish the numerical values of the p-n junction parameters: the imperfection factor and the saturation current of the one-exponential model of the light current-voltage characteristics of a solar cell. A comparison between the experimentally measured results and those predicted by the mathematical model results allowed not only to correctly determine the values of the parameters of the one-exponential equation of light current-voltage characteristics, but also to identify instrumental and computational errors in the experimental studies. An expression for calculating the series resistance based on verified current and voltage values at the point of maximum power was derived. In cases where the current or voltage values at the maximum power point are questionable, the determination of the series resistance value is possible using numerical methods for solving the equation of the single-exponential model in a narrow range of the light current-voltage characteristic curve in the vicinity of the maximum power point. The use of algorithms in maximum power point tracking systems that more reliably determine its coordinates increases the efficiency of these systems and the output power delivered to the load.

Monitoring and Diagnostic Method for Maintaining the Operation Parameters of a Solar Module under Non-Uniform Illumination

The most well-known methods for diagnosing solar modules are considered; it is shown that the described diagnostic methods do not allow identifying defects that develop over a long time. The operation of photovoltaic cells under non-uniform illumination is analyzed. It has been shown that the operation of solar modules under non-uniform illumination can lead to thermal damage to semiconductor materials and deterioration in the module energy characteristics due to the fact that some of the photovoltaic cells located at reduced energy illumination become a parasitic load for more illuminated photovoltaic cells included in such module. An analytical equation has been obtained in explicit form for the full current-voltage characteristic of a photovoltaic cell using the Lambert W-function in forward and reverse bias, which makes it possible to study the connections of photovoltaic cells as a part of a solar module under non-uniform energy illumination, where the reverse branch of the current-voltage characteristic is important. The analytical equation makes it possible to predict the behavior of photovoltaic cells and solar modules composed of them under various operating modes, including identifying the degradation process. An electronic measuring device has been developed and manufactured that makes it possible to measure the light and dark current-voltage characteristics of a photovoltaic cell, including the negative branch, in automatic mode. This reduces measurement time and the influence of external experimental conditions when obtaining the current-voltage characteristics of the photovoltaic cell. A method for constructing solar modules from photovoltaic cells under conditions of their operation under non-uniform lighting has been proposed. As a result of such selection, reliability is increased and an increase in the efficiency of the solar module in shading mode, composed of series-connected photovoltaic cells selected in this way, is achieved.

Experimental approval of the working modes of the Sunbrick sun simulator

Commissioning and experimental testing of technical capabilities and modes of operation were carried out, and test measurements of light current-voltage characteristics of solar cells were carried out using a modern measuring complex based on the Sunbrick sun simulator. Automated measurement of the light-voltage-current characteristics of solar cells by the compensation method using the Keithley 2400 measuring device was implemented. During the approbation of the measuring complex based on the Sunbrick sun simulator, the possibility of reproducing different modes of simulator operation was tested and the ability to control radiation in terms of energy in the range from 100 to 1100 W/m2 and by spectral composition. It was established that the spatial unevenness of illumination for the investigated device is less than 2 % with an illumination area of more than 400 cm2. It is shown that the tested measuring complex allows for automated research of solar cells in irradiation regimes corresponding to both terrestrial irradiation conditions and extraatmospheric solar radiation conditions. The possibility of individual adjustment of each of the 36 channels of the emitting element in the range from 400 to 1100 nm has been tested, which adds flexibility in the use of the Sunbrick sun simulator during the study of both solar cells as a whole and the properties of functional semiconductor materials by irradiation with monochromatic or mixed illumination. It is shown that due to the rapidity of conducting research and the ability to immediately visualize the measured current-voltage characteristic on the computer screen, it is possible to significantly speed up the process of researching solar cells. Thus, it is possible to immediately divide the investigated solar cells into groups in relation to their efficiency and determine the presence of possible defects or damage in their structure.

Polarization-stable single-mode multi-junction VCSELs with integrated anti-phase mode filter

In this paper, polarization-stable and spectrally single-mode operation of oxide-confined multi-junction vertical-cavity surface-emitting lasers (VCSELs) are achieved by using a non-circular integrated anti-phase transverse mode filter. A record-high single-mode output power is obtained by radially reducing effective mirror reflectivity at the surface areas where the higher order modes are expected to lase, leading to an increase in the threshold gain for these transverse modes, all the while minimal losses are introduced to the fundamental mode. The polarization control of such devices is achieved by using a non-circular mode filter in order to perturb the cylindrical symmetry of the cavity. An elliptically etched surface relief is shown to be effective in realizing a single-mode single-polarization device over a wide range of operating bias currents and temperatures. The continuous-wave light–current–voltage characteristics of 8-junction 940 nm VCSELs show single-mode output power >13 mW at room temperature, spectrally measured with a side-mode suppression ratio of >30 dB. This single-mode performance can be achieved depending on the ratio between the relief opening and the oxide aperture size. Additionally, the single-polarization behavior of such devices (with an extinction ratio of >15 dB) is shown to be dependent on the orientation of the elliptical mode filter, where the light is mainly polarized along the minor axis of the elliptical feature. Overall, combined with a multi-junction active region, the elliptical model filter is able to achieve highly efficient single-mode linearly polarized VCSELs.

Effects of neutron radiation on the key component cells of upright metamorphic four-junction (UMM4J) solar cells

In this study, the bandgap of the top three junctions of the UMM4J solar cell was optimized based on the spectral matching principle. Three materials, namely AlGaInP (1.957 eV), AlInGaAs (1.495 eV), and InGaAs (1.171 eV), were selected as the materials for the top three sub-cells. The component cells were fabricated using metal organic chemical vapor deposition (MOCVD) to verify their radiation resistance performance. Neutron irradiation with an equivalent energy of 1 MeV and a fluence of 6 × 1013 cm−2 was used to evaluate the end-of-life performance. The light current-voltage (LIV) and external quantum efficiency (EQE) results reveal that the AlGaInP (1.957 eV) component cells demonstrate superior radiation resistance performance, while the InGaAs (1.171 eV) component cells exhibit the poorest radiation resistance performance. After ensuring a sufficient margin of degradation for the InGaAs (1.171 eV) sub-cells, the AlInGaAs (1.495 eV) component cells serve as the current-limiting junction before and after radiation, resulting in an enhanced radiation hardness of the UMM4J solar cell. Furthermore, deep level transient spectroscopy (DLTS) was employed to directly assess the radiation-induced defects of the three-component cells. The degradation of solar cell performance primarily stems from the defects that induce Shockley-Read-Hall (SRH) recombination.

Screen printable fire through nickel contacts for silicon solar cells

Metallization of crystalline silicon (Si) solar cells is indispensable for reducing the cost while increasing the overall efficiency. Developing alternative materials to the most commonly used screen printed silver (Ag) contacts is a critical factor. Here, in this study, a nickel (Ni) metal paste consisting of Ni metal particles, glass frit and an organic vehicle is fabricated for screen printed Ni contacts. To prevent possible Schottky barrier formation, a graphene layer is placed on the front surface of the Si solar cell between Ni and Si forming a metal-2D-semiconductor structure ensuring the ohmic (or ohmic-like) contacts. It is demonstrated here that the graphene is transferred successfully onto the textured front surface of the cells and G/2D peaks are observed clearly, indicating the good quality of the graphene layer. Constituents of Ni metal paste, glass frit and organic vehicle, are fabricated in concordance with nickel metal powder and mixed to achieve optimal electrical output parameters. The findings suggest that the transition temperature of the glass frit is between 270 °C and 300 °C resulting in around 475 °C softening temperature, which gives excellent etching behavior to the paste. The average contact resistance of the screen printed Ni contacts governed by etching process is measured around 6.9 mΩ cm2. The SEM images of the contacts show a uniform distribution and sintering behavior similar to that of silver counterparts. The light current-voltage measurements read the open circuit voltage of 660 mV, the short circuit density of 39.11 mA/cm2 and the fill factor of 81.4% resulting in around 21% efficiency.

Efficiency boost of inverted polymer solar cells using electrodeposited n-type Cu<sub>2</sub>O electrons selective transport layers (ESTLs)

Polymer solar cells (PSCs) have attracted tremendous interest as suitable candidates for harnessing solar energy in the recent years. The inherent optoelectronic properties of the inorganic transition metal oxide, negative type cuprous oxide (n-Cu2O), makes it an attractive candidate to improve the performance of PSCs when incorporated as the electron selective transport layers (ESTLs) in the device. In this study, inverted PSCs were fabricated on stainless steel (SS) substrates with n-Cu2O as the ESTL. The n-Cu2O films were prepared by electrodeposition method, followed by annealing under ambient conditions. The active layer material was prepared as bulk heterojunction blend using regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM). Poly-(4,3-ethylene dioxythiophene):poly(styrenesulphonate) (PEDOT:PSS) was used as the hole transport layer (HTL) and the final device structure was SS/n-Cu2O/P3HT:PCBM/PEDOT:PSS/Au. Annealing of the n-Cu2O ESTL in air was optimized observing the photoactive performance of the device. Optoelectronic performance of the devices was characterized using spectral response and dark and light current-voltage (I-V) measurements. n-Cu2O ESTL- incorporated devices have absorbed more photons in the short wavelength region of 450‒600 nm with the annealing of n-Cu2O ESTL due to the reduction of electron-hole recombination. The performance of the devices was significantly increased after incorporating pre-annealed n-Cu2O ESTL at 175 °C for 30 min in air. The maximum power conversion efficiency (PCE) was 0.35%.

High Slope Efficiency Double and Triple Junction 808 nm Vertical Cavity Surface Emitting Lasers

High-performance 808 nm double and triple-junction vertical cavity surface emitting lasers (VCSELs) are designed and investigated. The light-current-voltage (L-I-V) characteristics of 808-nm single, double, and triple-junction VCSELs are compared. In the paper, the double-junction VCSELs with two oxide apertures exhibit a very high slope efficiency (SE) of 2.32 W/A at 25 °C, and the peak SE of 2.51 W/A is achieved at 10 °C. The power conversion efficiency (PCE) of 53.14% is achieved for double-junction individual VCSEL emitter. The peak SE of the triple-junction VCSELs reach 3.40 W/A with the PCE of 53.02% for individual VCSEL emitter. Under narrow pulse test conditions (400 Hz, 60 ns pulse width), the peak output powers of the designed double-junction and triple-junction VCSEL arrays reach 216.11 W and 325.77 W under the injection current of 80 A, respectively. Such high-performance multi-junction 808-nm VCSELs are very important for pumping solid state lasers and medical aesthetics.

Effects of proton radiation on the InGaAs component cells of inverted metamorphic four-junction solar cells

In this study, 5-MeV proton radiation was incident on the InGaAs (1.0 eV) and InGaAs (0.7 eV) component cells of inverted metamorphic four-junction (IMM4J) solar cells. Light current–voltage (LIV), external quantum efficiency (EQE), and deep level transient spectroscopy (DLTS) were used to examine the performance degradation and the radiation defects. For the two InGaAs component cells, in case of LIV, open circuit voltage (Voc), short-circuit current (Isc), and the maximum output power (Pmax) decreased linearly with the function of logarithmic change of the proton fluence. Compared to InGaAs (1.0 eV) component cells, for the InGaAs (0.7 eV) component cells, Voc and Pmax decreased considerably and Isc decreased slightly. In EQE, an evident measurement artifact related to the luminescence coupling effect was detected in InGaAs (1.0 eV) before proton radiation, and it disappeared after radiation. This phenomenon was not observed in InGaAs (0.7 eV). In DLTS, a hole trap, H0, was detected at Ev + 0.09 eV in InGaAs (1.0 eV), and three hole traps H1, H2, and H3, were detected at Ev + 0.07 eV, Ev + 0.30 eV, and Ev + 0.45 eV, respectively, in InGaAs (0.7 eV). H0 and H1 were attributed to shallow traps introduced during radiation, and H2 and H3 were the initial defects due to the growth process; moreover, H2 and H3 were determined to be VGa (0/-1) and VGa(-1/-2) or probably VAs(+3/+1).

Heavily Ge-doped GaN as transparent current spreading layer for blue tunnel junction light emitting diodes

We report on metalorganic vapor phase epitaxy of highly conductive germanium-doped GaN layers and their application for blue tunnel-junction light emitting diodes (TJ-LEDs). Using Ge as donor, carrier densities of up to 2 × 1020 cm−3 and low bulk resistivities down to 3 × 10−4 Ωcm are achieved. Under optimum growth conditions, no degradation of the crystalline quality is observed and layers exhibit high transparency making GaN:Ge very attractive as current spreading layer in light emitting devices. We have realized GaN-based TJ-LEDs by capping conventional InGaN LED structures with highly doped GaN:Ge. Such TJ-LEDs withstand operation currents up to 20 kA/cm2 in continuous and up to 60 kA/cm2 in pulsed operation conditions. Moreover, TJ-LEDs exhibit homogeneous electroluminescence and light output through the top surface that is increased by more than 60% as compared to conventional LEDs with transparent indium tin oxide contacts. The impact of the doping profile, carrier gas conditions, and acceptor activation by annealing for low-resistive TJ characteristics is discussed. Light output and current voltage characteristics of blue-light emitting devices with GaN-TJ are presented at low and high-current densities.

Electrical and optical properties of Schottky diodes fabricated by electrodeposition of Ni films on n-GaAs

In this paper, we report electrical and optical characteristics of the Schottky diodes fabricated by electrodeposition of nickel onto n -GaAs substrate from 0.125 M NiSO 4 + 0.25 M H 3 BO 3 + 0.25 M Na 2 SO 4 solution. The electrodeposition was performed at room temperature and at − 1.5 V vs. SCE. Electrical and optical properties were measured in the temperature range of 200–360 K. Dark and light current-voltage ( I-V ) characteristics were investigated. Ideality factor, n and zero-bias barrier height, ϕ b were calculated and found to be almost constant in this temperature range. For room temperature, these values were obtained as 1.05 and 0.70 eV, respectively. Illuminated I-V characteristics were also investigated and they showed that the fabricated device could operate in photovoltaic regime. Open-circuit voltage, V oc was found to be 0.24 V for the diode under 20 mW/cm 2 illumination. • Good light sensitivity is achieved by electrodeposition. • Room temperature n and ϕ b values are 1.05 and 0.70 eV, respectively. • Electrodeposited Ni/ n -GaAs Schottky diode can operate in photovoltaic regime.

Optimization of the Electrode Formation Mechanism for Crystalline Silicon Heterojunction Solar Cells

The screen-printing process for making good contact of electrodes with the top layer of solar cells is crucial for enhancing the electrical properties of a solar cell. This paper reports the experimental approach adopted for the process of electrode formation and the resulting shape of electrodes in silicon-based heterojunction (SHJ) solar cells. It was observed that good contact between electrodes and the top transparent conductive oxide (TCO) layer strongly depends on the squeegee pressure, curing temperature, and curing time. By optimizing the squeegee pressure at 0.350 MPa, snap-off distance of 1.4 mm, squeegee speed of 80 mm sec−1, curing temperature of 180 °C, and curing time of 30 min, respectively for which the height to width ratio (aspect ratio) of the fabricated electrodes was achieved around 0.66. The results have been verified through 3D laser profiler, field emission scanning electron microscopy (FE-SEM), transfer length method (TLM), and Light current-voltage (LIV) measurements. The SHJ solar cells were fabricated using an optimized condition and successfully achieved splendid properties of short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), and efficiency (η) up to 40.57 mA cm−2, 723 mV, 81.03%, and 23.79%, respectively.

Biophysical characterization of light-gated ion channels using planar automated patch clamp.

Channelrhodopsins (ChRs) are proteins that guide phototaxis in protists and exhibit light-gated channel conductance when their genes are heterologously expressed in mammalian cells. ChRs are widely used as molecular tools to control neurons and cardiomyocytes with light (optogenetics). Cation- and anion-selective ChRs (CCRs and ACRs, respectively) enable stimulation and inhibition of neuronal activity by depolarization and hyperpolarization of the membrane, respectively. More than 400 natural ChR variants have been identified so far, and high-throughput polynucleotide sequencing projects add many more each year. However, electrophysiological characterization of new ChRs lags behind because it is mostly done by time-consuming manual patch clamp (MPC). Here we report using a high-throughput automated patch clamp (APC) platform, SyncroPatch 384i from Nanion Technologies, for ChR research. We find that this instrument can be used for determination of the light intensity dependence and current-voltage relationships in ChRs and discuss its advantages and limitations.

ACTIVATION METHOD OF CADMIUM TELLURIDE THIN FILMS FOR CREATION EFFECTIVE SOLAR CELLS

The influence of annealing in freon on the cadmium telluride films crystal structure obtained by closed space sublimation method and the output parameters and light diode characteristics of solar cells based on these films were studied. Annealing of structures was performed at a temperature of 400°С for different times. The studies of the crystal structure were performed by the X-ray diffraction analysis. These studies have shown that the annealing in freon leads to a recrystallization of cadmium telluride films, which reduces microstress. It is evidenced by the lattice period decrease after annealing from а = 6.491 Å to а = 6.488 Å. The study of the influence of annealing in freon on the output parameters and light diode characteristics of solar cells was performed. For this purpose the light current-voltage characteristics of ITO/SnO2/CdS/CdTe structures, annealed for 20‑40 minutes, were studied. It was found that the optimal annealing time in freon is 30 minutes. It is shown that the solar cells based on such films have the highest efficiency in 11.7% after annealing in freon for 30 minutes. A simulation of light diode characteristics influence on the efficiency showed that the solar cells efficiency increase due to the diode saturation current density decrease when the annealing time in freon increases to 30 minutes. When the annealing time increases to 40 minutes the efficiency decrease is associated with a shunt resistance decrease. It is also shown that the pre-irradiation of solar cells in the AM1.5 mode for 20 minutes leads to an additional efficiency increase to 12.2%. According to the simulation results, such efficiency increase is also due to the diode saturation current density decrease.

Characterization of Potential-Induced Degradation and Recovery in CIGS Solar Cells

The potential-induced degradation (PID) mechanism in Cu(In,Ga)(Se,S)2 (CIGS) thin-film solar cells, which are alternative energy sources with a high efficiency (>23%) and upscaling possibilities, remains unclear. Therefore, the cause of PID in CIGS solar cells was investigated in this study at the cell level. First, an appropriate PID experiment structure at the cell level was determined. Subsequently, PID and recovery tests were conducted to confirm the PID phenomenon. Light current–voltage (I–V), dark I–V, and external quantum efficiency (EQE) analyses were conducted to determine changes in the cell characteristics. In addition, capacitance–voltage (C–V) measurements were carried out to determine the doping concentration and width of the space charge region (SCR). Based on the results, the causes of PID and recovery of CIGS solar cells were explored, and it was found that PID occurs due to changes in the bulk doping concentration and built-in potential at the junction. Furthermore, by distinguishing the effects of temperature and voltage, it was found that PID phenomena occurred when potential difference was involved.