In commercial solar cells, the pattern of the front electrode is critical to effectively assemble the photo generated current. The power loss in solar cells caused by the front electrode was categorized as four types. First, losses due to the metallic resistance of the electrode. Second, losses due to the contact resistance of the electrode and emitter. Third, losses due to the emitter resistance when current flows through the emitter. Fourth, losses due to the shading effect of the front metal electrode, which has a high reflectance. In this paper, optimizing the number of finger on a 4 ´ 4 solar cell is demonstrated with known theory. We compared the short circuit current density and fill factor to evaluate the power loss from the front metal contact calculation result. By experiment, the short circuit current density(Jsc), taken in each pattern as 37.61, 37.53, and 37.38 mA/ cm2 decreased as the number of fingers increased. The fill factor(FF), measured in each pattern as 0.7745, 0.7782 and 0.7843 increased as number of fingers increased. The results suggested that the efficiency(Eff) was measured in each pattern as 17.51, 17.81, and 17.84 %. Throughout this study, the short-circuit current densities(Jsc) and fill factor(FF) varied according to the number of fingers in the front metal pattern. The effects on the efficiency of the two factors were also investigated.

With the increase in installed solar energy capacity, comparison and analysis of the physical property values of solar cells are becoming increasingly important for production. Therefore, research on determining the physical characteristic values of solar cells is being actively pursued. In this study, a diode equation, which is commonly used to describe the I-V behavior and determine the electrical characteristic values of solar cells, was applied. Using this method, it is possible to determine the diode ideality factor (n) and series resistance (Rs) based on light I-V measurements. Thus, using a commercial screen-printed solar cell and an interdigitated back-contact solar cell, we determined the ideality factor (n) and series resistance (Rs) with a modified diode equation method for the light I-V curves. We also used the sun-shade method to determine the ideality factor (n) and series resistance (Rs) of the samples. The values determined using the two methods were similar. However, given the error in the sun-shade method, the diode equation is considered more useful than the sun-shade method for analyzing the electrical characteristics because it determines the ideality factor (n) and series resistance (Rs) based on the light I-V curves.

Silicon nitride (SiNx:H) films made by plasma enhanced chemical vapor deposition (PECVD) are generally used as antireflection layers and passivation layers on solar cells. In this study, we investigated the properties of silicon nitride (SiNx:H) films made by PECVD. The passivation properties of SiNx:H are focused on by making the antireflection properties identical. To make equivalent optical properties of silicon nitride films, the refractive index and thickness of the films are fixed at 2.0 and 90 nm, respectively. This limit makes it easier to evaluate silicon nitride film as a passivation layer in realistic application situations. Next, the effects of the mixture ratio of the process gases with silane (SiH4) and ammonia (NH3) on the passivation qualities of silicon nitride film are evaluated. The absorption coefficient of each film was evaluated by spectrometric ellipsometry, the minority carrier lifetimes were evaluated by quasi-steady-state photo-conductance (QSSPC) measurement. The optical properties were obtained using a UV-visible spectrophotometer. The interface properties were determined by capacitancevoltage (C-V) measurement and the film components were identified by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectroscopy detection (RBS) - elastic recoil detection (ERD). In hydrogen passivation, gas ratios of 1:1 and 1:3 show the best surface passivation property among the samples.

This study aimed to investigate antioxidant activities from 11 forest plants, and determine their total phenolics, flavonoids and proantocyanidins contents. In addition, the antioxidant activities were correlated with antioxidant compounds. Among the samples, Cornus officinalis, Castanea crenata, Lindera erythrocarpa, Carpinus laxiflora and Pourthiaea villosa showed significantly higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) (IC50=21.12~28.93 μg/mL) and 2,2’-azino-bis(3-ethylbenzothia zoline-6-sulfonic acid) (ABTS) (IC50=28.18~52.55 μg/mL) radical scavenging ability with reducing power (IC50=59.91~93.64 μg/mL) than other plants; and C. crenata, L. erythrocarpa and Rubus coreanus showed strong nitric oxide (NO) inhibition activity (≥60%). In addition, L. erythrocarpa, C. laxiflora and P. villosa showed higher oxygen radical absorbance capacity (ORAC) values (≥1,100 μM TE/g sample) than other samples. High total phenolic contents were observed in C. crenata (429.11 mg GAE/g), L. erythrocarpa (437.11 mg GAE/g), C. laxiflora (408.67 mg GAE/g) and P. villosa (404.11 mg GAE/g). The DPPH and ABTS radical scavenging activity with reducing power were significantly correlated with total phenolic contents (R2=0.71~0.79), but total phenolic contents were not correlated with NO inhibition and ORAC (R2=0.35~0.43). Therefore, these results suggested that C. officinalis, C. crenata, L. erythrocarpa, C. laxiflora and P. villosa are potential natural antioxidative candidate ingredients.

For rear metallization with Al paste, Al back contacts require good passivation, high reflectance, and a processing temperature window compatible with the front metal. In this paper, the effect of the firing ambient during the metallization process on the formation of Al rear metal was investigated. We chose three different gases as ambient gases during the firing process. Using SEM, we observed the formation of a back surface field in N2, O2, and Air ambients. To determine the effect of the ambient on Voc, the suns-Voc tool was used. In this study, we described the mechanism of burn-out of organic materials in Al paste during the firing process. The oxygen ambient plays an important role in the burn-out process. We calculated the efficiency with obtained the back surface recombination velocities using PC1D simulation. It was found that the presence of oxygen during the firing process influenced the uniform back surface field because the organic materials in the Al paste were efficiently burned out during heating. The optimized temperature with oxygen flow shows an absolute efficiency of 19.1% at PC1D simulation.

This paper presents the impact of partial shading on CuInxGa(1-x)Se2(CIGS) photovoltaic(PV) modules with bypass diodes. When the CIGS PV modules were partially shaded, the modules were under conditions of partial reverse bias. We investigated the characterization of the bypass diode and solar cell properties of the CIGS PV modules when these was partially shaded, comparing the results with those for a crystalline silicon module. In crystalline silicon modules, the bypass diode was operated at a partial shade modules of 1.67 % shading. This protected the crystalline silicon module from hot spot damage. In CIGS thin film modules, on the other hand, the bypass diode was not operated before 20 % shading. This caused damage because of hotspots, which occurred as wormlike defects in the CIGS thin film module. Moreover, the bypass diode adapted to the CIGS thin film module was operated fully at 60% shading, while the CIGS thin film module was not operated under these conditions. It is known that the bypass diode adapted to the CIGS thin film module operated more slowly than that of the crystalline silicon module; this bypass diode also failed to protect the module from damage. This was because of the reverse saturation current of the CIGS thin film, 1.99 × 10−5 A/cm2, which was higher than that of crystalline silicon, 8.11 × 10−7 A/cm2.

Solar cells exhibit different power outputs in different climates. In this study, the temperature dependence of open-circuit voltage(V-oc), short-circuit current(I-sc), fill factor(FF) and the efficiency of screen-printed single-crystal silicon solar cells were studied. One group was fabricated with homogeneously-doped emitters and another group was fabricated with selectively-doped emitters. While varying the temperature (25, 40, 60 and 80˚C), the current-voltage characteristics of the cells were measured and the leakage currents extracted from the current-voltage curve. As the temperature increased, both the homogeneously-doped and selectively-doped emitters showed a slight increase in I-sc and a rapid degradation of V-oc. The FF and efficiency also decreased as temperature increased in both groups. The temperature coefficient for each factor was calculated. From the current-voltage curve, we found that the main cause of V-oc degradation was an increase in the intrinsic carrier concentration. The temperature coefficients of the two groups were compared, leading to the idea that structural effects could also affect the temperature dependence of current-voltage characteristics.

The use of solar energy generation is steadily increasing, and photovoltaic modules are connected in series to generate higher voltage and power. However, solar panels are exposed to high-voltage stress (up to several hundreds of volts) between grounded module frames and the solar cells. Frequent high-voltage stress causes a power-drop in the modules, and this kind of degradation is called potential induced degradation (PID). Due to PID, a significant loss of power and performance has been reported in recent years. Many groups have suggested how to prevent or reduce PID, and have tried to determine the origin and mechanism of PID. Even so, the mechanism of PID is still unclear. This paper is focused on understanding the PID of crystalline-silicon solar cells and modules. A background for PID, as well as overviews of research on factors accelerating PID, mechanisms involving sodium ions, PID test methods, and possible solutions to the problem of PID, are covered in this paper.

When sunlight irradiates a boron-doped p-type solar cell, the formation of BsO2i decreases the power-conversion efficiency in a phenomenon named light-induced degradation (LID). In this study, we used boron-doped p-type Cz-Si solar cells to monitor this degradation process in relation to irradiation wavelength, intensity and duration of the light source, and investigated the reliability of the LID effects, as well. When halogen light irradiated a substrate, the LID rate increased more rapidly than for irradiation with xenon light. For different intensities of halogen light (e.g., 1 SUN and 0.1 SUN), a lower-limit value of LID showed a similar trend in each case; however, the rate reached at the intensity of 0.1 SUN was three times slower than that at 1 SUN. Open-circuit voltage increased with increasing duration of irradiation because the defect-formation rate of LID was slow. Therefore, we suppose that sufficient time is needed to increase LID defects. After a recovery process to restore the initial value, the lower-limit open-circuit voltage exhibited during the re-degradation process showed a trend similar to that in the first degradation process. We suggest that the proportion of the LID in boron-doped p-type Cz-Si solar cells has high correlation with the normalized defect concentrations (NDC) of BsO2i. This can be calculated using the extracted minority-carrier diffusion-length with internal quantum efficiency (IQE) analysis.