Cu(In,Ga)Se2 (CIGSe) solar cells have rapidly advanced over the past decade; however, achieving robust longterm stability is a crucial issue that needs to be solved for their commercial success. Due to the heavy weight and rigid limitation of traditional glass cover, the long-term reliability of photovoltaic modules employing nonglass cover materials is still being developed and investigated. This study comprehensively evaluates a highbarrier flexible encapsulation scheme under extended damp heat (DH) testing. Two CIGSe mini-modules underwent a 3600-hour test, with one was continuously biased near its voltage at the maximum power point (Vmpp) and the other was left under unbiased conditions. Remarkably, both mini-modules exceed the IEC 612152 standards, maintaining over 97 % of their efficiencies after over 3000 h of the DH test. Furthermore, the impact of the continuous electrical operation during the DH test is also investigated. The mini-module under Vmpp bias sustained high performance during prolonged DH exposure, but interruption of the bias voltage led to an efficiency decline, which can be reversible. This observation suggests the potential for bias-driven stabilization mechanisms at the material or interface level, necessitating further in-depth investigation to optimize operational protocols for enhanced long-term reliability of flexible CIGSe solar cells in DH environments. The effectiveness of the demonstrated encapsulation strategy provides a significant step toward realizing the full potential of flexible CIGSe technology.

Cu(In,Ga)Se2 (CIGSe) thin-film solar cells, known for their high efficiency and flexibility, are rapidly used in a variety of applications. Glass top cover encapsulation is a widely recognized method for protecting solar cells from moisture, oxygen, and mechanical stress. However, this approach increases the module's weight, and the rigidity of glass also limits the flexibility of the modules. This study investigates the long-term stability and performance of encapsulated CIGSe cells under the damp heat (DH) test as specified in the IEC 61215-2 standard. The CIGSe device was encapsulated with a lamination-based encapsulation structure using a high-barrier flexible polyethylene terephthalate (PET) front sheet and exposed to 85oC/85% relative humidity (RH), which was carried out for 2448h. The effectiveness of forward bias voltage during the DH test was investigated by comparing two groups of cells: one group was connected with bias voltage at voltage maximum power point (Vmpp) value, and another was kept under open-circuit condition. Under both conditions, CIGSe solar cells passed the standard test by maintaining over 95% of their initial efficiency after 1000h of DH test, demonstrating the effectiveness of the encapsulation method that facilitates prolonged environmental stress. The cells with a forward bias voltage applied retained higher efficiencies with 99% and 98% of their initial efficiencies after 1008h and 2448h of the DH test, respectively. These results provide substantial information for building durable photovoltaic modules capable of withstanding harsh climatic conditions, thereby contributing to the advancement of sustainable solar energy technologies.

The understanding of moisture-induced degradation is one of the major issues towards long-term stability of perovskite solar cells (PSCs) which severely limit their practical use. Herein, the degradation behavior of photovoltaic performance on water ingress of flexible methylammonium lead halide (MAPbI3) PSC mini-modules with 3 x 3 cm2 in size was discussed. For this purpose, the modules proceed the damp-heat (DH) test up to 4650 h at 85 degrees C/85 % relative humidity and water ingress was systematically controlled by varying water vapor transmission rates (WVTRs) of the barrier film from 0.005 to 0.44 g/m2/day. Upon DH testing, the evolution of solar cell parameters revealed that the power conversion efficiency (PCE) was gradually reduced over DH time. Remarkably, encapsulation with barrier films of high WVTRs (0.019-0.44 g/m2/day) caused 'critical failure' of module efficiency, evidently observed at the same level of accumulated water vapor. The phase decomposition emphasized that the critical failure mainly stemmed from the partial formation of intermediate MAPbI3 monohydrate due to the water vapor permeated into encapsulated module, particularly in cases with high WVTRs. This hydrate intermediate accelerated the perovskite decomposition and suddenly reduced its module lifetime. On the other hand, the module encapsulated using a proper barrier film with low WVTR of 0.005 g/m2/day exhibited outstanding module stability by nearly 80 % of PCE upon 2700 h of DH test and no critical failure. This finding demonstrated significant improvement in module durability through the selection of barrier films, thereby extending the device lifetime and enhancing its long-term suitability for the potential application in photovoltaic industry.

Half-cell photovoltaic modules reduce resistive losses but can exhibit hotspot mirroring under partial shading, where an unshaded cell in the parallel-connected mirror substring dissipates power when the bypass diode conducts. We present outdoor infrared thermography of a 120-half-cell silicon heterojunction (SHJ) module at fixed high- and low-voltage operating points: pronounced heating appears in an unshaded mirror cell at the low-voltage point with bypass activation, whereas no pronounced heating is observed at the high-voltage point without bypass activation. To clarify the circuit origin and triggering conditions, we developed a SPICE-based equivalent-circuit model parameterized from an encapsulated SHJ coupon cell. The model reproduces the measured I–V characteristics and shows that bypass activation imposes a small negative voltage across the diode-protected parallel-substring unit (i.e., the two parallel substrings protected by one bypass diode). Simulations with realistic cell-to-cell variability reveal that a slight short-circuit-current mismatch (ΔIsc) can drive a mirror cell into strong reverse bias and localize dissipation, while a parametric study indicates ΔIsc dominates dissipated power and shunt-resistance variations are secondary. These results provide outdoor-validated, circuit-level guidance for mitigating hotspots in half-cell modules beyond shaded-cell-only evaluation.

Precise and quick performance measurement and power rating of Perovskite photovoltaic devices such as Perovskite solar cells (PSCs) and modules (PSC modules) are essential for their industrialization. A major issue of their performance measurement is their gradual performance change under light soaking, which necessitates preconditioning by light soaking prior to measuring their stabilized performance such as the I-V curves. The present study investigated the preconditioning of flexible PSC modules. It was shown that application of forward bias voltage to the PSC modules in the dark for a short time of typically <10 min. improves the performance of the modules such as the maximum output power Pmax, which is virtually the same effect as the light soaking. When a forward bias voltage was applied in the dark, increase in the performance parameters such as the maximum output power Pmax was observed. It was found that the magnitude and rate of the increase were nearly the same as those of the light soaking at 1 kW/m(2), when the forward bias voltage equal to the open circuit voltage V-oc at the same irradiance was applied in the dark. The present results clarified that preconditioning without light soaking is possible, and showed that the photo-generate voltage rather than the light itself plays an important role in the increase in Pmax by the light soaking. It also offered the possibility to improve the productivity of the performance measurement of PSC modules.

The stability of flexible perovskite solar cell (PSC) modules based on methylammonium lead iodide (CH3NH3PbI3 or MAPbI3) was studied under damp heat (DH) stress test using barrier films with different level of water vapor transmission rates (WVTR) in the range of 5.0 x 10-3 and 7.4 x 10- 1 g/m2/day measured at 85 degrees C. For this purpose, PSC modules were subjected to 2000 h DH-test (85 degrees C, 85 % relative humidity, RH). The photovoltaic (PV) performance of the modules showed different rates of degradation, which increased with increasing the WVTR value. For higher WVTR values, I-V curves depicted the 2nd diode component. Analysis of surface reflectance spectra and electroluminescence data confirmed the acceleration of degradation with increased WVTR value, which was expected to chemical decomposition of perovskite, and segregation of PbI2 at the interface acting as a hole-blocking layer. At 1000 h (2000 h) DH-test, the sample with lowest WVTR retained its 91.5 % (84.2 %) power conversion efficiency, i.e., mainly resulting from short-circuit current loss of -8% (-10 %). It has been shown that there is a threshold WVTR value to suppress the water vapor integration. Ultimately, this study highlights the importance of barrier film quality towards maintaining the long-term stability of PSC modules.

Structural and morphological properties were studied via destructive measurements after damp-heat test (DHT) on flexible perovskite solar cell modules with a device structure of "front polyethylene terephthalate (PET) with barrier layer/encapsulant/PET/In2O3:Sn (ITO)/compact-TiO2/mesoporous-TiO2/MAPbI3/Spiro-OMeTAD/metal electrode/encapsulant/back PET with Al layer". Solar cell parameters tend to decrease with increasing the DHT duration and water vapor transmission rate of the barrier film, whereas "S-shape" developed in current-voltage curves that is an indication for the presence of second diode component in the device structure. After 2000h DHT, back PET film with aluminum layer, metal-electrode layer, and Spiro-OMeTAD layer were peeled off in sequence to study the structural and morphological properties of perovskite layer. Moreover, numerical simulations were carried out to understand the degradation mechanisms through the utilization of one-dimensional SCAPS device simulation software. Overall, the formation of PbI2, which segregated in plane, was suggested to be the main degradation mechanism under DHT, possibly acting as a second diode component in the cells. Since the formation of PbI2 is mainly triggered by water/humidity, it can be minimized or even suppressed by improving the quality of barrier film.

Stability of flexible perovskite solar cell (PSC) modules have been investigated in heat test and damp-heat test (DH-test) conditions. Heat-tests were performed at 85, 95, and 105 degrees C, while DH-test were at 85 degrees C/85 % relative humidity (RH), 95 degrees C/85%RH, and 99 degrees C/85%RH. For this purpose, the devices with a standard structure of "polyethylene terephthalate (PET)/Sn-doped In2O3/compact-TiO2/mesoporous-TiO2/CH3NH3PbI3/Spiro-OMeTAD/metal electrode" were fabricated. Consequently, the PSC modules were encapsulated by sandwiching front PET film with a barrier layer and back PET film with aluminum layer. Although the perovskite layer can be readily decomposed even at room temperature in the presence of water, it has been shown that devices' stability can be significantly enhanced by proper encapsulation. In particular, the properties of the barrier film such as water vapor transmission rate play a crucial role to suppress the ingress and integration of water/humidity into the device. As expected, PSC modules showed better stability under heat-test over DH-test. However, damp-heat stability significantly improved for the samples with lower WVTRs. The flexible PSC module with WVTR of 0.005 g/m2/day showed improved stability in DH-test, which showed no critical failure, i.e., sudden degradation of solar cell parameters, even after 4200h of DH-test under 85 degrees C/85%RH.

This study aims to clarify the process of oral drug absorption from jelly formulations. Agar and pectin-based jellies containing drugs with different membrane permeability (high: antipyrine [ANT], medium: metoprolol [MET], low: atenolol [ATE]) were prepared and tested for in vitro drug release and in vivo drug absorption in rats. All drugs showed similar release profiles in vitro from both jelly formulations, except for the faster release from pectin jelly at neutral pH. In contrast, in vivo absorption of ATE but not of ANT from jelly formulations was significantly lower than from solution. Absorption of ATE and MET was low from agar jelly after oral administration, whereas additional water intake significantly increased the absorption. The process of drug absorption was described by the compartmental model consisting of jelly, intestinal fluid, and blood compartments. Drugs in the jelly diffuse into the intestinal fluid and then permeate the intestinal membrane. By considering the rate-limiting process, membrane permeability-dependent drug absorption from agar jelly and the effects of water intake were identified. In conclusion, jelly formulations may potentially decrease and delay drug oral absorption, especially of poorly permeable drugs. Intestinal fluid volume is one of the important factors to control the drug absorption.

The stability of methylammonium lead iodide (MAPbI )-based flexible perovskite (PVK) mini modules was studied under thermal stress. For this purpose, PVK mini modules, consisting of 10 serially connected cells with an aperture area of 9 cm , were subjected to elevated temperatures of 85℃, 95℃, and 105℃ for 4000 h. The photovoltaic (PV) parameters of PVK mini modules were periodically measured by interrupting the thermal stress tests. Evolution of series resistance, short circuit current, and fill factor showed monotonic reduction, whereas shunt resistance and open circuit voltage depicted three stage degradation: (i) initial rapid degradation; (ii) quasi stable range; and (iii) gradual monotonic degradation stages, which are the indication for the presence of several degradation mechanisms. Using the experimental data, activation energy ( E) of degradation was studied by adopting the Arrhenius model. E of 1.062 eV (102.5 kJ/mol) was obtained for the maximum output of the total device. Device lifetime, which is defined as the point where the efficiency has reduced to 80% of its initial value, 30.6 years was estimated, i.e., performance loss of around 0.65% per year, at module temperature of 45℃.

The thermal stability of methylammonium lead iodide (MAPbI(3))-based flexible perovskite solar cell (PSC) modules was studied. For this purpose, PSC modules, consisting of 10 serially connected cells with an aperture area of 9 cm(2), were heated at 85 degrees C, 95 degrees C, and 105 degrees C for 4000 h. The solar cell parameters were periodically measured by interrupting the thermal stability tests. Evolution of series resistance, short circuit current, and fill factor showed monotonic reduction, whereas shunt resistance and open circuit voltage depicted three stage degradation: (i) initial rapid degradation; (ii) quasi stable range; and (iii) gradual monotonic degradation stages, which are the indication for the presence of several degradation mechanisms. Using the Arrhenius model, activation energy (E-a) of degradation was studied. E-a of 1.062 eV (102.5 kJ/mol) was obtained for the maximum output of the total device. Device lifetime for thermal stability, which is defined as the point where the efficiency has reduced to 80 % of its initial value, was also estimated at module temperature of 45 degrees C.

Improvement of the quantitative performance characterization of photovoltaic (PV) strings was investigated, based on their monitoring data during maximum power point tracking (MPPT) operation. The maximum power voltage V-mp and current I-mp of the PV strings under MPPT were continuously monitored, and corrected to standard temperature of 25 degrees C by using the temperature correction formulas, which were recently developed for PV modules. The irradiance G was measured by using a PV module irradiance sensor. It was verified that the formulas are applicable to PV strings, enabling reproducible temperature correction of V-mp and I-mp with relative standard deviation (sigma) of about 0.4-0.9% under various weather conditions. Comparison of the outdoor results with indoor current-voltage curve measurements of the constituent modules in the strings showed that the maximum output power P-max under the standard test conditions STC, i.e. 25 degrees C and 1 kWm(-2), estimated from the temperature-corrected V-mp and I-mp, agreed with the indoor result typically within +/- 1.5%. The experimental results also showed that other information of the string such as partial shading and activation of bypass diodes can be also sensitively detected by analyzing the temperature-corrected V-mp and I-mp. The outdoor measurements and data analysis of this study can be carried out without stopping the MPPT operation of the string. The analysis is performed by using the real-time data. The present method is expected to be applicable to most kinds of crystalline silicon PV strings without modification.

Various types of degradations and failures occur in photovoltaic (PV) modules during their outdoor operation, such as cell cracks and an increase in series resistance.Sensitive detection of them is essential to improve the efficiency and reliability of the PV modules and systems.Previous detection techniques such as the I-V curve measurement had a problem because they needed to interrupt the maximum power point tracking (MPPT) operation of the PV system.This study proposes a new method to detect those degradations and failures without interrupting the MPPT operation by using the time-series data of the voltage and current at the maximum power point (V mp and I mp , respectively).The V mp and I mp are corrected for temperature using recently developed temperature correction formulas, and are analyzed as the I mp -V mp curves.It is shown that the existence of a cracked cell in a PV module can be sensitively detected from the I mp -V mp curve, since the decrease in the photocurrent of a cracked cell tends to shift a part of the I mp -V mp curve of the module toward high voltage.The experimental and simulation results indicate that a small cell crack less than 10% of a cell area can be detected.In addition, the simulation results also reveal that the increase in series resistance can be detected by the distortion of the I mp -V mp curve toward a lower voltage in the high I mp , or high irradiance, region.These simulation results indicate that the present method is very powerful for detecting the degradation and failure of PV modules and systems.

Spectral mismatch correction factor (MM) is determined by average photon energy (APE). APE based on wide solar spectral ranges leads to better description of solar spectral shape. Moreover, error between corrected outdoor short-circuit current (ISC) of PV module and its ISC under standard test conditions is investigated using PV module irradiance sensor (PVMS) and/or MM, where PVMS is a single-crystalline silicon PV module. The error of muti-crystalline silicon (mc-Si) PV module is as low as about 1% regardless of the use of MM attributed to small spectral mismatch between PVMS and mc-Si PV module. On the other hand, the low error of CdTe test PV module is obtained under the use of both PVMS and MM caused by the high spectral mismatch between PVMS and CdTe test PV module. The error is further decreased, when MM is estimated from the APE based on wide ranges of the solar spectrum.

Spectral gain and loss (spectral gain&loss) of different-type photovoltaic (PV) modules, which are (1) amorphous silicon (a-Si), (2) perovskite (PVK), (3) CdTe, (4) CuInSe2, (5) multi-crystalline silicon, (6) single-crystalline silicon back-contact, and (7) heterostructure-with-intrinsic-thin-layer PV modules, is examined at different locations (Naganuma, Tsukuba, Gifu, Tosu, and Okinoerabu cities in Japan). Reference single-crystalline (sc-Si) PV module is utilized. It is revealed that average photon energy (APE) is uniquely used as an index of solar spectral irradiance regardless of outdoor sites, where APE of 1.59 eV represents airmass 1.5G spectrum with wavelength range from 350 nm to 1700 nm. APE is varied, depending on locations and seasons in a year, and it is the highest of over 1.59 eV (or blue-rich spectra) in summer. Average APE values in four-year period are 1.623 eV, 1.612 eV, 1.618 eV, 1.621 eV, and 1.652 eV at Naganuma, Tsukuba, Gifu, Tosu, and Okinoerabu cities, respectively, representing blue-rich spectra. Ultimately, spectral grain&loss of a-Si, PVK, and CdTe PV modules is above 1 (spectral gain) at investigated locations, implying that appropriate a-Si, PVK, and CdTe PV technologies with large bandgap outperform reference sc-Si PV technology in term of spectral response. Spectral grain&loss with different seasons is additionally discussed.

Outdoor performance of test photovoltaic (PV) modules, especially short circuit current (I-SC), is corrected to standard test conditions (STC) utilizing sc-Si PV module as PV module irradiance sensor (PVMS). In this contribution, average photon energy (APE) can be used as an index of solar spectral irradiance. The CdTe PV module was used as a test PV module since its spectrum response is significantly different from that of the PVMS to investigate an effect of spectral mismatch. The median of the error between I-SC corrected to STC (ISC-correction) of CdTe PV module using PVMS and its I-SC under STC is the highest at 2.64% under APE from 1.75 to 2.15 eV because of the spectral mismatch between PVMS and test PV module. On the other hand, the median of the error is obviously reduced to 0.89%, when ISC-correction was estimated using PVMS and spectral mismatch correction factor under APE from 1.75 to 2.15 eV. The lowest median of 0.54% for the error is furthermore realized under APE in a range of 1.83-1.95 eV, where spectral irradiance mostly indexed by the APE range from 1.83 to 1.95 eV (83% of all spectral irradiance) is frequently occurred at the outdoor installation site. (C) 2020 Elsevier Ltd. All rights reserved.

Estimation of the performance of photovoltaic (PV) module and system by using continuous monitoring data is an important issue, since the output power of PV modules is changeable, affected by the irradiance, temperature and shading effect, as well as degradation. This work proposes a method to detect partial shading on a module during its maximum power point tracking (MPPT) operation. It identifies whether there is shading on a module or not by analyzing data of the voltage at maximum power (V-mp) and the current at maximum power (I-mp). Recently developed temperature correction formulas for the Vmp and Imp are used, in order to analyze them under various temperatures and irradiances. The experimental and simulation results show that the shading effect usually results in larger Vmp than the shadeless case, compared at the same Imp. Therefore, the Imp Vmp curve shifts toward higher voltages by the shading effect, thereby enabling detection of the existence of the shading effect. A method to identify the shading effects on a PV module from the I-mp - V-mp curve has been clarified, which does not require I-V curve measurements. Slight partial shading such as a drop in the photocurrent of a single cell in a module by about 5-10% is possibly detected. The present results are also applicable to PV systems that include multiple modules. They are expected to be useful for accurately monitoring the performance of PV modules and systems under operation, since the Vmp and Imp are measurable without breaking the MPPT operation.

Short-circuit current (I-SC) values of test photovoltaic (PV) modules, i.e., multi-crystalline silicon, heterostructure-with-intrinsic-thin-layer, single-crystalline silicon back-contact, CulnSe(2) (CIS), and CdTe modules, are descripted using multiple regression analysis based on environmental factors (solar irradiance, average photon energy (APE), and module temperature (T-mod)) under several solar irradiance levels. The APE is an index of the solar spectral irradiance distribution. PV module irradiance sensor (PVMS), single-crystalline silicon PV module, is used to investigate simultaneous solar irradiance (IrrT(PVMS)). It is disclosed that I-SC is primarily determined by IrrT(PVMS). Error between the estimated I(SC )and measured I(SC )of test PV modules is investigated. Consequently, precise I(SC )description (low error) is obtained when IrrT(PVMS) is utilized. The more precise description of the I(SC )for CIS and CdTe PV modules, having the bandgap (E-g) different from PVMS, is realized when adding APE environment factor even under low IrrT(PVMS) (>= 0 kW/m(2)), accumulated on both sunny day and cloudy day suggesting the enhancement of investigation opportunity. This is because APE minimizes spectral mismatch error caused by E-g difference between PVMS and test PV module. Moreover, the precision of I-SC description is further increased under enhanced IrrT(PVMS) of >= 0.5 kW/m(2) (on sunny day) due to stable solar irradiance. (C) 2019 Elsevier Ltd. All rights reserved.

Spectral grain and loss (spectral gain&loss) of several-type PV technologies (amorphous silicon (a-Si), perovskite (perov), CdTe, CuInSe2 (CIS), multi-crystalline silicon (mc-Si), single-crystalline silicon back-contact (BC), single-crystalline silicon (sc-Si), and heterostructure-with-intrinsic-thin-layer (HIT)) was investigated in different places (Kusatsu city, Tsukuba city, and Miyazaki city in Japan) in a year. Spectral gain&loss is defined as a ratio of short-circuit current (I-SC) corrected by solar irradiance (Irr) for PV module at an average photon energy (APE) to its I-SC under standard test condition. The blue-rich spectra with APE over 1.88 eV yield spectral gain (spectral gain&loss over 1) for CdTe, perov, and a-Si PV technologies owing to large band-gap energy (E-g) values of 1.47, 1.60, and 1.80 eV, respectively. On the other hand, red-rich spectra with APE below 1.88 eV lead to spectral gain for CIS, me-Si, BC, sc-Si, and HIT PV technologies with smaller E-g values of 1.21, 1.13, 1.17, 1.16, and 1.09 eV, respectively. Moreover, since average APE values in Kusatsu city, Tsukuba city, and Miyazaki city are 1.931, 1.900, and 1.899 eV, respectively, a-Si, perov, and CdTe PV technologies are suitable in term of spectral response. The spectral gain&loss of PV modules compared with sc-Si PV module is moreover discussed. (C) 2019 Elsevier Ltd. All rights reserved.