Defect mediated losses and degradation of perovskite solar cells:Origin impacts and reliable characterization techniques

The rapid advancement of halide-based hybrid perovskite materials has garnered significant research attention,particularly in the domain of photovoltaic technology.Owing to their exceptional optoelec-tronic properties,they demonstrated power conversion efficiency(PcE)of over 25%in single junction solar cells.Despite the notable progress in PCE over the past decade,the inherent high defect density pre-senting in perovskite materials gives rise to several loss mechanisms and associated ion migration in per-ovskite solar cells(PsCs)during operational conditions.These factors collectively contribute to a significant stability challenge in PsCs,placing their longevity far behind for commercialization.While numerous reports have explored defects,ion migration,and their impacts on device performance,a com-prehensive correlation between the types of defects and the degradation kinetics of perovskite materials and PsCs has been lacking.In this context,this review aims to provide a comprehensive overview of the origins of defects and ion migration,emphasizing their correlation with the degradation kinetics of per-ovskite materials and PsCs,leveraging reliable characterization techniques.Furthermore,these charac-terization techniques are intended to comprehend loss mechanisms by different passivation approaches to enhance the durability and PCE of PSCs.

Effect of Parameters on Potential Induced Degradation of Solar Cell

Solar cells are widely used to generate electric energy even at homes. It surely has a great advantage of sustainability. However, the potential induced degradation has been found to be an obstacle problem for practical use. It was reported that the main cause is the dielectric breakdown in the glass covered over the solar cells triggered by the thunderstroke. In this paper, the effects of the parameters such as the position of thunderstroke, the wave form, the peak value and the front duration of the lightning current, were examined by means of numerical calculation. For the lightning current, a step-like waveform and an impulse waveform were examined. The effect of the induced voltage was found to be independent of the waveform. The peak value, the front duration of the lightning current greatly affects the induced voltage.

Simulation Suggests Origin of Potential Induced Degradation of Solar Cell

Solar cells are well known as devices for sustainable electric energy generation. Nowadays the potential induced degradation has been brought up as an obstacle problem for practical use. In order to determine the cause of this kind of degradation, numerical simulation by a finite difference time domain method has been performed for computational electromagnetics in the case that the thunder attacks the solar modules. The results show that the dielectric breakdown in the glass covered over the solar cells triggered by the thunderstroke is critical. So it is helpful to protect the dielectric breakdown in the glass from the thunderstroke.

Influence of dye molecular structure on electron transfer in 2,9,16,23-tetracarboxy zinc phthalocyanine sensitized solar cell

2, 9, 16, 23-tetracarboxy zinc phthalocyanine （ZnTCPc） is synthesized and characterized by physicochemical and theoretical methods and it is used as a photosensitizer in dye-sensitized solar cells （DSSC）. The excited lifetime, band gap and frontier orbital distribution of ZnTCPc are investigated by fluorescence spectra, cyclic voltammetry and quantum calculation. The results show that the excited lifetime and band gap are 0. 1 ns and 1.81 eV, respectively. Moreover, it is found that the highest occupied molecular orbital （HOMO） location is not shared by both the zinc metal and the isoindoline ligands, and the lowest unoccupied molecular orbital（LUMO） location does not strengthen the interaction coupling between ZnTCPc and TiO：. As a result, the ZnTCPc-DSSC gains a short-circuit current density of 0. 147 mA/cm2, an open-circuit photovoltage of 277 mV, a fill factor of 0. 51 and an overall conversion efficiency of 0. 021%.

Stabilizing perovskite precursors with the reductive natural amino acid for printable mesoscopic perovskite solar cells

Solution processability significantly advances the development of highly-efficient perovskite solar cells.However,the precursor solution tends to undergo irreversible degradation reactions,impairing the device performance and reproducibility.Here,we utilize a reductive natural amino acid,Nacetylcysteine(NALC),to stabilize the precursor solution for printable carbon-based hole-conductorfree mesoscopic perovskite solar cells.We find that I_(2) can be generated in the aged solution containing methylammonium iodide(MI) in an inert atmosphere and speed up the MA-FA^(+)(formamidinium) reaction which produces large-size cations and hinders the formation of perovskite phase.NALC effectively stabilizes the precursor via its sulfhydryl group which reduces I_(2) back to I^(-)and provides H^(+).The NALC-stabilized precursor which is aged for 1440 h leads to devices with a power conversion efficiency equivalent to 98% of that for devices prepared with the fresh precursor.Furthermore,NALC improves the device power conversion efficiency from 16.16% to 18.41% along with enhanced stability under atmospheric conditions by modifying grain boundaries in perovskite films and reducing associated defects.

Improving the stability of metal halide perovskite solar cells from material to structure

Metal halide perovskites(MHPs) are promising photovoltaic(PV) materials owing to their advantages such as high carrier mobility, excellent absorption coefficient, bandgap tenability, long diffusion length,and low material cost. These qualities have increased the efficiency of MHP solar cells to 23.3%. However,MHPs are hindered by a lack of stability. In addition, the applications of MHP solar cells are restricted by the instability of perovskite materials and devices. In this article, the most urgent stability problems faced by perovskite solar cells are identified, and recent progresses in MHPs are enumerated. The factors affecting the stability of perovskite materials and devices are also discussed. We analyzed the thermal and humid stability of perovskite materials in terms of transporting materials and their interface. In view of these recent advances, future works should focus on the large-scale application of MHP solar cells.

Spatial Distribution of Radiation Belt Protons Deduced from Solar Cell Degradation of the Arase Satellite

Analysis of solar-cell array panel (SAP) data from the Arase satellite orbiting in the inner magnetosphere showed a clear degradation of solar cells that could be attributed to trapped protons with energies greater than 6 MeV. Proton fluence was determined based on variations in the open-circuit voltage (Voc) of the solar cells, which we compared with that expected based on various distribution models (AP8MAX, AP9 mean and CRRESPRO quiet) of trapped protons. We found a general agreement, confirming the major contribution of trapped protons to the degradation, as well as a slight difference in the fluence expected based on the model calculations. To minimize this difference, we slightly modified the models, and found that concentrating the energetic protons on the magnetic equator provided a better agreement. Our results indicate that >6 MeV protons also has the equatorial concentration as reported for >18 MeV protons from the Van Allen Probes observation, and are interpreted as two components of the trapped protons, i.e., those of solar energetic particle (SEP) origin have an anisotropic pitch-angle distribution and are confined near the magnetic equator.

Variation of Quantum Efficiency in CZTSSe Solar Cells with Temperature and Bias Dependence by SCAPS Simulation

The quantum efficiency of CZTSSe （copper zinc tin sulphur selenium） thin film solar cells is numerically simulated at different temperatures and under a set of bias conditions about the efficiency limiting factors. A systematic methodology is developed and integrated into the proposed model to simulate the characteristics in the quantum efficiency. The proposed model is demonstrated with respect to an ideal device model under a set of bias conditions to selectively deactivate performance limiting parameters under light and voltage biased conditions. Under particular wavelength regions and bias conditions, a particular type of defects near the heterojunction interface significantly impact the carrier collection of devices. This deep acceptor type defect distribution is located in the band of ＋/- 0.3 eV from the midgap. These defect states influence CZTSSe spectral responses of red and IR light wavelength regions in quantum efficiency caused by affected depletion width toward the back contact. Therefore, the quantum efficiency of CZTSSe devices is altered disproportionally at biased conditions.

Review on Chemical Stability of Lead Halide Perovskite Solar Cells

Lead halide perovskite solar cells(PSCs) have become a promising next-generation photovoltaic technology due to their skyrocketed power conversion efficiency. However, the device stability issues may restrict their commercial applications, which are dominated by various chemical reactions of perovskite layers. Hence, a comprehensive illustration on the stability of perovskite films in PSCs is urgently needed. In this review article, chemical reactions of perovskite films under different environmental conditions(e.g., moisture,oxygen, light) and with charge transfer materials and metal electrodes are systematically elucidated. Effective strategies for suppressing the degradation reactions of perovskites, such as buffer layer introduction and additives engineering,are specified. Finally, conclusions and outlooks for this field are proposed. The comprehensive review will provide a guideline on the material engineering and device design for PSCs.

Conductivity Degradation Study of PEDOT: PSS Films under Heat Treatment in Helium and Atmospheric Air

PEDOT:PSS buffer layers have been processed with the standard annealing step used for organic solar cells device applications. The d.c. conductivity σ as a function of temperature for two heating rates under He and atmospheric air was studied. Moreover, the stability of the conductivity was investigated at different temperatures and environments vs time. The main results can be summarized in the following: the increase of σ due to the thermal activation of the carriers and the improvement of the crystallinity compete with the decrease of σ resulting from the irreversible structural degradation of the polymer chains promoted by the oxygen and moisture of the atmospheric air. The heat treatment time and the temperature at which the two competing mechanisms result in a maximum of the electrical conductivity have been determined and results are discussed relevant to organic optoelectronic devices containing PEDOT: PSS buffer layers.

Unveiling the key factor affecting the illumination deterioration and response measures for lead halide perovskite solar cells

So far,it's been widely acknowledged that the Pb I2decomposition under illumination mainly accounts for the degradation of perovskite solar cells(PSCs)under maximum power point(MPP)tracking condition.However,PSCs without excess Pb I2were also reported to deteriorate rapidly under the same condition.Here,we demonstrate that the key to enhance PSCs stability under MPP tracking condition is not to have fascinating surface morphology with effective suppression of nonradiative recombination traps but to prevent the migration of iodine ion(I-)under light illumination.By partially substituting methylammonium chloride(MACl)with methylammonium iodide(MAI)and simutaneouly introducing I2during the sequential deposition,the iodine vacancies in perovskite films are substantially suppressed,thereby limiting the pathways for I^(-)migration.As a consequence,PSCs with efficiency of 24.28%are fabricated with remarkably enhanced working stability.

In situ Investigations of Interfacial Degradation and Ion Migration at CH3NH3PbI3 Perovskite/Ag Interfaces

Interfacial properties between perovskite layers and metal electrodes play a crucial role in the device performance and the long-term stability of perovskite solar cells.Here,we report a comprehensive study of the interfacial degradation and ion migration at the interface between CH3NH3PbI3 perovskite layer and Ag electrode.Using in situ photoemission spectroscopy measurements,we found that the Ag electrode could induce the degradation of perovskite layers,leading to the formation of PbI2 and AgI species and the reduction of Pb^2+ions to metallic Pb species at the interface.The unconventional enhancement of the intensities of I 3d spectra provides direct experimental evidences for the migration of iodide ions from CH3NH3PbI3 subsurface to Ag electrode.Moreover,the contact of Ag electrode and perovskite layers induces an interfacial dipole of 0.3 eV at CH3NH3PbI3/Ag interfaces,which may further facilitate iodide ion diffusion,resulting in the decomposition of perovskite layers and the corrosion of Ag electrode.

Gradual Band Energy to Passivate the Window Layer in Solar Cells

The passivation layers at the front of the cell are often referred as to the window layer because it must be transparent so as the solar cell has a high efficiency. In this work, numerical simulation has been proposed to study the effect of the AlGaAs gradual and normal windows on the cell sensitivity to the electron irradiation so as to passivate the solar cell. To expect the effect of gradual window layers, the J-V and P-V characteristics are confirmed better energy conversion performance of the illuminated solar cells after irradiation. The short circuit current Jsc and the open circuit voltage Voc are evaluated for different electron irradiation fluencies. The results show how the gradual window layer improves resistance to electron irradiation through its own parameters.

Theoretical Studies on Structural and Spectroscopic Properties of Photoelectrochemical Cell Ruthenium Sensitizers―the Derivatives of N3

A series of dye molecules was designed theoretically.Particularly,azoles and their derivatives were chosen as the modifying groups linking to ancillary ligands of [Ru（dcbpyH2）2（NCS）2]（N3,dcbpy=4,4＇-dicarboxy2,2＇-bipyridine;NCS=thiocyanato）.Density functional theory（DFT） based approaches were applied to exploring the electronic structures and properties of all these systems.The dye molecule with 1,2,4-triazole groups which exhibits a very high intensity of absorption in visible region,was obtained.Time-dependent DFT（TD-DFT） results indicate that the ancillary ligand dominates the molecular orbital（MO） energy levels and masters the absorption transition nature to a certain extent.The deprotonation of anchoring ligand not only affects the frontier MO energy levels but also controls the energy gaps of the highest occupied MO（HOMO） to the lowest unoccupied MO（LUMO） and LUMO to LUMO＋1 orbital.If the gap between LUMO-LUMO＋1 is small enough,the higher efficiency of dye-sensitized solar cell（DSSC） should be expected.

An industrial solution to light-induced degradation of crystalline silicon solar cells

Boron-oxygen defects can cause serious lightinduced degradation （LID） of commercial solar cells based on the boron-doped crystalline silicon （c-Si）, which are formed under the injection of excess carriers induced either by illumination or applying forward bias. In this contribution, we have demonstrated that the passivation process of boron-oxygen defects can be induced by applying forward bias for a large quantity of solar cells, which is much more economic than light illumination. We have used this strategy to trigger the passivation process of batches of aluminum back surface field （A1-BSF） solar cells and passivated emitter and rear contact （PERC） solar cells. Both kinds of the treated solar cells show high stability in efficiency and suffer from very little LID under further illumination at room temperature. This technology is of significance for the suppression of LID of c-Si solar cells for the industrial manufacture.

Preparation of Perovskite Solar Cells in the Air:Degradation Mechanism and Prospects on Large-Area Fabrication

The preparation of perovskite solar cells(PsCs)in the air environment has attracted the attention of numerous experimenters due to its low preparation cost and the possibility of commercialization.Although the power conversion efficiency(PCE)of PSCs has increased rapidly and exceeded 25%,which is comparable to commercial polysilicon solar cells,most certified or reported high-efficiency perovskite solar cells are still confined to glove boxes or relatively small active areas in the air environment due to moisture,oxygen,high temperature,and ultraviolet(UV)factors.In this review.

Degradation mechanism and stability improvement of formamidine-based perovskite solar cells under high humidity conditions

Formamidine(FA)-based perovskite solar cells(PSCs)are promising candidates for photoelectric conversion devices due to their excellent optoelectronic properties.However,the instability of perovskites,especially moisture instability,remains one of the biggest obstacles to the commercialization of perovskite devices.Therefore,it is very important to explore and target the effect of moisture on FA-based perovskites to prevent this effect and improve device stability.Herein,we studied the degradation process of commonly used FA-based perovskite films by X-ray diffraction and scanning electron microscopy characterization and analyzed the reasons for their humidity-induced degradation.Subsequently,we further adopted a strategy by adding methylammonium bromine powder into a PbI_(2) precursor solution to prepare a seed solution in a two-step preparation process to enhance the performance and stability of FA-based PSCs.Finally,the degradation rate of the obtained perovskite film was significantly slowed down under high humidity compared to that of perovskite films prepared by a two-step method without applying a seed solution.The corresponding device achieved a remarkable power conversion efficiency of 23.22%,and the efficiency of this device showed no attenuation after 900 h of exposure to air.

Evaluating electron induced degradation of triple-junction solar cell by numerical simulation

In this paper,the degradation related parameters of GaInP/GaAs/Ge triple-junction solar cell induced by electron irradiation are carried out by numerical simulation.The degradation results of short-circuit current,open-circuit voltage,maximum power have been investigated,and the degradation mechanism is analyzed.Combining the degradation results,the degradation of normalized parameters versus displacement damage dose is obtained.The results show that the degradation increases with the increase of the electron fluence and electron irradiation energy.The degradation normalized related parameters versus displacement damage dose can be characterized by a special curve that is not affected by the type of irradiated particles.By calculating the annual displacement damage dose and the on-orbit operation time of special space orbit,the degradation of normalized parameters can be obtained with the fitting curve in the simulation.The study will provide an approach to estimate the radiation damage of triple-junction solar cell induced by space particle irradiation.

Impeded degradation of perovskite solar cells via the dual interfacial modification of siloxane

It is challenging to improve the long-term stability of perovskite solar cells(PSCs) without sacrificing efficiency. The perovskite absorbers degrade from the film surface/interfaces, which follows entangled mechanisms that have not been fully revealed yet.Herein, we decouple and elaborate two distinctive pathways regarding film degradation based on FACsPbI3perovskites.Moreover, a dual interfacial modification strategy has been developed for improving the material’s intrinsic stability, thus leading to the film degrading in a more retardant pathway. The corresponding PSCs achieve a stable power output efficiency of 23.75%.More importantly, the unencapsulated PSCs devices retain over 93% of their initial PCE after the maximum power point(MPP)tracking under the continuous 1-sun illumination and show significantly improved stability after aged under the thermal treatment or stored in ambient atmosphere for over 1500 hours without obvious PCE decay. This work shows the importance of modulating the degradation pathway on stability improvement, and at the same time, proposes a strategy for designing perovskite-based optoelectronics with excellent performance and stability.

等效位移损伤剂量法预测GaInP2/GaAs/Ge三结电池在轨性能退化规律

文章首先在辐照条件下测试GaInP2/GaAs/Ge三结太阳电池的光谱响应,确定了三结电池在轨道带电粒子辐照条件下的损伤特征。通过试验获得了在不同粒子辐照条件下电池电性能退化规律,由此确定了高能电子与质子辐照对三结电池损伤的等效参数,建立了三结电池最大输出功率随位移损伤剂量的退化方程。在此基础上,以地球同步轨道服役的太阳电池为例,计算了电池在轨等效位移损伤剂量,并对三结电池的在轨服役行为进行了评价。