Search Results (17)

Flexibility, light weight, and mechanical robustness are the key advantages of flexible photovoltaic (PV) modules, making them highly versatile for sustainable energy solutions. Unlike traditional rigid PV modules, their flexible nature makes them incredibly versatile for harnessing energy in places where doing so was once impossible. They have a wide range of applications due to their flexibility and moldability, making it possible to conform these modules to surfaces like curved rooftops and other irregular structures. In this paper, we provide a comprehensive review of all the materials used in flexible PV modules with a focus on their role in sustainability. We thoroughly discuss the active-layer materials for crystalline silicon (c-Si)-based solar cells (SC) and thin-film solar cells such as cadmium telluride (CdTe), as well as copper indium gallium diselenide (CIGS), amorphous thin-film silicon (a-Si), perovskite and organic solar cells. Various properties, such as the optical, barrier, thermal, and mechanical properties of different substrate materials, are reviewed. Transport layers and conductive electrode materials are discussed with a focus on emerging trends and contributions to sustainable PV technology. Various fabrication techniques involved in making flexible PV modules, along with advantages, disadvantages, and future trends, are highlighted in the paper. The commercialization of flexible PV is also discussed, which is a crucial milestone in advancing and adapting new technologies in the PV industry with a focus on contributing toward sustainability. Full article

Organic–inorganic hybrid metal halide perovskites are poised to revolutionize the next generation of photovoltaics with their exceptional optoelectronic properties and compatibility with low-cost and large-scale fabrication methods. Since perovskite tends to degrade over short time intervals due to various parameters (oxygen, humidity, light, and temperature), advanced characterization methods are needed to understand their degradation mechanisms. In this context, investigation of the electrical and optoelectronic properties of several perovskite mini-modules was performed by means of photo- and electroluminescence imaging as well as Dark Lock-In Thermography methods. Current–voltage curves at periodic time intervals and External Quantum Efficiency measurements were implemented alongside other measurements to reveal correlations between the electrical and radiative properties of the solar cells. The different imaging techniques used in this study reveal the changes in radiative emission processes and how those are correlated with performance. Alongside the indoor optoelectronic characterization of perovskite reference samples, the outdoor monitoring of two perovskite modules of the same structure for 23 weeks is reported. Significant performance degradation is presented outdoors from the first week of testing for both samples under test. The evolution of the major electrical characteristics of the mini-modules and the diurnal changes were studied in detail. Finally, dark storage recovery studies after outdoor exposure were implemented to investigate changes in the major electrical parameters. Full article

In this work, a study of a characterization technique based on open circuit voltage decay is carried out to obtain the recombination resistance of mobile charge carriers and ionic migration in triple cation perovskite solar cells. The devices were fabricated with the structure FTO/TiO₂/Cs_0.05FA_1−XMA_XPb(I_1−XBr_X)₃/spiroOMetad/Au. An equivalent circuit, created in Ngspice, was developed adjusting the capacitance and resistance values to fit the experimental open circuit voltage (V_oc) decay curves observed. The aim of this study is to associate the perovskite ionic migration with the V_oc characteristic time of charge transport in triple cation perovskite solar cells. Thus, an analysis of the open circuit voltage transient behavior was made by taking measurements of the photovoltage as a function of time. The results indicate that the technique shows charge recombination while the device is illuminated. In addition, an enhancement of the recombination resistance when increasing the FA⁺ concentration was observed. Finally, the transient behavior was associated with MA⁺, FA⁺, Cs⁺ and I⁻ migration, obtaining an ionic mobility in the range between 10⁻¹⁰ to 10⁻¹² cm² (Vs)⁻¹. Full article

The aim of this work is to investigate the degradation of perovskite solar cells (PSCs) by means of impedance spectroscopy, a highly sensitive characterization technique used to establish the electrical response of a device in a nondestructive manner. In this paper, PSCs with two different electron transport layers (ETLs) are studied: PSCs with undoped SnO₂ as an ETL are compared to PSCs with an ETL composed of graphene-doped SnO₂ (G-SnO₂). Experimental data were collected immediately after fabrication and after one week, monitoring both impedance spectroscopy and dark current-voltage (I-V) curves. It was observed that, in the case of the undoped PSCs, the degradation of the solar cells affected both the AC behavior of the devices, modifying the associated Nyquist plots, and the DC behavior, observable from the dark I-V measurements. Conversely, the solar cells with G-SnO₂ showed no variation. Considering the Nyquist plots, a quantitative analysis was performed by comparing the parameters of a proper equivalent circuit model. The results were coherent with those achieved in the DC analysis, thus proving that the analysis of impedance spectra, supported with dark I-V curves, allows one to gain a deeper knowledge of the degradation phenomena of perovskite solar cells. This study opens the door for further improvement of these devices through a better understanding of their electrical behavior. Full article

Photovoltaics are being transformed by perovskite solar cells. The power conversion efficiency of these solar cells has increased significantly, and even higher efficiencies are possible. The scientific community has gained much attention due to perovskites’ potential. Herein, the electron-only devices were prepared by spin-coating and introducing the organic molecule dibenzo-18-crown-6 (DC) to CsPbI₂Br perovskite precursor solution. The current-voltage (I-V) and J-V curves were measured. The morphologies and elemental composition information of the samples were obtained by SEM, XRD, XPS, Raman, and photoluminescence (PL) spectroscopies. The distinct impact of organic DC molecules on the phase, morphology, and optical properties of perovskite films are examined and interpreted with experimental results. The efficiency of the photovoltaic device in the control group is 9.76%, and the device efficiency gradually increases with the increase of DC concentration. When the concentration is 0.3%, the device efficiency is the best, reaching 11.57%, short-circuit current is 14.01 mA/cm², the open circuit voltage is 1.19 V, and the fill factor is 0.7. The presence of DC molecules effectively controlled the perovskite crystallization process by inhibiting the in-situ generations of impurity phases and minimizing the defect density of the film. Full article

Surface morphologies, light harvesting abilities, crystal structures, and excitonic properties of the formamiminium lead triiodide (FAPbI₃) based alloy perovskite thin films were investigated by using the scanning electron microscopic images, absorbance spectra, X-ray diffraction patterns, photoluminescence (PL) spectra and time-resolved PL decaying curves. Our experimental results show that the fresh Cs_xFA_1−xPbI₃, Rb_xFA_1−xPbI₃, and FAPb(SCN_xI_1−x)₃ alloy thin films are a pure α-phase perovskite crystal, a α-phase: δ-phase mixed perovskite crystal, and a PbI₂ crystal/α-phase: δ-phase mixed perovskite crystal at room temperatures, respectively. Among the three FAPbI₃ based alloy perovskite solar cells, the Cs_xFA_1−xPbI₃ solar cells have the better photovoltaic responses. It is noted that the high photocurrent density is mainly due to the formation of cube-like surface morphology and the long carrier lifetime of 368 ns when the Cs_xFA_1−xPbI₃ alloy perovskite thin film is used as the light-absorbing layer. Our findings provide the relation between the properties of the FAPbI₃ based alloy perovskite thin films and the photovoltaic responses of the resultant solar cells. Full article

The performance of photovoltaic solar cells is usually analyzed using continuous models, for instance, 1M5P. I-V and P-V curves are fitted by a mathematical expression from the electrical model. In the case of 1M5P, characteristics are fitted using five parameters that are obtained using a small number of I-V points from a wider set of data, keeping the curve shape given by the mathematical expression from the model. A novel model was recently proposed to overcome this issue. The d1MxP model is based on the discretization of the electrical behavior of the diodes in models such as 1M5P. The d1MxP methodology is equivalent to an analytical incremental calculation and since it connects the given points, the model error should be lower than the one obtained using models as 1M5P. It is based on the connection of adjacent points (with small voltage differences) instead of having the entire voltage range represented by some parameters (as the continuous models do, for instance, 1M5P). In this work, the d1MxP model is applied to perovskite solar cells and paint-type dye-sensitized solar cells. The aim is to analyze the behavior of the discrete model in different third-generation solar cells since their performance cannot be well characterized by the 1M5P model. The accuracy on the maximum power point is relevant, resulting in perovskite solar cells, an improvement of up to 2.61% and, in paint-type dye-sensitized solar cells, an increase of up to 5.03%. Full article

The technology of perovskite solar cells (PSC) is getting close to breaching the consumer market. Yet, one of the current challenges is to reduce the toxicity during their fabrication by reducing the use of the toxic solvents involved in the perovskite fabrication process. A good solubilization of lead halides used in hybrid perovskite preparation is required, and it is only possible with polar solvents. A mixture of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is the most popular solvent combination for a perovskite precursor solution. DMF is necessary to ensure a good dissolution of lead iodide, but it is also the most toxic solvent. In this paper, we study the replacement of the dimethylformamide with presumably less toxic alternatives, such as N-methyl-2-Pyrrolidone (NMP) and ethyl acetate (EA), for the preparation of the K_0.1FA_0.7MA_0.2PbI_2.8Cl_0.2 (KFAMA) hybrid perovskite. The perovskite thin films were investigated by various characterization techniques: X-ray diffraction, atomic force microscopy, scanning electron microscopy, and UV–vis spectroscopy, while the photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. The present study shows that by keeping the same deposition parameters as when only DMF solvent is used, the partial solvent substitution with NMP and EA gives promising results for reducing the toxicity of the fabrication process of KFAMA-based PSCs. Thus, with no specific optimization of the deposition process, and for the maximum possible partial substitution of DMF with NMP and EA solvents, the loss in the power conversion efficiency (PCE) value is only 35% and 18%, respectively, associated with the more structural defects promoted by NMP and EA. Full article

The present contribution aims to enhance solar cells’ performance via the development of advanced luminescent down-shifting based on encapsulated nanostructured perovskite materials. Here, thin films of inorganic lead halide (CsPbBr₃) perovskite nanocrystal luminophores were synthetized, by hot-injection, deposited on glass substrates by spin-coating, and encapsulated with parylene type C, via chemical vapor deposition, to protect and stabilize the films. The optical properties of these thin films were characterized by absorption, emission and 2D contour spectra, their structure by X-ray diffraction and X-ray photoelectron spectroscopy, and the morphology by Scanning Transmission Electron microscopy. I–V curve and spectral response nanocrystalline silicon photovoltaic (nc-Si:H PV) cells were studied in the absence and presence of the perovskite and parylene luminescent down-shifting layers. The incorporation of the CsPbBr₃ nanocrystals and their encapsulation with the parylene type C polymeric coating led to an increase in the current generated and the spectral response of the PV cells in the regime of the nanocrystals’ fluorescence emission. A 3.1% increase in the short circuit current density and a 5.6% increase in the power conversion efficiency were observed. Full article

The short lifetime of perovskite solar cell devices limits the application of the technique, which is yet to be resolved, despite many attempts. An important step is made here by the numerical modelling method, which reveals the decomposition kinetics under the protection of halogen bonds from excess PbI₂. Irregular diffusion behaviour of water molecules is observed when excessive PbI₂ is introduced, possibly due to the passivation and hindrance from the halogen bond, resulting in a lifetime enhancement of at least five times. The detailed kinetics are also obtained by analyzing the decomposition rate curve, offering a possible path towards high-stability PCE perovskite solar devices, by increasing the PbI₂ concentration to above the threshold, which opens an unprecedented route in perovskite solar cell research, and is, hopefully, of intrinsic interest to the broad materials research community as well. Full article

Perovskite Solar Cells are a promising solar energy harvesting technology due to their low cost and high-power conversion efficiency. A high-quality perovskite layer is fundamental for a highly efficient perovskite Solar Cell. Utilizing a gas quenching process (GQP) can eliminate the need for toxic, flammable, and expensive anti-solvents in the preparation of perovskite layers. It is a promising candidate technology for large scale preparation of perovskite layers, as it can be easily integrated in a production line by coupling up-scalable techniques. The GQP removes the need for polar solvents in the precursor solution layer by using nitrogen flow, rather than extracting them with non-polar solvents. The crystallization dynamics in this process can be significantly different. In this study, we found that the quality of perovskite crystal from GQP is much more sensitive to Lewis base molecules (LBMs) in the precursor solution than it is in anti-solvents technology. Thus, the processing parameters of the LBMs in anti-solvents technology cannot be directly transferred to the GQP. An XRD and ¹H NMR study explains the origin of the S-shaped J–V curves and how these LBMs hinder the reaction between PbI₂ and monovelent cations. Full article

The power conversion efficiency (PCE) of an Ag/spiro-OMeTAD/CH₃NH₃PbI₃ (MAPbI₃)/PCBM/mesoporous TiO₂/compact TiO₂/FTO planar solar cell with different annealing temperatures of PbI₂ and MAPbI₃ films was investigated in this study. The morphology control of a MAPbI₃ thin film plays key roles in high-efficiency perovskite solar cells. The PbI₂ films were prepared by using thermal vacuum evaporation technology, and the MAPbI₃ perovskite films were synthesized with two-step synthesis. The X-ray spectra and surface morphologies of the PbI₂ and MAPbI₃ films were examined at annealing temperatures of 80, 100, 120, and 140 °C for 10 min. The performance of the perovskite planar solar cell at an annealing temperature of 100 °C for 10 min was demonstrated. The power conversion efficiency (PCE) was about 8.66%, the open-circuit voltage (V_oc) was 0.965 V, the short-circuit current (J_sc) was 13.6 mA/cm², and the fill factor (FF) was 0.66 by scanning the density–voltage (J–V) curve. Full article

Hysteresis in perovskite solar cells is a notorious issue limiting its development in stability, reproducibility and efficiency. Ions’ migration coupled with charges’ recombination are indispensable factors to generate the hysteretic curves on the basis of experimental and theoretical calculation studies, however, the underlying physical characteristics are rarely clarified. Here, a mixed electronic-ionic drift-diffusion model combined with bulk and interfacial recombination is investigated. Positive and negative ion species could drift to and accumulate at interfaces between the perovskite/transport layers, influencing internal electric potential profiles and delaying the charges’ ejection to the transport layers. The charges might recombine spontaneously or trap-assisted, reducing the total amount of electrons and holes collected in the external circuit, leading to a diminished photocurrent. Moreover, our calculations indicate that an appropriate measurement protocol is really essential to evaluate the device performance precisely and to suppress J–V hysteresis. Meanwhile, a negligible hysteretic loop could be obtained by balancing the material properties of the transport layers and restraining the ions mobility in the perovskite layer. Full article

Development of new functional materials for novel energy conversion and storage technologies is often assisted by ab initio modeling. Specifically, for organic materials, such as electron and hole transport materials for perovskite solar cells, LED (light emitting diodes) emitters for organic LEDs (OLEDs), and active electrode materials for organic batteries, such modeling is often done at the molecular level. Modeling of aggregate-state effects is onerous, as packing may not be known or large simulation cells may be required for amorphous materials. Yet aggregate-state effects are essential to estimate charge transport rates, and they may also have substantial effects on redox potentials (voltages) and optical properties. This paper summarizes recent studies by the author’s group of aggregation effects on the electronic properties of organic materials used in optoelectronic devices and in organic batteries. We show that in some cases it is possible to understand the mechanism and predict specific performance characteristics based on simple molecular models, while in other cases the inclusion of effects of aggregation is essential. For example, it is possible to understand the mechanism and predict the overall shape of the voltage-capacity curve for insertion-type organic battery materials, but not the absolute voltage. On the other hand, oligomeric models of p-type organic electrode materials can allow for relatively reliable estimates of voltages. Inclusion of aggregate state modeling is critically important for estimating charge transport rates in materials and interfaces used in optoelectronic devices or when intermolecular charge transfer bands are important. We highlight the use of the semi-empirical DFTB (density functional tight binding) method to simplify such calculations. Full article

In this study, four organic solvents including 1,2-dichlorobenzene (DCB), chlorobenzene (CB), methylbenzene (MB), and chloroform (CF) were used as solvents in the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) electron transport layer (ETL) of perovskite solar cells (PSCs). This study observed the effects of various solvents on the surface morphology of the ETL by using an optical microscope (OM) and scanning electron microscope (SEM). The surface roughness, crystal structure, and surface element bonding of the ETL were observed using an atomic force microscope (AFM), X-ray diffractometer (XRD), and X-ray photoelectron spectroscope (XPS), respectively. The absorption spectrum of the perovskite layer was explored using an ultraviolet-visible (UV-Vis) spectrometer. The characteristics of the PSC device were analyzed in terms of its current density–voltage (J–V) curve, external quantum efficiency (EQE), and electrochemical impedance spectroscopy (EIS) measurements. The results showed that DCB is a solvent with a high boiling point, low vapor pressure, and high dielectric constant, and using DCB as the solvent for ETL, the uniformity, coverage, and surface roughness of the ETL showed better properties. The power conversion efficiency of the PSC in which DCB was used as the solvent achieved a value of 11.07%, which was higher than that of the PSCs in which other solvents were used. Full article