An intrinsic electrical conductivity study of perovskite powders MAPbX3 (X = I, Br, Cl) to investigate its effect on their photovoltaic performance.

An investigation into the intrinsic electrical conductivity of perovskite powders MAPbX3, where X represents iodine (I), bromine (Br), or chlorine (Cl), was conducted to explore its impact on their photovoltaic performance. Results revealed that MAPbCl3 demonstrated light absorption ability in the ultraviolet and visible regions, while MAPbBr3 showed capacity for light absorption at longer wavelengths in the visible spectrum. On the other hand, MAPbI3 exhibited good absorption at longer wavelengths, indicating its ability to absorb light in the near-infrared region. The optical bandgap of each perovskite was determined to be 2.90 eV for MAPbCl3, 2.20 eV for MAPbBr3, and 1.47 eV for MAPbI3. The electrical conductivities of these powders were measured in-plane using the four-probe method and through-plane by electrochemical impedance spectroscopy (EIS). Electrochemical impedance spectroscopy (EIS) studies revealed a significant change in the conductivity of the MAPbI3 perovskite at temperatures between 80 °C and 100 °C. This change could be attributed to structural modifications induced when the temperature exceeds these values. The through-plane conductivity changed from 3 × 10-8 S cm-1 at 60 °C to approximately 6 × 10-5 S cm-1 at 120 °C and around 2 × 10-3 S cm-1 at 200 °C. Meanwhile, the sheet conductivity (in-plane conductivity) measurements performed at ambient temperature reveal that sheet conductivities are 489 × 103 S m-1, 486 × 103 S m-1 and 510 × 103 S m-1 for MAPbBr3, MAPbCl3 and MAPbI3, respectively. This study provides valuable insights for optimizing the performance of perovskite solar cells. Understanding how dopants influence the electrical conductivity and photovoltaic properties of the perovskite material, this work will enable researchers to design and engineer more efficient and stable solar cell devices based on MAPbX3 perovskites.

Manufacture of High-Efficiency and Stable Lead-Free Solar Cells through Antisolvent Quenching Engineering.

Antisolvent quenching has shown to significantly enhance several perovskite films used in solar cells; however, no studies have been conducted on its impact on MASnI3. Here, we investigated the role that different antisolvents, i.e., diethyl ether, toluene, and chlorobenzene, have on the growth of MASnI3 films. The crystallinity, morphology, topography, and optical properties of the obtained thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) measurements, and UV-visible spectroscopy. The impact of the different antisolvent treatments was evaluated based on the surface homogeneity as well as the structure of the MASnI3 thin films. In addition, thermal annealing was optimized to control the crystallization process. The applied antisolvent was modified to better manage the supersaturation process. The obtained results support the use of chlorobenzene and toluene to reduce pinholes and increase the grain size. Toluene was found to further improve the morphology and stability of thin films, as it showed less degradation after four weeks under dark with 60% humidity. Furthermore, we performed a simulation using SCAPS-1D software to observe the effect of these antisolvents on the performance of MASnI3-based solar cells. We also produced the device FTO/TiO2/MASnI3/Spiro-OMeTAD/Au, obtaining a remarkable photoconversion efficiency (PCE) improvement of 5.11% when using the MASnI3 device treated with chlorobenzene. A PCE improvement of 9.44% was obtained for the MASnI3 device treated with toluene, which also showed better stability. Our results support antisolvent quenching as a reproducible method to improve perovskite devices under ambient conditions.

Investigation of the Surface Coating, Humidity Degradation, and Recovery of Perovskite Film Phase for Solar-Cell Applications.

Presently, we inquire about the organic/inorganic cation effect on different properties based on structure, morphology, and steadiness in preparing a one-step solution of APbI3 thin films, where A = MA, FA, Cs, using spin coating. This study was conducted to understand those properties well by incorporating device modeling using SCAPS-1D software and to upgrade their chemical composition. X-ray diffraction (XRD) was used to analyze the crystal structures. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were conducted to characterize the surface morphology; photoluminescence, Transmission Electron Microscopy (TEM), and a UV-Visible spectrometer helped us to study the optical properties. The (110) plane is where we found the perovskite's crystalline structure. According to the XRD results and by changing the type of cation, we influence stabilization and the growth of the APbI3 absorber layer. Hither, a homogenous, smooth-surfaced, pinhole-free perovskite film and large grain size are results from the cesium cation. For the different cations, the band gap's range, revealed by the optical analysis, is from 1.4 to 1.8 eV. Moreover, the stability of CsPbI3 remains excellent for two weeks and in a ~60% humid environment. Based on the UV-Visible spectrometer and photoluminescence characterization, a numerical analysis for fabricated samples was also performed for stability analysis by modeling standard solar-cell structures HTL/APbI3/ETL. Modeling findings are in good agreement with experimental results that CsPbI3 is more stable, showing a loss % in PCE of 14.28%, which is smaller in comparison to FAPbI3 (44.46%) and MAPbI3 (20.24%).

Study of the Degree of Cure through Thermal Analysis and Raman Spectroscopy in Composite-Forming Processes.

The curing of composite materials is one of the parameters that most affects their mechanical behavior. The inspection methods used do not always allow a correct characterization of the curing state of the thermosetting resins. In this work, Raman spectroscopy technology is used for measuring the degree of cure. The results are compared with conventional thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscope (SEM). Carbon fiber specimens manufactured with technologies out of autoclave (OoA) have been used, with an epoxy system Prepreg System, SE 84LV. The results obtained with Raman technology show that it is possible to verify the degree of polymerization, and the information is complementary from classical thermal characterization techniques such as TGA and DSC; thus, it is possible to have greater control in curing and improving the quality of the manufactured parts.