In Silico Investigation of the Impact of Hole-Transport Layers on the Performance of CH3NH3SnI3 Perovskite Photovoltaic Cells

Device modeling and numerical study of a double absorber solar cell using a variety of electron transport materials

In photovoltaic (PV) technology, halide perovskites are the prospective choice for highly efficient solar absorbers because of their superior optical properties, enhanced efficiency, lightweight, and low cost. In this study, a double absorber solar device using an inorganic perovskite called NaZn₀.₇Cu₀.₃Br₃ as the top absorber layer and MASnI₃ as the bottom absorber layer is analyzed utilizing the SCAPS-1D simulation tool. The primary goal of this study is to look for a device architecture with a higher efficiency level. Here, current matching over two active layers is performed by adjusting the thickness of both active layers. This research focuses on the effect of various electron transport layers, varied absorber layer thicknesses, temperatures, absorber defect density, and metalwork functions on the performance of the proposed photo-voltaic cells. After researching a variety of solar cell architectures, it is revealed that FTO/ZnO/ NaZn₀.₇Cu₀.₃Br₃ / MASnI₃ / CuO /Au arrangement has an open circuit voltage of 1.1373 V, Fill Factor of 82.13%, short circuit current density of 34.71 mA/cm² and highest power conversion efficiency (PCE) of 32.42%. Here, the simulations of the device indicated that a thickness of around 1 μm for the MASnI₃ absorber was optimum. Additionally, the results of the simulations demonstrate that the efficiency of the device rapidly drops with increasing absorbers defect density and temperature, and device structures are steady at 300 K. Finally; any conductor can make the anode if its work function is larger than or equal to 5.10 eV.

Direct Nanoscale Visualization of the Electric-Field-Induced Aging Dynamics of MAPbI3 Thin Films

Perovskite solar cells represent the most attractive emerging photovoltaic technology, but their practical implementation is limited by solar cell devices' low levels of operational stability. The electric field represents one of the key stress factors leading to the fast degradation of perovskite solar cells. To mitigate this issue, one must gain a deep mechanistic understanding of the perovskite aging pathways associated with the action of the electric field. Since degradation processes are spatially heterogeneous, the behaviors of perovskite films under an applied electric field should be visualized with nanoscale resolution. Herein, we report a direct nanoscale visualization of methylammonium (MA⁺) cation dynamics in methylammonium lead iodide (MAPbI₃) films during field-induced degradation, using infrared scattering-type scanning near-field microscopy (IR s-SNOM). The obtained data reveal that the major aging pathways are related to the anodic oxidation of I^- and the cathodic reduction of MA⁺, which finally result in the depletion of organic species in the channel of the device and the formation of Pb. This conclusion was supported by a set of complementary techniques such as time-of-flight secondary ion mass spectrometry (ToF-SIMS), photoluminescence (PL) microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) microanalysis. The obtained results demonstrate that IR s-SNOM represents a powerful technique for studying the spatially resolved field-induced degradation dynamics of hybrid perovskite absorbers and the identification of more promising materials resistant to the electric field.

Towards High-Efficiency Photon Trapping in Thin-Film Perovskite Solar Cells Using Etched Fractal Metadevices

Reflective loss is one of the main factors contributing to power conversion efficiency limitation in thin-film perovskite solar cells. This issue has been tackled through several approaches, such as anti-reflective coatings, surface texturing, or superficial light-trapping metastructures. We report detailed simulation-based investigations on the photon trapping capabilities of a standard Methylammonium Lead Iodide (MAPbI3) solar cell, with its top layer conveniently designed as a fractal metadevice, to reach a reflection value R<0.1 in the visible domain. Our results show that, under certain architecture configurations, reflection values below 0.1 are obtained throughout the visible domain. This represents a net improvement when compared to the 0.25 reflection yielded by a reference MAPbI3 having a plane surface, under identical simulation conditions. We also present the minimum architectural requirements of the metadevice by comparing it to simpler structures of the same family and performing a comparative study. Furthermore, the designed metadevice presents low power dissipation and exhibits approximately similar behavior regardless of the incident polarization angle. As a result, the proposed system is a viable candidate for being a standard requirement in obtaining high-efficiency perovskite solar cells.

Studies of Performance of Cs2TiI6-XBrX (Where x = 0 to 6)-Based Mixed Halide Perovskite Solar Cell with CdS Electron Transport Layer

The present research work represents the numerical study of the device performance of a lead-free Cs₂TiI_6-XBr_X-based mixed halide perovskite solar cell (PSC), where x = 1 to 5. The open circuit voltage (V_OC) and short circuit current (J_SC) in a generic TCO/electron transport layer (ETL)/absorbing layer/hole transfer layer (HTL) structure are the key parameters for analyzing the device performance. The entire simulation was conducted by a SCAPS-1D (solar cell capacitance simulator- one dimensional) simulator. An alternative FTO/CdS/Cs₂TiI_6-XBr_X/CuSCN/Ag solar cell architecture has been used and resulted in an optimized absorbing layer thickness at 0.5 µm thickness for the Cs₂TiBr₆, Cs₂TiI₁Br₅, Cs₂TiI₂Br₄, Cs₂TiI₃Br₃ and Cs₂TiI₄Br₂ absorbing materials and at 1.0 µm and 0.4 µm thickness for the Cs₂TiI₅Br₁ and Cs₂TiI₆ absorbing materials. The device temperature was optimized at 40 °C for the Cs₂TiBr₆, Cs₂TiI₁Br₅ and Cs₂TiI₂Br₄ absorbing layers and at 20 °C for the Cs₂TiI₃Br₃, Cs₂TiI₄Br₂, Cs₂TiI₅Br₁ and Cs₂TiI₆ absorbing layers. The defect density was optimized at 10¹⁰ (cm^-3) for all the active layers.

IR Spectroscopic Degradation Study of Thin Organometal Halide Perovskite Films

The advantages of IR spectroscopy include relatively fast analysis and sensitivity, which facilitate its wide application in the pharmaceutical, chemical and polymer sectors. Thus, IR spectroscopy provides an excellent opportunity to monitor the degradation and concomitant evolution of the molecular structure within a perovskite layer. As is well-known, one of the main limitations preventing the industrialization of perovskite solar cells is the relatively low resistance to various degradation factors. The aim of this work was to study the degradation of the surface of a perovskite thin film CH₃NH₃PbI_3-xCl_x caused by atmosphere and light. To study the surface of CH₃NH₃PbI_3-xCl_x, a scanning electron microscope, infrared (IR) spectroscopy and optical absorption were used. It is shown that the degradation of the functional layer of perovskite proceeds differently depending on the acting factor present in the surrounding atmosphere, whilst the chemical bonds are maintained within the perovskite crystal structure under nitrogen. However, when exposed to an ambient atmosphere, an expansion of the NH₃⁺ band is observed, which is accompanied by a shift in the N-H stretching mode toward higher frequencies; this can be explained by the degradation of the perovskite surface due to hydration. This paper shows that the dissociation of H₂O molecules under the influence of sunlight can adversely affect the efficiency and stability of the absorbing layer. This work presents an approach to the study of perovskite structural stability with the aim of developing alternative concepts to the fabrication of stable and sustainable perovskite solar cells.