Improving Photovoltaic Performance of Hybrid Organic-Inorganic MAGeI3 Perovskite Solar Cells via Numerical Optimization of Carrier Transport Materials (HTLs/ETLs)

Advanced Optoelectronic Modeling and Optimization of HTL-Free FASnI3/C60 Perovskite Solar Cell Architecture for Superior Performance

In this study, a novel perovskite solar cell (PSC) architecture is presented that utilizes an HTL-free configuration with formamide tin iodide (FASnI3) as the active layer and fullerene (C60) as the electron transport layer (ETL), which represents a pioneering approach within the field. The elimination of hole transport layers (HTLs) reduces complexity and cost in PSC heterojunction structures, resulting in a simplified and more cost-effective PSC structure. In this context, an HTL-free tin HC(NH2)2SnI3-based PSC was simulated using the solar cell capacitance simulator (SCAPS) within a one-dimensional framework. Through this approach, the device performance of this novel HTL-free FASnI3-based PSC structure was engineered and evaluated. Key performance parameters, including the open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), power conversion efficiency (PCE), I-V characteristics, and quantum efficiency (QE), were systematically assessed through the modulation of physical parameters across various layers of the device. A preliminary analysis indicated that the HTL-free configuration exhibited improved I-V characteristics, with a PCE increase of 1.93% over the HTL configuration due to improved electron and hole extraction characteristics, reduced current leakage at the back contact, and reduced trap-induced interfacial recombination. An additional boost to the device's key performance parameters has been achieved through the further optimization of several physical parameters, such as active layer thickness, bulk and interface defects, ETL thickness, carrier concentration, and back-contact materials. For instance, increasing the thickness of the active layer PSC up to 1500 nm revealed enhanced PV performance parameters; however, further increases in thickness have resulted in performance saturation due to an increased rate of hole-electron recombination. Moreover, a comprehensive correlation study has been conducted to determine the optimum thickness and donor doping level for the C60-ETL layer in the range of 10-200 nm and 1012-1019 cm-3, respectively. Optimum device performance was observed at an ETL-C60 ultra-thin thickness of 10 nm and a carrier concentration of 1019 cm-3. To maintain improved PCEs, bulk and interface defects must be less than 1016 cm-3 and 1015 cm-3, respectively. Additional device performance improvement was achieved with a back-contact work function of 5 eV. The optimized HTL-free FASnI3 structure demonstrated exceptional photovoltaic performance with a PCE of 19.63%, Voc of 0.87 V, Jsc of 27.86 mA/cm2, and FF of 81%. These findings highlight the potential for highly efficient photovoltaic (PV) technology solutions based on lead-free perovskite solar cell (PSC) structures that contribute to environmental remediation and cost-effectiveness.

Long-Term Comparisons of Photoluminescence Affected by Organic Cations of Formamidinium and Methylammonium in Monophasic Lead Iodide Perovskite Quantum Dots

This study compared the photoluminescence (PL) stabilities of formamidinium (FA) and methylammonium (MA) in lead iodide perovskite quantum dots (QDs). To exclude other factors, such as size and purity, that may affect stability, MAPbI3 and FAPbI3 QDs with nearly identical sizes (~10.0 nm) were synthesized by controlling the ligand concentration and synthesis temperature. Transmission electron microscopy images and X-ray diffraction patterns confirmed homogeneous single-phase perovskite structures. Additionally, the bandgaps and sizes of the synthesized QDs closely matched those of the infinite quantum well model, which guaranteed that the photostability was solely caused by the different organic molecules in the two QDs. We analyzed the PL peak centers and full-width at half maximum of the QDs for 32 days. The enhanced stability of FAPbI3 was found to be caused by the nearly zero redshift (1.615 eV) of its PL peak, in contrast to the redshift (1.685→1.670 eV) of MAPbI3.

Self-Assembled Monolayer-Based Hole-Transporting Materials for Perovskite Solar Cells

Ever since self-assembled monolayers (SAMs) were adopted as hole-transporting layers (HTL) for perovskite solar cells (PSCs), numerous SAMs for HTL have been synthesized and reported. SAMs offer several unique advantages including relatively simple synthesis, straightforward molecular engineering, effective surface modification using small amounts of molecules, and suitability for large-area device fabrication. In this review, we discuss recent developments of SAM-based hole-transporting materials (HTMs) for PSCs. Notably, in this article, SAM-based HTMs have been categorized by similarity of synthesis to provide general information for building a SAM structure. SAMs are composed of head, linker, and anchoring groups, and the selection of anchoring groups is key to design the synthetic procedure of SAM-based HTMs. In addition, the working mechanism of SAM-based HTMs has been visualized and explained to provide inspiration for finding new head and anchoring groups that have not yet been explored. Furthermore, both photovoltaic properties and device stabilities have been discussed and summarized, expanding reader's understanding of the relationship between the structure and performance of SAMs-based PSCs.