ABSTRACT
Resistive switching random-access memory (ReRAM) devices based on organic-inorganic halide perovskites (OIHPs) have emerged as a new class of data storage devices. Recently, two-dimensional (2D) OIHPs have attracted much attention for ReRAM applications because of their structural diversity and superior stability. Here, the RS characteristics of ReRAM devices fabricated utilizing pure 2D Ruddlesden-Popper (RP) perovskite crystals, namely (TEA)2PbBr4 and (TEA)2PbI4, are reported. The RS memory devices exhibit reliable and reproducible bipolar switching properties with high ON/OFF ratio (â¼104), excellent data retention of over 104 s, and good endurance characteristics of 200 cycles. This study investigates temperature-dependent RS behaviors, elucidating the creation and annihilation of a conducting pathway in the presence of an external electric field. Additionally, the RS property of 2D RP perovskite-based memory devices is found to be retained over 45 days at ambient conditions under a relative humidity of 47% ± 4%. Our findings may accelerate the technological deployment of stable 2D perovskite-based RS memory devices for successful logic application.
ABSTRACT
Two-dimensional (2D) transition metal dichalcogenides (TMDs) and perovskites hold substantial promise for various optoelectronic applications such as light emission, photodetection, and energy harvesting. However, each of these materials possesses certain limitations that can be overcome by synergistically combining them to form heterostructures, thereby unveiling intriguing optical properties. In this study, we present an uncomplicated technique for crafting a van der Waals (vdW) heterojunction comprising monolayer WS2 and a Ruddlesden-Popper (RP) perovskite, namely (TEA)2PbI4. By utilizing ultrafast transient absorption (TA) spectroscopy, we explored the charge carrier dynamics within the WS2/(TEA)2PbI4 heterostructure. Our findings uncover a type-II band alignment in the heterostructure, facilitating rapid (within 260 fs) hole transfer from WS2 to the perovskite and leading to the formation of interlayer excitons (IXs) with a much longer lifetime (728 ps). This strategic approach has the potential to contribute to the development of hybrid systems aimed at achieving high-performance optoelectronic devices.
ABSTRACT
We investigate the hot carrier and exciton dynamics in two-dimensional (2D) metal halide perovskites using time-resolved spectroscopy. 2D perovskite films were prepared with and without dimethyl sulfoxide treatment to elucidate the effect of film processing techniques on optoelectronic properties. Femtosecond transient absorption measurements reveal that the charge carrier dynamics are different in the two samples, and excitons survive for a longer time in the treated sample than the untreated one. While the early-time carrier dynamics in the untreated sample are dominated by charges trapped by defect states, the hot free carriers govern the dynamics in the treated sample due to fewer defects in it. Morphological and other spectroscopic studies, including time-resolved photoluminescence, further suggest the formation of more defects in the untreated sample. These results can guide the future development of efficient 2D perovskite-based optoelectronic devices.
ABSTRACT
Perovskite solar cells (PSCs) with superior performance have been recognized as a potential candidate in photovoltaic technologies. However, defects in the active perovskite layer induce nonradiative recombination which restricts the performance and stability of PSCs. The construction of a thiophene-based 2D structure is one of the significant approaches for surface passivation of hybrid PSCs that may combine the benefits of the stability of 2D perovskite with the high performance of three-dimensional (3D) perovskite. Here, a sulfur-rich spacer cation 2-thiopheneethylamine iodide (TEAI) is synthesized as a passivation agent for the construction of a three-dimensional/two-dimensional (3D/2D) perovskite bilayer structure. TEAI-treated PSCs possess a much higher efficiency (20.06%) compared to the 3D perovskite (MA0.9FA0.1PbI3) devices (17.42%). Time-resolved photoluminescence and femtosecond transient absorption spectroscopy are employed to investigate the effect of surface passivation on the charge carrier dynamics of the 3D perovskite. Additionally, the stability test of TEAI-treated perovskite devices reveals significant improvement in humid (RH â¼ 46%) and thermal stability as the sulfur-based 2D (TEA)2PbI4 material self-assembles on the 3D surface, making the perovskite surface hydrophobic. Our findings provide a reliable approach to improve device stability and performance successively, paving the way for industrialization of PSCs.