Performance Enhancement of Lead‐Free 2D Tin Halide Perovskite Transistors by Surface Passivation and Its Impact on Non‐Volatile Photomemory Characteristics

Abstract

Two‐dimensional (2D) tin (Sn)‐based perovskites have recently received increasing research attention for perovskite transistor application. Although some progress is made, Sn‐based perovskites have long suffered from easy oxidation from Sn2+ to Sn4+, leading to undesirable p‐doping and instability. In this study, it is demonstrated that surface passivation by phenethylammonium iodide (PEAI) and 4‐fluorophenethylammonium iodide (FPEAI) effectively passivates surface defects in 2D phenethylammonium tin iodide (PEA2SnI4) films, increases the grain size by surface recrystallization, and p‐dopes the PEA2SnI4 film to form a better energy‐level alignment with the electrodes and promote charge transport properties. As a result, the passivated devices exhibit better ambient and gate bias stability, improved photo‐response, and higher mobility, for example, 2.96 cm2 V−1 s−1 for the FPEAI‐passivated films—four times higher than the control film (0.76 cm2 V−1 s−1). In addition, these perovskite transistors display non‐volatile photomemory characteristics and are used as perovskite‐transistor‐based memories. Although the reduction of surface defects in perovskite films results in reduced charge retention time due to lower trap density, these passivated devices with better photoresponse and air stability show promise for future photomemory applications.

High-Performance Lead-Free Layered-Perovskite Photodetectors and Bipolar Transistors by Solvent Engineering

“…10−12 Furthermore, the high effective mass for the charge carriers of lead-based halide perovskite makes them difficult to transfer charge, which leads to low mobility. 13 In addition, the development of lead-based perovskite detectors is also limited by key issues such as instability and toxicity. 14 In order to solve the above problems, Pb 2+ in traditional perovskite is proposed to be replaced by Sn 2+ , considering the radius of Sn 2+ ion is similar to that of Pb 2+ (Sn: 1.18 Å, Pb: 1.19 Å).…”

“…19,20 (PEA) 2 SnI 4 has been proven to have a highly ordered crystal arrangement and provide an ideal charge-transfer behavior due to π−π stacking between benzylammonium (PEA + ) cations. 13 In 1999, Dimitrakopoulos and co-workers reported a 2D (PEA) 2 SnI 4 transistor for the first time, with a hole mobility (μ h ) of 0.62 cm 2 V −1 s −1 and a bottom-gate/top-contact structure. 21 However, after that, in 2016, Adachi and co-workers introduced a self-assembled monolayer at the interface of (PEA) 2 SnI 4 /substrate to improve the orientation of perovskite crystal, showing the top-gate/top-contact 2D perovskite transistor with a high μ h of 15 cm 2 V −1 s −1 .…”

“…The development of perovskite detectors in the early years was mainly focused on lead-based three-dimensional perovskites. However, it was found that ion migrations in the three-dimensional perovskite system could cause a serious hysteresis phenomenon, which severely impairs the device performance. − Furthermore, the high effective mass for the charge carriers of lead-based halide perovskite makes them difficult to transfer charge, which leads to low mobility . In addition, the development of lead-based perovskite detectors is also limited by key issues such as instability and toxicity .…”

“…Based on the above analysis, 2D tin-based perovskite is a promising horizontal channel material. At present, (PEA) 2 SnI 4 (PEA = C 6 H 5 C 2 H 4 NH 3 ) is the most common component for field-effect transistor (FET) applications. , (PEA) 2 SnI 4 has been proven to have a highly ordered crystal arrangement and provide an ideal charge-transfer behavior due to π–π stacking between benzylammonium (PEA + ) cations . In 1999, Dimitrakopoulos and co-workers reported a 2D (PEA) 2 SnI 4 transistor for the first time, with a hole mobility (μ h ) of 0.62 cm 2 V –1 s –1 and a bottom-gate/top-contact structure .…”

Precursor Solution Aging: A Universal Strategy Modulating Crystallization of Two-Dimensional Tin Halide Perovskite Films

“…Afterward, the solution aging effect on the perovskite film crystallization was examined with a primary focus on (PEA) 2 SnI 4 , since it is the most widely explored 2D Sn-perovskite candidate with great potential in diverse optoelectronic devices. − The X-ray diffraction (XRD) patterns of (PEA) 2 SnI 4 thin films deposited from fresh and 3-day aged solutions exhibit stable layered structures with (002), (004), (006), (008), (0010), and (0012) peaks at 5.5, 10.9, 16.4, 21.9, 27.4, 33.0, and 38.7°, respectively (Figure a). A residual SnI 2 characteristic peak at around 25.6° was identified in the film from the fresh precursor solution, but it disappeared after 3 days of aging, indicating an incomplete reaction of precursor compounds in the fresh solution.…”