Liquid Phase Exfoliated Indium Selenide Based Highly Sensitive Photodetectors

Abstract

Layered semiconductors of the IIIA-VIA group have attracted considerable attention in (opto)electronic applications thanks to their atomically thin structures and their thickness-dependent optical and electronic properties, which promise ultrafast response and high sensitivity. In particular, 2D indium selenide (InSe) has emerged as a promising candidate for the realization of thin-film field effect transistors and phototransistors due to its high intrinsic mobility (>10 2 cm 2 V −1 s −1 ) and the direct optical transitions in an energy range suitable for visible and near-infrared light detection. A key requirement for the exploitation of large-scale (opto)electronic applications relies on the development of low-cost and industrially relevant 2D material production processes, such as liquid phase exfoliation, combined with the availability of high-throughput device fabrication methods. Here, a β polymorph of indium selenide (β-InSe) is exfoliated in isopropanol and spray-coated InSe-based photodetectors are demonstrated, exhibiting high responsivity to visible light (maximum value of 274 A W −1 under blue excitation 455 nm) and fast response time (15 ms). The devices show a gate-dependent conduction with an n-channel transistor behavior.Overall, this study establishes that liquid phase exfoliated β-InSe is a valid candidate for printed high-performance photodetectors, which is critical for the development of industrial-scale 2D material-based optoelectronic devices.

Liquid‐Phase Exfoliated Gallium Selenide for Light‐Driven Thin‐Film Transistors

“…[ 21 ] We found a field‐effect differential mobility of the film (μ fe —defined in the linear region, V D < V G – V th , of the I D – V G curve in Figure 3d) of ≈10 –3 cm 2 V −1 s −1 for a V G in the range between −40 and 0 V. We attribute the decrease in mobility compared to single flake values to the presence of traps and surface oxidation caused by the spray deposition processing in air, which increases the contact resistance between the interconnected flakes. [ 85,146 ]…”

“…The presence of carrier generation, trapping, and recombination processes within the ε‐GaSe can be studied by the power dependence of the photodetector. [ 85,147 ] In fact, an ideal thin‐film photodetector has a wide linear dynamic range, [ 154–157 ] in which the photocurrent I ph is proportional to the incident light power ( I ≈ P ϑ —with the power exponent ϑ = 1). [ 85,147 ] However, in the ε‐GaSe phototransistor, a nonunity exponent of 0 < ϑ < 1 was found that we assign to charge carrier trapping.…”

“…[ 85,147 ] In fact, an ideal thin‐film photodetector has a wide linear dynamic range, [ 154–157 ] in which the photocurrent I ph is proportional to the incident light power ( I ≈ P ϑ —with the power exponent ϑ = 1). [ 85,147 ] However, in the ε‐GaSe phototransistor, a nonunity exponent of 0 < ϑ < 1 was found that we assign to charge carrier trapping. [ 85,147 ] Figure 4b reports the photocurrent I ph as a function of the incident light power, using a LED with an emission peak at 530 nm (FWHM = 42 nm).…”

“…[ 79 ] Moreover, due to low vapor pressure ( P v ≈ 0.05 kPa) [ 80 ] and high boiling point ( T b ≈ 200 °C), [ 81 ] the aforementioned solvents leave contaminants [ 82–84 ] in the deposited layers of the exfoliated materials, affecting the electronic properties of the devices. [ 72,85 ] Hence, LPE of 2D materials in low boiling point solvents, such as acetone, [ 86 ] alcohols, [ 57,72,85,87–94 ] and water/alcohol mixtures [ 57,72,82,88,95 ] has been investigated as a strategy to reduce the use of toxic chemicals, minimizing the contamination by solvent residuals in films composed of such flakes. The dispersions produced by LPE contain exfoliated flakes that differ in lateral size and thickness.…”

“…To date, several techniques have been investigated, such as inkjet [ 72,73 ] and screen [ 69 ] printing. Spray coating is a forefront technique in electronics, [ 100–102 ] being an industrially compatible process that is already applied, for example, to the implementation of perovskite‐based solar cells, [ 103,104 ] InSe‐based photodetectors, [ 85 ] carbon nanotube‐based gas and temperature sensors [ 105,106 ] and can be further optimized to produce highly uniform ε‐GaSe films. ε‐Gallium selenide has been recently exfoliated through LPE by using isopropyl alcohol (IPA), [ 87 ] allowing the effective deposition of a percolative network of flakes and the implementation of a photoelectrochemical (PEC) photodetector.…”