Photodetectors Based on Two‐Dimensional Layered Materials Beyond Graphene

Abstract

1 of 41) 1603886However, despite its high absorption coefficient, [15] single-layer graphene can absorb only ≈2.3% of incident visible and infrared (IR) light due to its thinness, [16,17] which is undesirable for high performance photodetectors that require strong light absorption. Graphene's gaplessness also leads to short photocarrier lifetime in pure graphene, which is unfavorable for efficient photocurrent generation. [18][19][20] In addition to graphene, this family of materials contains an extremely large range of other 2D-layered materials that have recently attracted much research interest. [1][2][3][4][5][6][7][8] Similar to graphene, being atomically thin, these materials exhibit a wide range of unique electrical, optical, thermal, and mechanical properties that can never be seen in their three-dimensional (3D) bulk counterparts due to the dimensionality confinement effect and modulation in their band structures. [21,22] These 2D-layered materials can be metals, semiconductors, insulators, superconductors, topological insulators, or paramagnetic, diamagnetic, ferromagnetic, or anti-ferromagnetic, etc., depending on their composition and phases. [23,24] Among these materials, particular attention has been paid to 2D layered semiconductors thanks to their unique electronic [2,[24][25][26] and optoelectronic properties, [27,28] which arise from their appreciable bandgaps ranging from IR to UV and throughout the visible range.The optical and optoelectronic properties of 2D layered semiconductors are strongly dependent on their number of layers due to the quantum confinement effects in the out-of-plane direction and changes in symmetry. [29,30] This layer-dependent modulation of physical properties, such as bandgap structure, is particularly evident in the semiconducting transition metal dichalcogenides (TMDs) [2,7,29,31,32] and few-layer black phosphorus (BP). [33,34] Another effect induced by vertical quantum confinement is the increased absorption efficiency, which results from the strongly bound excitons due to the reduced thickness. [29,35,36] The atomic thickness of a 2D layered semiconductor also leads to high transparency [37] and good mechanical flexibility, [38] properties of particular interest for novel device applications such as flexible, wearable, or portable electronics. Despite their high transparency, 2D layered semiconductors can strongly interact with incident light, leading to enhanced photon absorption and electron-hole creation due to the existence of Van Hove singularities in their electronic density of states. [39] It has also been reported that 2D layered materials possess extraordinary elastic modulus and large strain (>10%) before rupture, [40][41][42][43] which allow for tuning their electronic and optical properties Following a significant number of graphene studies, other two-dimensional (2D) layered materials have attracted more and more interest for their unique structures and distinct physical properties, which has opened a window for realizing novel electronic or optoelectr...

Lattice Vibration of Layered GaTe Single Crystals

“…The few-layered two-dimensional GaTe materials with direct band gap were successfully prepared and applied as the channel of photodetectors [12][13][14][15], which exhibited a fairly high photoresponsivity of 10 4 A/W and a very fast photoresponse time less than 20 ms [13], which was much better than other layered materials [16,17]. Such wonderful performance may relate to its unique monoclinic structure, however, the crystal structure of GaTe is still not fully understood.…”

Graphene, Transition Metal Dichalcogenides, and Perovskite Photodetectors

“…Their exceptional properties including an adjustable spectral absorption range, high carrier mobility, long diffusion lengths, and the affordability of fabrication render them one of the most exceptional optoelectronic materials for photoelectrical device applications especially in photodetectors [41]. Organic-inorganic hybrid halide perovskites have the same chemical formula ABX 3 . The A cation can be organic species including CH 3 CH 2 NH 3 + (EA), HC(NH 2 ) 2 + (FA), and CH 3 NH 3 (MA) or inorganic species such as Cs, Rb, K, and Na, and their ionic radiuses decrease gradually.…”

“…, strong photoluminescence, good chemical stability and mechanical flexibility, and so on [3]. (Figure 6b), but the response time can be several seconds, which is influenced by the surroundings of MoS 2 [32].…”

“…Photodetectors that operate via the photovoltaic effect are usually called photodiodes. A photodiode photodetector can function at two modes under illumination: the photovoltaic mode at zero bias and the photoconductive mode under reverse bias [3,16]. The charge-separation mechanism is shown in Figure 3.…”

“…The in-plane atoms are held together by tight covalent or ionic bonds along 2D directions to form atomic layers, while the atomic layers are bonded together by weak van der Waals interactions along the out-of-plane direction [1][2][3]. Nicolosi et al summarized different types of layered materials, which can be grouped into diverse families.…”