Effectively Enhanced Broadband Phototransistors Based on Multilayer WSe₂/Pentacene

Abstract

wavelength of 775 nm. Their synthesis and fabrication are considerably challenging, not suitable for further commercial process technology. On the other hand, multilayer WSe 2 could afford wider spectral bands covering NIR owing to the narrow energy bandgap. It could indicate multilayer WSe 2 is a capable active matrix for broadband applications.Meanwhile, some strategies to improve the photoresponsivity of multilayer WSe 2 have been still demonstrated by forming p-n junctions with different 2D TMDs [4,5] or localized quantum dots, [6,7] the transformation of device structures. [8,9] These methods could enhance the photoresponsivity in phototransistors, but there are still rooms to be improved precisely and practically. One of the promising approaches is forming the hybrid structure of multilayer WSe 2 with organic materials. Organic materials are feasible to construct scalable film or discontinuous islands as patches or rods at low temperature and provide massive absorption under broadband lights, resulting in the accumulated excessive excitons in the entire active matrix of phototransistors. Besides, excitons from singlet or triplet states could diffuse into organic semiconductors, and the possible exciton diffusion lengths vary from a few nm to µm depending on the materials. [10,11] Pentacene (C 22 H 14 ) is a p-type organic semiconductor consisting of five benzene rings linearly connected. Pentacene exhibits significant absorption under broad spectral lights and offers considerably long exciton diffusion lengths around 0.55 µm. [11] It can be directly grown on WSe 2 at low temperatures by a concise evaporation process without any undesirable electronic deformations. The WSe 2 and pentacene's hybrid structure could potentially enhance optoelectronic properties in multilayer WSe 2 .Herein, we've designed and demonstrated the multilayer WSe 2 /pentacene-based broadband phototransistors. Pentacene islands are formed on the multilayer WSe 2 to enhance the active matrix's photoresponsivity under broadband lights. Pentacene could offer a wide absorption band and generate enormous excitons. Its exciton diffusion length is sufficient to transfer excitons from pentacene to WSe 2 at the interface. Moreover, WSe 2 -and WSe 2 /pentacene-based phototransistors are examined under visible red and NIR light irradiations with different laser powers. The photocurrent (I ph ) and the photoresponsivity (R ph ) in WSe 2 /pentacene transistors are 1.41 µA and 19.313 A W −1 for 638-nm light and 0.20 µA and 1.

Low‐Energy‐Consumption and Electret‐Free Photosynaptic Transistor Utilizing Poly(3‐hexylthiophene)‐Based Conjugated Block Copolymers

“…Photoinduced excitons have been known to play a nontrivial role in photonic transistor devices. [ 29 , 30 ] Next, the highest occupied molecular orbital (HOMO) levels for the P3HT‐based BCPs and insulating homopolymers were measured using cyclic voltammetry (CV), as shown in Figure S5 (Supporting Information), and the resultant HOMO and the lowest unoccupied molecular orbital (LUMO) levels are summarized in Figure S6 and Table S1 (Supporting Information). The energy levels (HOMO, LUMO) of the insulating homopolymers were (−1.82, −5.61), (−1.69, −6.15), (−1.66, −6.22), and (−1.73, −6.53) eV for PVN, P2VP, PS, and PBA, respectively.…”

Homogeneous in-plane WSe2 P–N junctions for advanced optoelectronic devices

“…Through the above equations, the R and EQE of our p–n junction are calculated to be ∼7.1 × 10 4 mA W −1 and ∼228%, respectively, outperforming other reported results as summarized in Table 2. 10,12,14–17,19,56–59 The high values of R and EQE also demonstrate that the plasma-treated WSe 2 p–n junction exhibits a good photoresponsivity. In addition, D * is another figure of merit for photodetector devices to evaluate the detector sensitivity, which is generally calculated using the following equation of D * (Jones) = ( R · A 1/2 )/( I dark ·2e) 1/2 .…”

N‐Type Doping and Passivation of Black Phosphorus Using Pentacene for Infrared Polarization‐Sensitive Photodetection and Imaging

“…This indicates that exciton migration occurs at the interface between pentacene and FL-BP flake, leading to the quenching of PL. [50] In order to study the doping effect of pentacene on FL-BP flakes, we prepared a typical three-terminal field effect transistor (FET) device. The output characteristic curve of FL-BP device before and after passivation under 0 V gate bias is shown in Figure 3b.…”