Highly Efficient Van Der Waals Heterojunction on Graphdiyne toward the High‐Performance Photodetector

Abstract Graphdiyne (GDY), a new 2D material, has recently proven excellent performance in photodetector applications due to its direct bandgap and high mobility. Different from the zero‐gap of graphene, these preeminent properties made GDY emerge as a rising star for solving the bottleneck of graphene‐based inefficient heterojunction. Herein, a highly effective graphdiyne/molybdenum (GDY/MoS2) type‐II heterojunction in a charge separation is reported toward a high‐performance photodetector. Characterized by robust electron repulsion of alkyne‐rich skeleton, the GDY based junction facilitates the effective electron–hole pairs separation and transfer. This results in significant suppression of Auger recombination up to six times at the GDY/MoS2 interface compared with the pristine materials owing to an ultrafast hot hole transfer from MoS2 to GDY. GDY/MoS2 device demonstrates notable photovoltaic behavior with a short‐circuit current of −1.3 × 10−5 A and a large open‐circuit voltage of 0.23 V under visible irradiation. As a positive‐charge‐attracting magnet, under illumination, alkyne‐rich framework induces positive photogating effect on the neighboring MoS2, further enhancing photocurrent. Consequently, the device exhibits broadband detection (453–1064 nm) with a maximum responsivity of 78.5 A W−1 and a high speed of 50 µs. Results open up a new promising strategy using GDY toward effective junction for future optoelectronic applications.


Synthesis of 1,3,5-Triethynylbenzne (TEB)
This product is then dissolved in CH 2 Cl 2 (2.46 mL), followed by adding a mixture of methanol/ sodium hydroxide (2.46 mL, 0.186mg).Then, the mixture is stirred under Ar gas at room temperature for 12h.Once the reaction is complete, the solvent evaporates.Finally, the crude is worked-up by CH 2 Cl 2 , water, and brine, followed by dry over anhydrous Na 2 SO 4 to give the 1,3,5-triethynylbenzenze as the white color (111 mg, 96%).To easier explain the carrier movement behavior at the junction, ultraviolet spectra (UPS) are used to calculate the relative position of Fermi energy (E f ) and valence band maximum (VBM) of GDY and MoS 2, ultraviolet spectra (UPS) are conducted.GDY and MoS 2 is transferred on 100nm Au-coated Si substrate.The work function (ф) can be inferred using the equation ф= hv-E onset , where hv is the incident photon energy (21.22 eV) [15] and E onset is the onset level related to the secondary electron. [15].The calculated ф values of GDY and MoS 2 are 4.14 and 4.27 eV, respectively.Additionally, the relative valence band maximum (VBM) position compared with Fermi level (E f ) can be inferred from the cutoff of lowest binding energy, which is 0.67 eV and 1.62 eV for GDY and MoS 2 , respectively (Figure S9, Supporting The field effect mobility ( ) of GDY and MoS 2 can be extracted using the equation , where dI/dV g is the slope of the transfer curve, the applied drain voltage (V ds ), the channel length (L), the channel width (W), and Cg as SiO 2 capacitance [16] .

Figure S6 .
Figure S6.Uv-vis absorption spectra and extracted optical bandgap by Tauc-plot function of GDY.

Figure S8 .
Figure S8.Raman mapping of GDY/MoS 2 photodetector at a) D peak and b) A 1g peak.

Figure S11 .
Figure S11. Figure S11.I-V characteristic of a) GDY and b) MoS 2 under 811nm and 1064 nm laser illumination.

Figure S12 .
Figure S12.Power-dependent photocurrent I ph under 1064 nm laser source.

Figure S15 .
Figure S15.The schematic set-up for Low-noise current.

Figure S18 .
Figure S18.Energy band diagram of GDY/MoS 2 a) before and b) after illumination.

Table S1 :
Comparison table of the performance of GDY/MoS 2 photodetector with previous graphene (Gr) and TMDs-based heterostructure.