Scalable Synthesis of a Sub-10 nm Chalcopyrite (CuFeS₂) Nanocrystal by the Microwave-Assisted Synthesis Technique and Its Application in a Heavy-Metal-Free Broad-Band Photodetector

Abstract

A heavy-metal-free chalcopyrite (CuFeS 2 ) nanocrystal has been synthesized via microwave-assisted growth. Large-scale nanocrystals with an average particle size of 5 nm are fabricated by this technique within a very short period of time without any need for organic ligands. Scanning electron microscopy study (SEM) of individual synthesis steps indicates that aggregates of nanocrystals are formed as flakes during microwave-assisted synthesis. The colloidal solution of the CuFeS 2 nanocrystal was prepared by sonicating these flakes. Transmission electron microscopy (TEM) study reveals the growth of sub-10 nm CuFeS 2 nanocrystals that are further characterized by X-ray diffraction. UV–visible absorption spectroscopic study shows that the band gap of this nanocrystal is ∼1.3 eV. To investigate the photosensitive nature of this nanocrystal, a bilayer p–n heterojunction photodetector has been fabricated using this nontoxic CuFeS 2 nanocrystal as a photoactive material and n-type ZnO as a charge-transport layer. The detectivity of this photodetector reaches above 10 12 Jones in visible and near-infrared (NIR) regions under 10 V external bias, which is significantly high for a nontoxic nanocrystal-based photodetector.

Long-Term Stable Near-Infrared–Short-Wave-Infrared Photodetector Driven by the Photothermal Effect of Polypyrrole Nanostructures

“…Detectivity (D*), as another key parameter to evaluate the performance of PDs, was also calculated by following some reference equations from previous studies. 44,45 The maximum D* for our PPy-NPs/Pt device can reach 1.1 × 10 11 Jones, which is comparable with some InGaAs PDs (D* = 1 × 10 10 −1 × 10 13 Jones) and nanostructured PDs (D* = ∼1 × 10 8 −1 × 10 14 Jones). 46−48 Compared with commercial PDs 46,48 and some NP-based ones, 10,49−52 this PPy-NPs/Pt hybrid PD is competitive in the photodetection range, responsivity, and response time, as summarized in Table 1.…”

“…A strong photoresponsivity (in Ω/W and A/W) was measured, and the maximum values reached 7.5 × 10 6 Ω/W and 1.3 A/W (Figure d). Detectivity ( D *), as another key parameter to evaluate the performance of PDs, was also calculated by following some reference equations from previous studies. , The maximum D * for our PPy-NPs/Pt device can reach 1.1 × 10 11 Jones, which is comparable with some InGaAs PDs ( D * = 1 × 10 10 –1 × 10 13 Jones) and nanostructured PDs ( D * = ∼1 × 10 8 –1 × 10 14 Jones). − Compared with commercial PDs , and some NP-based ones, ,− this PPy-NPs/Pt hybrid PD is competitive in the photodetection range, responsivity, and response time, as summarized in Table . Notably, PPy-NPs/Pt hybrid PD reveals both faster photoresponse and slightly larger photoresponsivity than PPy-NPs/thermistor PD, although the size of the Pt pattern is much smaller than that of the NTC thermistor.…”

Wavelength-Dependent Bifunctional Plasmonic Photocatalysis in Au/Chalcopyrite Hybrid Nanostructures

“…9 In the bulk, the gap between the valence band (VB) and IB has been reported as 0.63 eV; 8,9 whereas in chalcopyrite NCs, the band gap can be increased due to quantum confinement. For NCs of similar size and Cu/Fe ratios as used in this work, an optical band gap of approximately 1.4 eV was measured, 44,51,52 which we assign to the VB-IB gap. The electron excited state energy has also been determined by Mott−Schottky plots to be −0.432 V (vs NHE), which we assign to the IB position.…”

Highly Sensitive Broadband Photodetector Based on PbI2-Passivated CdS:Mn Quantum Dots with a Spectrally Flat Response

“…To the best of our knowledge, this detectivity value is comparable among the highest reported values of nanocrystal-based photodetectors (Table ). − …”