Growth of Ultraflat PbI₂ Nanoflakes by Solvent Evaporation Suppression for High‐Performance UV Photodetectors

Abstract

Optoelectronic device research is experiencing a rapid development and has been attracting a great deal of attentions from both academia and industry. As one of the most important devices in optoelectronic system, photodetectors are widely used in flame and environmental monitoring, night vision, communication, and imaging ascribing to their ability to convert optical signal to electrical signal sensitively and accurately. Driven by the Moore's Law, the feature size of the highly integrated electronic devices is approaching to several nanometers level in recent years, [1,2] which makes it urgent to exploit photodetectors with equivalent size in order to construct highly integrated and compatible photodetection system. However, when the size of a photodetector is reduced to the optical diffraction limit (less than or equal to the wavelength of incident light), the performance of the photodetector would be deteriorated 2D lead iodide (PbI 2 ) is attracting great interest due to its great potential in the application of UV photodetectors. In this work, a facile solution-based method is developed to synthesize ultraflat PbI 2 nanoflakes for high-performance UV photodetectors. By maintaining at proximate room temperature and adding an evaporation suppression solvent for slow-rate crystal growth, high-quality PbI 2 nanoflakes with an ultraflat surface are obtained. The UV photodetectors based on 2D PbI 2 nanoflakes exhibit a high photoresponsivity of 0.51 A W −1 , a high detectivity of 4.0 × 10 10 Jones, a high external quantum efficiency (EQE) of 168.9%, and a rapid response speed including a rise time of 14.1 ms and a decay time of 31.0 ms. The balanced and excellent photodetector performance of these devices paves the road for practical UV photodetection based on 2D PbI 2 nanoflakes.

Recent Progress of Heterojunction Ultraviolet Photodetectors: Materials, Integrations, and Applications

“…c) TEM image of 2D PbI 2 and current–time ( I–t ) measurement at V ds = 5 V on PbI 2 ‐based photodetector under different power densities of a 375 nm laser. Reproduced with permission 73. Copyright 2019, Wiley‐VCH.…”

“…As its layer number changes, the bandgap of a PbI 2 nanoflake varies from 2.38 to 2.5 eV. With a direct bandgap and a higher light absorbance capability, multilayered PbI 2 is favorable for constructing UV photodetectors 73…”

Programmable Single‐Crystalline PbI2 Microplate Arrays and Their Organic/Inorganic Heterojunctions

“…As shown in the bottom inset of Figure 2c, the energy disperses spectroscopy (EDS) spectra are explored to check the (Figure 2f), including E g (71 cm −1 ), A 1g (93 cm −1 ), and A u (111 cm −1 ), in line with the previous report, indicating its pure composition and high crystal quality. [36] The UV-vis absorbance and photoluminescence (PL) spectra of PbI 2 microplate arrays display a small Stokes shift and a strong emission peak at 510 nm ( Figure S9, Supporting Information). The simulated energy band diagram of PbI 2 single crystals demonstrated that multilayer PbI 2 is a direct bandgap semiconductor with a bandgap of 2.4 eV ( Figure S10, Supporting Information), which could validate spectral results.…”

Space‐Confined Growth of 2D InI Showing High Sensitivity in Photodetection

“…Metal halide semiconductors such as PbI 2 , HgI 2 , and TlBr are usually wide bandgap materials with soft lattices predisposed to defective formations. [ 10–14 ] Recently, several metal halides have been found to be excellent optoelectronic materials in the application for photovoltaic cells, [ 15,16 ] light‐emitting diodes (LEDs), [ 17,18 ] and photodetectors. [ 19,20 ] However, most of these halides show poor stability and poisonous, which have hindered their potential application in electronics and optoelectronics.…”