High Spectral‐Rejection‐Ratio Narrowband Photodetectors Based on Perovskite Heterojunctions

Abstract

narrowband photodetection, only narrowband optical spectra are required, whereas the background noise signal caused by the photon wavelength beyond the narrowband must be suppressed. Thus, the spectral rejection ratio narrowband spectral response wide spectra response 100% ×       is an important parameter for describing the ability of photodetectors to discriminate narrowband photons from those of wide spectra. [12][13][14][15] Typically, narrowband photodetectors rely on a combination of bulky optical filters and broadband photodetectors, which impede their less costly fabrication and miniaturization. [16,5,15] Hence, the development of nonopticalfilter narrowband photodetectors is important to miniaturization.Recently, the use of nonoptical-filter narrowband photodetectors made of MAPbX 3 perovskites have been reported in two main structures. The first is the vertical Schottky structure of Au/ MAPbX 3 perovskite single crystals (PSCs)/ (FTO,Ga), which is highly dependent on defect density differences between the MAPbX 3 PSC surface and the inside of the MAPbX 3 PSC bulk. [17,18,6,19] Owing to surface charge recombination, a surface with high density of traps can absorb short-wavelength photons, whereas the charges Narrowband photodetection provides important information in a specific wavelength range. Specially, the use of nonoptical-filter narrowband photodetectors based on MAPbX 3 (MA = CH 3 NH 3 ; X = Cl, Br, I) perovskites is reported of great potential. However, current MAPbX 3 -based narrowband photodetectors have to sacrifice their photocurrent and response speed to achieve an acceptable spectral rejection ratio. In this work, a new type of heterojunction photodetector (hetero-PD) with a structure of (n-type doped MAPbCl 3 )/(intrinsic MAPbBr 2.5 Cl 0.5 )/(n-type doped MAPbBr 3 ) via epitaxial growth is demonstrated as a narrowband photodetector. Through optical bandgap engineering, photons with different wavelength can be absorbed in different layers. Owing to the n-i-n energy band structure, most external bias would apply on a tiny region near the n-i heterojunction. Besides, the energy barriers in the heterojunctions can block holes from injection and collection, resulting in low-noise electron-only hetero-PDs. By sufficiently suppressing the background noise from short-wavelength photons, hetero-PDs are capable of achieving a high spectral rejection ratio of 98.1% under an electrical field of 8 V cm −1 . Moreover, hetero-PDs exhibit a high external quantum efficiency value of 45%, a narrow full width at half-maximum of 13 nm, and a response time of 1.35 µs.

Epitaxial Perovskite Single-Crystalline Heterojunctions for Filter-Free Ultra-Narrowband Detection with Tunable Spectral Responses

“…In addition, the optical and electronic properties of perovskite can be tuned by incorporating heterovalent ions (Bi 3+ , Ag + etc. ), which have been reported in our previous studies for fabricating high-performance photodetectors. − …”

Recent Progress on Wavelength‐Selective Perovskite Photodetectors for Image Sensing

“…Compared with polycrystalline perovskite films, perovskite single crystals without grain boundaries have many advantages, such as high carrier mobility and low volume defect density, for fabricating narrowband PDs. [61,62] Fang et al first applied perovskite single crystals (MAPbBr 3−x Cl x and MAPbI 3−x Br x , MA = CH 3 NH 3 ) to narrowband photoconductance. [63] The FWHM of spectral response ranging from blue to red was less than 20 nm.…”

Using N–I–N Photodiodes Made of Perovskite Single Crystals for Low Noise Gamma-Ray Spectroscopy

“…Two n-type layers are symmetrically deposited on the opposite sides of intrinsic MAPbX 3 LHPSCs via solutionprocessed epitaxial growth. 22,23 Subsequently, unipolar photodiodes with an NIN structure are fabricated. Because the two n-type layers only allow the transport of electrons, the injection electrons, defect-induced electrons, and photon-activated electrons can contribute to the current.…”

“…Herein, we consider the problem of intrinsic defects in solution processed LHPSCs and propose the isolation of noise from intrinsic defects inside LHPSCs by creating an energy barrier. Two n-type layers are symmetrically deposited on the opposite sides of intrinsic MAPbX 3 LHPSCs via solution-processed epitaxial growth. , Subsequently, unipolar photodiodes with an NIN structure are fabricated. Because the two n-type layers only allow the transport of electrons, the injection electrons, defect-induced electrons, and photon-activated electrons can contribute to the current.…”