Accurate Wavelength Tracking by Exciton Spin Mixing

Abstract

for various fields of application, such as chemical material analysis, characterization of light sources, or calibration of monochromators and laser sources. Established techniques for realizing wavelength-selective light detection use one of two primary approaches: first, wavelength separation by an auxiliary structure, [1] i.e., a filter array or grating, where narrow light bands are directed onto individual pixels of a photodetector (PD) (array) with a broadband response; second, wavelength separation by the photoactive part itself, achieved by a multilayer arrangement of detectors, where every single detector is sensitive to a specific wavelength band. [2,3] Such spectroscopic devices commonly comprise solid hardware components that restrict them from versatile integration.Recent developments, however, demonstrate both the huge drive and great potential in terms of easy-to-integrate, low-cost, or lightweight applications, [4] e.g., narrowband photodiodes, [5][6][7] voltage-tunable Fabry-Pérot micro-interferometers, [8] or broadband sensors requiring wavelength multiplexing. [9] A smart approach to significantly reduce the device complexity was presented by Gautam et al. [10] A single-pixel and single-layer device was used to achieve a wavelength-sensitive photocurrent response that can discriminate red, green, and blue (RGB) values via the polarization of a polymer film in an aqueous surrounding. Only recently, a system was presented that consists of a multilayer single pixel of graded-bandgap perovskites evoking a wavelength-sensitive photocurrent response. [11] Here, we present a single-chip wavelength sensor that exploits the dynamics of singlet and triplet states to discriminate a certain input signal. We employ a solution-processed host-guest system comprising organic room-temperature phosphors and fluorescent colloidal quantum dots (QDs), thereby introducing a new, promising application for organic room-temperature phosphorescence (RTP). The latter has been put to multifaceted use, [12] such as programmable luminescent tags, [13] oxygen sensing, [14] or moisture sensing. [15] Owing to their unique scalable optical properties, high quantum yield, and elevated photostability, colloidal quantum dots proved themselves valuable in a myriad of applications, like light-emitting diodes (LEDs), [16,17] solar cells, [18][19][20] or transistors. [21,22] Here, we present a single-layer approach that turns wavelength information into a distinct photocurrent response with a spectral resolution down to 1 nm and below while covering a wavelength range from 300 to 410 nm.Wavelength-discriminating systems typically consist of heavy benchtop-based instruments, comprising diffractive optics, moving parts, and adjacent detectors. For simple wavelength measurements, such as lab-on-chip light source calibration or laser wavelength tracking, which do not require polychromatic analysis and cannot handle bulky spectroscopy instruments, lightweight, easyto-process, and flexible single-pixel devices are attracting increasing atten...

Molecular design, synthesis, properties, and applications of organic triplet emitters exhibiting blue, green, red and white room-temperature phosphorescence

“…Compound BP-2TA demonstrates a P2F value of 21. The same group 104 proposed an interesting application of BP-2TA as the active material of organic thin-film wavelength sensors for accelerating wavelength tracking of inorganic light-emitting diodes under heating. Such applications of BP-2TA were also possible due to its P2F parameter, resulting in the production of mostly triplet excited states due to efficient ISC under absorption of irradiation.…”

Tuning Charge-Transfer States by Interface Electric Fields

“…These CT excitons are commonly lower in energy than the localized excitons (LE) of the neat bulk materials, which enables the fabrication of organic devices with an optical gap below the neat-material optical gap. , For specific D–A combinations, CT states can efficiently generate charge carriers upon illumination or yield significant light emission in electroluminescent (EL) applications. These properties, used in intra- or intermolecular CT-state configurations, are employed in narrowband organic photodetectors (OPDs), , light-emitting electrochemical cells (LECs), − and organic light-emitting diodes (OLEDs), − and govern the open-circuit voltage of organic photovoltaics (OPV). − They can also promote triplet harvesting in organic phosphors, used for photoluminescent tags, oxygen, and wavelength sensors. , In the field of light-emitting devices, CT-state radiation is often referred to as exciplex emission . Regardless of whether the CT-state manifold constitutes the core of the device functionality or may be appointed a culprit for limited performance, its properties are of vital interest to all of the above applications.…”

“… 11 − 14 They can also promote triplet harvesting in organic phosphors, used for photoluminescent tags, 15 oxygen, and wavelength sensors. 16 , 17 In the field of light-emitting devices, CT-state radiation is often referred to as exciplex emission. 1 Regardless of whether the CT-state manifold constitutes the core of the device functionality or may be appointed a culprit for limited performance, its properties are of vital interest to all of the above applications.…”

Photosensitive Dielectric 2D Perovskite Based Photodetector for Dual Wavelength Demultiplexing

“…Wavelengthmultiplexed optical signals can therefore be detected with one single photovoltaic detector by simultaneously recognizing the transient spike response and normal continuous response. Compared with previously reported multispectral detectors achieved with voltage modulating, bidirectional photocurrent distinguishing, and afterglow tracking, [29][30][31][32][33] we provide a novel strategy to identify the illumination wavelengths based on the bi-functional 2D perovskite. Using the method, a dualband optical parallel communication with two-wavelength demultiplexing is demonstrated.…”