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InCrP:Zn was prepared using the implantation with Cr concentrations of 0.3% and 0.7%, respectively. It was confirmed that the photoluminescence peaks near 0.85(D, Cr) eV and 0.96(e,Cr) eV were Cr-correlated PL bands by the implantation of Cr. Especially, each 0.85(D, Cr) eV and 0.96(e,Cr) eV peaks were separately observed based on InP. In triple-axis x-ray diffraction patterns, the samples revealed a shoulder peak indicative of intrinsic InCrP. Ferromagnetic hysteresis loops measured at 10 K and 300 K were observed and the temperature-dependent magnetization showed ferromagnetic behavior ≥300 K, which reveals obvious and enhanced ferromagnetic spin coupling mediated by hole. [ABSTRACT FROM AUTHOR]

Multicolor tunable upconversion nanoparticles (UCNPs) have garnered attention owing to their diverse applications such as displays, imaging, and security. Typically, achieving multicolor emission from UCNPs requires complicated core/multishell nanostructures comprising a core with at least five shells. Here, we propose a strategy to achieve bright and orthogonal red (R), green (G), and blue (B) upconversion (UC) luminescence without synthesizing complicated core/quintuple-shell or core/sextuple-shell nanostructures. For achieving bright and orthogonal RGB triprimary color UC luminescence, orthogonal bicolor-emitting core/shell-structured UCNPs are synthesized and blended. Orthogonal RB, RG, and GB luminescence are achieved through photon blocking. The combination of two orthogonal bicolor-emitting UCNPs exhibits pure RGB UC luminescence and full-color tunability via manipulation of excitation laser conditions. Furthermore, we present color displays achieved with transparent UCNP-polymer composites utilizing three distinct near-infrared light wavelengths, implying that the proposed strategy for attaining RGB UC luminescence may facilitate advancements in the development of full-color volumetric displays.

High-performance chiroptical synaptic phototransistors are successfully demonstrated using heterojunctions composed of a self-assembled nanohelix of a π-conjugated molecule and a metal oxide semiconductor. To impart strong chiroptical activity to the device, a diketopyrrolopyrrole-based π-conjugated molecule decorated with chiral glutamic acid is newly synthesized; this molecule is capable of supramolecular self-assembly through noncovalent intermolecular interactions. In particular, nanohelix formed by intertwinded fibers with strong and stable chiroptical activity in a solid-film state are obtained through hydrogen-bonding-driven, gelation-assisted self-assembly. Phototransistors based on interfacial charge transfer at the heterojunction from the chiroptical nanohelix to the metal oxide semiconductor show excellent chiroptical detection with a high photocurrent dissymmetry factor of 1.97 and a high photoresponsivity of 218 A W -1 . The chiroptical phototransistor demonstrates photonic synapse-like, time-dependent photocurrent generation, along with persistent photoconductivity, which is attributed to the interfacial charge trapping. Through the advantage of synaptic functionality, a trained convolutional neural network successfully recognizes noise-reduced circularly polarized images of handwritten alphabetic characters with better than 89.7% accuracy., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Herein, we demonstrate video-rate color three-dimensional (3D) volumetric displays using elemental-migration-assisted full-color-tunable upconversion nanoparticles (UCNPs). In the heavily doped NaErF 4 :Tm-based core@multishell UCNPs, erbium migration was observed. By tailoring this migration through adjustment of the intermediate shell thickness between the core and the sensitizer-doped second shell, red-green orthogonal upconversion luminescence (UCL) was achieved. Furthermore, highly efficient red-green-blue orthogonal UCL and full-color tunability were achieved in the UCNPs through a combination of elemental-migration-assisted color tuning and selective photon blocking. Finally, 3D volumetric displays were fabricated using a UCNP-polydimethylsiloxane composite. More specifically, 3D color images were created and motion pictures based on the expansion, rotation, and up/down movement of the displayed images were realized in the display matrix. Overall, our study provides new insights into upconversion color tuning and the achievement of motion pictures in the UCNP-polydimethylsiloxane composite is expected to accelerate the further development of solid-state full-color 3D volumetric displays.

Chiral perovskites have emerged as promising candidates for polarization-sensing materials. Despite their excellent chiroptical properties, the nature of their multiple-quantum-well structures is a critical hurdle for polarization-based and spintronic applications. Furthermore, as the origin of chiroptical activity in chiral perovskites is still illusive, the strategy for simultaneously enhancing the chiroptical activity and charge transport has not yet been reported. Here, we demonstrated that incorporating a Lewis base into the lattice can effectively tune the chiroptical response and electrical properties of chiral perovskites. Through solid-state nuclear magnetic resonance spectroscopic measurements and theoretical calculations, it was demonstrated that the material property manipulation resulted from the change in the time-averaged structure induced by the Lewis base. Finally, as a preliminary proof of concept, a vertical-type circularly polarized light photodetector based on chiral perovskites was developed, exhibiting an outstanding performance with a distinguishability of 0.27 and a responsivity of 0.43 A W -1 .

Chiral perovskites are being extensively studied as a promising candidate for spintronic- and polarization-based optoelectronic devices due to their interesting spin-polarization properties. However, the origin of chiroptical activity in chiral perovskites is still unknown, as the chirality transfer mechanism has been rarely explored. Here, through the nano-confined growth of chiral perovskites (MBA 2 PbI 4(1-x) Br 4x ), we verified that the asymmetric hydrogen-bonding interaction between chiral molecular spacers and the inorganic framework plays a key role in promoting the chiroptical activity of chiral perovskites. Based on this understanding, we observed remarkable asymmetry behavior (absorption dissymmetry of 2.0 × 10 -3 and anisotropy factor of photoluminescence of 6.4 × 10 -2 for left- and right-handed circularly polarized light) in nanoconfined chiral perovskites even at room temperature. Our findings suggest that electronic interactions between building blocks should be considered when interpreting the chirality transfer phenomena and designing hybrid materials for future spintronic and polarization-based devices., (© 2022. The Author(s).)

We fabricated a 1 × 10 PbS QD photodiode array with multiple stacked QD layers with high-resolution patterning using a customized photolithographic process. The array showed the average responsivity of 5.54 × 10 -3 A/W and 1.20 × 10 -2 A/W at 0 V and -1 V under 1310- nm short-wavelength infrared (SWIR) illumination. The standard deviation of the pixel responsivity was under 10%, confirming the uniformity of the fabrication process. The response time was 2.2 ± 0.13 ms, and the bandwidth was 159.1 Hz. A prototype 1310-nm SWIR imager demonstrated that the QD photodiode-based SWIR image sensor is a cost-effective and practical alternative for III-V SWIR image sensors.

The effect of chemical-composition modification on the chiroptical property of chiral organic ammonium cation-containing organic inorganic hybrid perovskite (chiral OIHP) is investigated. Varying the mixing ratio of bromide and iodide anions in S - or R -C 6 H 5 CH 2 (CH 3 )NH 3 ) 2 PbI 4(1- x ) Br 4 x modifies the band gap of chiral OIHP, leading to a shift of the circular dichroism (CD) signal from 495 to 474 nm. However, it is also found that an abrupt crystalline structure transition occurs, and the CD signal is turned off when iodide-determinant phases are transformed into the bromide-determinant phase. To obtain CD in the wavelength range where the bromide-determinant phase is supposed to exhibit chiroptical activity, that is, <474 nm, S - or R -C 12 H 7 CH 2 (CH 3 )NH 3 with a larger spacer group can be adopted; thus, the CD signal can be further blue-shifted to ∼375 nm. Here, we show that chemical-composition modification of chiral OIHP affects the chiroptical properties of chiral OIHP in two ways: (1) tuning the wavelength of CD by modulating the excitonic band structure and (2) switching the CD on and off by inducing a crystalline-structure change. These properties can be utilized for structural engineering of high-performance chiroptical materials for spin-polarized light-emitting devices and polarization-based optoelectronics.

Two-dimensional (2D) van der Waals (vdW) heterostructures herald new opportunities for conducting fundamental studies of new physical/chemical phenomena and developing diverse nanodevice applications. In particular, vdW heterojunction p-n diodes exhibit great potential as high-performance photodetectors, which play a key role in many optoelectronic applications. Here, we report on 2D MoTe 2 /MoS 2 multilayer semivertical vdW heterojunction p-n diodes and their optoelectronic application in self-powered visible-invisible multiband detection and imaging. Our MoTe 2 /MoS 2 p-n diode exhibits an excellent electrical performance with an ideality factor of less than 1.5 and a high rectification (ON/OFF) ratio of more than 10 4 . In addition, the photodiode exhibits broad spectral photodetection capability over the range from violet (405 nm) to near-infrared (1310 nm) wavelengths and a remarkable linear dynamic range of 130 dB within an optical power density range of 10 -5 to 1 W/cm 2 in the photovoltaic mode. Together with these favorable static photoresponses and electrical behaviors, very fast photo- and electrical switching behaviors are clearly observed with negligible changes at modulation frequencies greater than 100 kHz. In particular, inspired by the photoswitching results for periodic red (638 nm) and near-infrared (1310 nm) illumination at 100 kHz, we successfully demonstrate a prototype self-powered visible-invisible multiband image sensor based on the MoTe 2 /MoS 2 p-n photodiode as a pixel. Our findings can pave the way for more advanced developments in optoelectronic systems based on 2D vdW heterostructures.

In this study, we proposed a strategy to fabricate vertically stacked subpixel (VSS) micro-light-emitting diodes (μ-LEDs) for future ultrahigh-resolution microdisplays. At first, to vertically stack the LED with different colors, we successfully adopted a bonding-interface-engineered monolithic integration method using SiO2/SiNx distributed Bragg reflectors (DBRs). It was found that an intermediate DBR structure could be used as the bonding layer and color filter, which could reflect and transmit desired wavelengths through the bonding interface. Furthermore, the optically pumped μ-LED array with a pitch of 0.4 μm corresponding to the ultrahigh-resolution of 63 500 PPI could be successfully fabricated using a typical semiconductor process, including electron-beam lithography. Compared with the pick-and-place strategy (limited by machine alignment accuracy), the proposed strategy leads to the fabrication of significantly improved high-density μ-LEDs. Finally, we systematically investigated the effects of surface traps using time-resolved photoluminescence (TRPL) and two-dimensional simulations. The obtained results clearly demonstrated that performance improvements could be possible by employing optimal passivation techniques by diminishing the pixel size for fabricating low-power and highly efficient microdisplays.

In this study, multicolor photodetectors (PDs) fabricated by using bulk p-i-n-based visible GaAs and near-infrared InGaAs structures were monolithically integrated through a high-throughput epitaxial lift-off (ELO) process. To perform multicolor detection in integrated structures, GaAs PDs were transferred onto InGaAs PDs by using a Y 2 O 3 bonding layer to simultaneously detect visible and near-infrared photons and minimize the optical loss. As a result, it was found that the GaAs top PD and InGaAs bottom PD were vertically aligned without tilting in x-ray diffraction (XRD) measurement. A negligible change in the dark currents for each PD was observed in comparison with reference PDs through electrical characterization. Furthermore, through optical measurements and simulation, photoresponses were clearly revealed in the visible and near-infrared band for the material's absorption region, respectively. Finally, we demonstrated the simultaneous multicolor detection of the visible and near-infrared region,which implies individual access to each PD without mutual interference. These results are a significant improvement for the fabrication of multicolor PDs that enables the formation of bulk-based multicolor PDs on a single substrate with a high pixel density and nearly perfect vertical alignment for high-resolution multicolor imaging.

With ever-growing technological demands in the imaging sensor industry for autonomous driving and augmented reality, developing sensors that can satisfy not only image resolution but also the response speed becomes more challenging. Herein, the focus is on developing a high-speed photosensor capable of obtaining high-resolution, high-speed imaging with colloidal quantum dots (QDs) as the photosensitive material. In detail, high-speed QD photodiodes are demonstrated with rising and falling times of τ r = 28.8 ± 8.34 ns and τ f = 40 ± 9.81 ns, respectively, realized by fast separation of electron-hole pairs due to the action of internal electric field at the QD interface, mainly by the interaction between metal oxide and the QD's ligands. Such energy transfer relations are analyzed and interpreted with time-resolved photoluminescence measurements, providing physical understanding of the device and working principles., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We found that optical Aharonov-Bohm oscillations in a single GaAs/GaAlAs quantum ring can be controlled by excitation intensity. With a weak excitation intensity of 1.2 kW cm -2 , the optical Aharonov-Bohm oscillation period of biexcitons was observed to be half that of excitons in accordance with the period expected for a two-exciton Wigner molecule. When the excitation intensity is increased by an order of magnitude (12 kW cm -2 ), a gradual deviation of the Wigner molecule condition occurs with decreased oscillation periods and diamagnetic coefficients for both excitons and biexcitons along with a spectral shift. These results suggest that the effective orbit radii and rim widths of electrons and holes in a single quantum ring can be modified by light intensity via photoexcited carriers, which are possibly trapped at interface defects resulting in a local electric field.

We report on the growth and optical characterization of droplet GaAs quantum dots (QDs) with extremely-thin (11 nm) capping layers. To achieve such result, an internal thermal heating step is introduced during the growth and its role in the morphological properties of the QDs obtained is investigated via scanning electron and atomic force microscopy. Photoluminescence measurements at cryogenic temperatures show optically stable, sharp and bright emission from single QDs, at visible wavelengths. Given the quality of their optical properties and the proximity to the surface, such emitters are good candidates for the investigation of near field effects, like the coupling to plasmonic modes, in order to strongly control the directionality of the emission and/or the spontaneous emission rate, crucial parameters for quantum photonic applications.

SiO 2 is a commonly used insulation layer for QCLs but has high absorption peak around 8 to 10 µm. Instead of SiO 2 , we used Y 2 O 3 as an insulation layer for DC-QCL and successfully demonstrated lasing operation at the wavelength around 8.1 µm. We also showed 2D numerical analysis on the absorption coefficient of our DC-QCL structure with various parameters such as insulating materials, waveguide width, and mesa angle.

Although various colloidal quantum dot (QD) coating and patterning techniques have been developed to meet the demands in optoelectronic applications over the past years, each of the previously demonstrated methods has one or more limitations and trade-offs in forming multicolor, high-resolution, or large-area patterns of QDs. In this study, we present an alternative QD patterning technique using conventional photolithography combined with charge-assisted layer-by-layer (LbL) assembly to solve the trade-offs of the traditional patterning processes. From our demonstrations, we show repeatable QD patterning process that allows multicolor QD patterns in both large-area and microscale. Also, we show that the QD patterns are robust against additional photolithography processes and that the thickness of the QD patterns can be controlled at each position. To validate that this process can be applied to actual device applications as an active material, we have fabricated inverted, differently colored, active QD light-emitting device (QD-LED) on a pixelated substrate, which achieved maximum electroluminescence intensity of 23 770 cd/m 2 , and discussed the results. From our findings, we believe that our process provides a solution to achieving both high-resolution and large-scale QD pattern applicable to not only display, but also to practical photonic device research and development.

We report an experimental study on the highly enhanced upconversion luminescence (UCL) of β-NaYF4:Yb(3+)/Er(3+) nanocrystals (NCs) in a plasmonic architecture. For the architecture, we designed a thin film device composed of a thin layer of NCs capped with an upper layer of a plasmonic nanodome array (pNDA) and lower substrate of a back reflector (BR). Compared to the UCL intensity observed in a glass reference substrate, the designed plasmonic architecture exhibits distinctively strong luminescence enhanced by up to 800-fold. The intensity considerably exceeds the previously reported luminescence intensity regardless of the excitation power. We elucidated a mechanism explaining the large UCL enhancement, which quantitatively analyzes the combination of plasmonic effects as well as multiple large scattering. More importantly, we provided a detailed analysis of the Ag NDA-derived and BR-assisted plasmonic effects that contribute to an increase in the radiative decay rate and an enhancement of the absorption of incident light. The present study is expected to be beneficial for designing a thin film-based plasmonic structure with a randomized metal nanostructure for high-efficiency photovoltaic devices and infrared detectors.

We describe a metal nanodisk-insulator-metal (MIM) structure that enhances lanthanide-based upconversion (UC) and downshifting (DS) simultaneously. The structure was fabricated using a nanotransfer printing method that facilitates large-area applications of nanostructures for optoelectronic devices. The proposed MIM structure is a promising way to harness the entire solar spectrum by converting both ultraviolet and near-infrared to visible light concurrently through resonant-mode excitation. The overall photoluminescence enhancements of the UC and DS were 174- and 29-fold, respectively.

This paper reports for the first time the luminescent property of polystyrene (PS), produced by pulsed ultra violet laser irradiation. We have discovered that, in air, ultra-violet (UV) irradiated PS nanospheres emit bright white light with the dominant peak at 510 nm, while in vacuum they emit in the near-blue region. From the comparison of PS nanospheres irradiated in vacuum and air, we suggest that the white luminescence is due to the formation of carbonyl groups on the surface of PS by photochemical oxidation. Our results potentially offer a new route and strategy for white light sources.