Role of Intrinsic Ion Accumulation in the Photocurrent and Photocapacitive Responses of MAPbBr₃ Photodetectors

We studied steady state and transient photocurrents in thin film and single-crystal devices of MAPbBr₃, a prototype organic–inorganic hybrid perovskite. We found that the devices’ capacitance is abnormally large, which originates from accumulation of large densities of Pb²⁺ and Br^– in the active perovskite layer. Under applied bias, these ions are driven toward the opposite electrodes leading to space-charge fields close to the metal/perovskite interfaces. The ion accumulation, in turn, causes photocurrent reversal polarity that depends on the history of the applied bias and excitation photon energy with respect to the optical gap. Furthermore, the large capacitive response dominates the transient photocurrent and, therefore, obscures the weaker contribution from the photocarriers’ drift. We show that these properties depend on the ambient conditions in which the measurements are performed. Understanding these phenomena may lead to better control over the stability of perovskite photodetectors for visible light

Manipulation of Emission Colors Based on Intrinsic and Extrinsic Magneto-Electroluminescence from Exciplex Organic Light-Emitting Diodes

Exciplex organic light-emitting diodes (XOLEDs) utilize nonemissive triplet excitons via a reverse intersystem crossing process of thermally activated delayed fluorescence. The small energy difference between the lowest singlet and triplet levels of exciplex also allows a magnetic field to manipulate their populations, thereby achieving ultralarge “intrinsic” magneto-electroluminescence (MEL) in XOLEDs. Here we incorporate it into a hybrid type of spintronic device (“hybrid spin-XOLED”), where the XOLED is connected to a magnetic tunnel junction with large magnetoresistance, to introduce an “extrinsic” MEL response that interferes with the “intrinsic” MEL. The ratio between two MEL contributions, the MEL value, and the field response were altered by changing the exciplex layer thickness or actively manipulated by adding another current source that drives the XOLED. Most importantly, by involving two XOLEDs (green and red) in the same circuit, the hybrid spin-XOLED shows a color change when sweeping the magnetic field, which provides an alternative way for future OLED display technologies

Electroabsorption Spectroscopy Studies of (C₄H₉NH₃)₂PbI₄ Organic–Inorganic Hybrid Perovskite Multiple Quantum Wells

Two-dimensional (2D) organic–inorganic hybrid perovskite multiple quantum wells that consist of multilayers of alternate organic and inorganic layers exhibit large exciton binding energies of order of 0.3 eV due to the dielectric confinement between the inorganic and organic layers. We have investigated the exciton characteristics of 2D butylammonium lead iodide, (C₄H₉NH₃)₂PbI₄ using photoluminescence and UV–vis absorption in the temperature range of 10 K to 300 K, and electroabsorption spectroscopy. The evolution of an additional absorption/emission at low temperature indicates that this compound undergoes a phase transition at ≈250 K. We found that the electroabsorption spectrum of each structural phase contains contributions from both quantum confined exciton Stark effect and Franz–Keldysh oscillation of the continuum band, from which we could determine more accurately the 1s exciton, continuum band edge, and the exciton binding energy

Machine-Learning-Driven Discovery of Mn⁴⁺-Doped Red-Emitting Fluorides with Short Excited-State Lifetime and High Efficiency for Mini Light-Emitting Diode Displays

The discovery of high-efficiency Mn4+-activated fluoride red phosphors with short excited-state lifetimes (ESLs) is urgent and crucial for high-quality, wide-color-gamut display applications. However, it is still a great challenge to design target phosphors with both short ESL and high luminescence efficiency. Herein, we propose an efficient machine learning approach based on a small dataset to establish the ESL prediction model, thereby facilitating the discovery of new Mn4+-activated fluorides with short ESLs. Such a model can not only accurately predict the ESLs of Mn4+ in fluorides but also quantify the impact of structure features on ESLs, therefore elucidating the “structure-lifetime” correlations. Guided by the correlations, two new Mn4+-doped tetramethylammonium (TMA)-based hybrid fluorides (TMA)2BF6:Mn4+ (B = Sn or Hf) with both short ESLs (τ ≤ 3.7 ms) and high quantum efficiencies (internal QEs > 92%, external QEs > 55%) have been discovered successfully. A prototype displayer with excellent performance (∼124% National Television Standards Committee (NTSC) color gamut) is assembled by employing a (TMA)2SnF6:Mn4+-based white Mini-LED backlight module, demonstrating its practical prospects in high-quality displays. This work not only brings promising candidates for Mn4+-doped fluoride phosphors but also provides a valuable reference for accelerating the discovery of new promising phosphors

Machine-Learning-Driven Discovery of Mn⁴⁺-Doped Red-Emitting Fluorides with Short Excited-State Lifetime and High Efficiency for Mini Light-Emitting Diode Displays

The discovery of high-efficiency Mn4+-activated fluoride red phosphors with short excited-state lifetimes (ESLs) is urgent and crucial for high-quality, wide-color-gamut display applications. However, it is still a great challenge to design target phosphors with both short ESL and high luminescence efficiency. Herein, we propose an efficient machine learning approach based on a small dataset to establish the ESL prediction model, thereby facilitating the discovery of new Mn4+-activated fluorides with short ESLs. Such a model can not only accurately predict the ESLs of Mn4+ in fluorides but also quantify the impact of structure features on ESLs, therefore elucidating the “structure-lifetime” correlations. Guided by the correlations, two new Mn4+-doped tetramethylammonium (TMA)-based hybrid fluorides (TMA)2BF6:Mn4+ (B = Sn or Hf) with both short ESLs (τ ≤ 3.7 ms) and high quantum efficiencies (internal QEs > 92%, external QEs > 55%) have been discovered successfully. A prototype displayer with excellent performance (∼124% National Television Standards Committee (NTSC) color gamut) is assembled by employing a (TMA)2SnF6:Mn4+-based white Mini-LED backlight module, demonstrating its practical prospects in high-quality displays. This work not only brings promising candidates for Mn4+-doped fluoride phosphors but also provides a valuable reference for accelerating the discovery of new promising phosphors

Magnetic-Field-Driven Reconfigurable Microsphere Arrays for Laser Display Pixels

Reconfigurable microlaser arrays are essential to the construction of display panels where the individual pixel should be highly tunable in resonance mode, optical polarization, and lasing wavelength upon external control signals. Here we demonstrate a facile yet reliable approach to fabrication of organic microlaser pixels, in which the assembly of microsphere arrays on each pixel is controlled according to the near-field magnetostatic confinement. The geometrical configuration of diamagnetic microspheres could be readily modulated with the near-field potential traps by using the external field to alternate the saturation magnetization of the underneath micromagnet. The motion of microspheres can be modulated among several states upon applied field, and the reconfigurable microsphere array is thus achieved with high spatial precision and rapid temporal response. Moreover, both isolated and coupled spheres serve as low-threshold microlasers with tunable optical resonance modes, whereas the switching between the vertical and horizontal alignments of coupled spheres manipulates the polarization of lasing outputs. By repeating the magnetostatic confinement on the same substrate, the full-color laser display pixels with magnetically tunable color expression capability are successfully achieved

Magnetic-Field-Driven Reconfigurable Microsphere Arrays for Laser Display Pixels

Reconfigurable microlaser arrays are essential to the construction of display panels where the individual pixel should be highly tunable in resonance mode, optical polarization, and lasing wavelength upon external control signals. Here we demonstrate a facile yet reliable approach to fabrication of organic microlaser pixels, in which the assembly of microsphere arrays on each pixel is controlled according to the near-field magnetostatic confinement. The geometrical configuration of diamagnetic microspheres could be readily modulated with the near-field potential traps by using the external field to alternate the saturation magnetization of the underneath micromagnet. The motion of microspheres can be modulated among several states upon applied field, and the reconfigurable microsphere array is thus achieved with high spatial precision and rapid temporal response. Moreover, both isolated and coupled spheres serve as low-threshold microlasers with tunable optical resonance modes, whereas the switching between the vertical and horizontal alignments of coupled spheres manipulates the polarization of lasing outputs. By repeating the magnetostatic confinement on the same substrate, the full-color laser display pixels with magnetically tunable color expression capability are successfully achieved

Machine-Learning-Driven Discovery of Mn⁴⁺-Doped Red-Emitting Fluorides with Short Excited-State Lifetime and High Efficiency for Mini Light-Emitting Diode Displays

The discovery of high-efficiency Mn4+-activated fluoride red phosphors with short excited-state lifetimes (ESLs) is urgent and crucial for high-quality, wide-color-gamut display applications. However, it is still a great challenge to design target phosphors with both short ESL and high luminescence efficiency. Herein, we propose an efficient machine learning approach based on a small dataset to establish the ESL prediction model, thereby facilitating the discovery of new Mn4+-activated fluorides with short ESLs. Such a model can not only accurately predict the ESLs of Mn4+ in fluorides but also quantify the impact of structure features on ESLs, therefore elucidating the “structure-lifetime” correlations. Guided by the correlations, two new Mn4+-doped tetramethylammonium (TMA)-based hybrid fluorides (TMA)2BF6:Mn4+ (B = Sn or Hf) with both short ESLs (τ ≤ 3.7 ms) and high quantum efficiencies (internal QEs > 92%, external QEs > 55%) have been discovered successfully. A prototype displayer with excellent performance (∼124% National Television Standards Committee (NTSC) color gamut) is assembled by employing a (TMA)2SnF6:Mn4+-based white Mini-LED backlight module, demonstrating its practical prospects in high-quality displays. This work not only brings promising candidates for Mn4+-doped fluoride phosphors but also provides a valuable reference for accelerating the discovery of new promising phosphors

Machine-Learning-Driven Discovery of Mn⁴⁺-Doped Red-Emitting Fluorides with Short Excited-State Lifetime and High Efficiency for Mini Light-Emitting Diode Displays

The discovery of high-efficiency Mn4+-activated fluoride red phosphors with short excited-state lifetimes (ESLs) is urgent and crucial for high-quality, wide-color-gamut display applications. However, it is still a great challenge to design target phosphors with both short ESL and high luminescence efficiency. Herein, we propose an efficient machine learning approach based on a small dataset to establish the ESL prediction model, thereby facilitating the discovery of new Mn4+-activated fluorides with short ESLs. Such a model can not only accurately predict the ESLs of Mn4+ in fluorides but also quantify the impact of structure features on ESLs, therefore elucidating the “structure-lifetime” correlations. Guided by the correlations, two new Mn4+-doped tetramethylammonium (TMA)-based hybrid fluorides (TMA)2BF6:Mn4+ (B = Sn or Hf) with both short ESLs (τ ≤ 3.7 ms) and high quantum efficiencies (internal QEs > 92%, external QEs > 55%) have been discovered successfully. A prototype displayer with excellent performance (∼124% National Television Standards Committee (NTSC) color gamut) is assembled by employing a (TMA)2SnF6:Mn4+-based white Mini-LED backlight module, demonstrating its practical prospects in high-quality displays. This work not only brings promising candidates for Mn4+-doped fluoride phosphors but also provides a valuable reference for accelerating the discovery of new promising phosphors