Lakshminarayana Polavarapu

Lead‐free halide double perovskites (e.g., Cs ₂ ZrCl ₆ , CZC) have attracted enormous attention in view of their nontoxic composition and high stability compared to lead‐based analogues. However, despite the near‐unity photoluminescence quantum yield (PLQY) of bulk CZC, colloidal nanocrystals (NCs) typically exhibit much weaker emission, a common limitation of double perovskite NCs arising from surface defects. Thus, the realization of highly luminescent, colloidally stable CZC NCs remains challenging. Herein, we introduce a general top‐down approach for the synthesis of brightly emissive colloidal Cs ₂ ZrCl ₆ : Te ⁴⁺ (CZCT) NCs by direct ultrasonication of bulk powders with the assistance of ligands. This ligand‐assisted ultrasonication strategy is not limited to CZCT but is potentially extendable to other structurally related lead‐free double perovskite materials (such as Cs ₂ AgInCl ₆ :Bi ³⁺ ). The obtained CZCT NCs exhibit larger lateral size (over 100 nm) and PL quantum yield up to 65%, significantly outperforming the NCs prepared by the conventional hot‐injection approach (24%). High‐resolution atomic‐level analysis indicates that the doping of Te ⁴⁺ increases the lattice strain, and Te atoms prefer to segregate inside CZCT NCs. The NC colloidal dispersion enabled solution‐processed thin films that showed a sensitive response to x‐ray irradiation, with a light yield of 42 600 ± 2300 photons/MeV and high spatial resolution imaging of 12.2 lp/mm.

Achieving nonreciprocal transmission of circularly polarized light (CPL) is critical for chiral photonics and spin‐selective optical communication, yet existing optical diodes typically operate at fixed wavelengths. Here, we report an all‐optical, photoswitchable diode‐type device for tunable nonreciprocal (asymmetric) transmission of CPL across a broad spectrum of light using molecular motor (photoswitch)‐doped cholesteric liquid crystals (CLCs) sandwiched between polyvinyl alcohol (PVA) and polydopamine (PDA)‐PVA composite layers. Under ultraviolet irradiation, the photoswitches continuously modulate the helical twisting power of the CLC, enabling reversible tuning of the photonic bandgap (PBG) and, at higher irradiation levels, helix inversion with opposite handedness. Thus, we demonstrate dynamic switching of both the operating wavelength and the isolated CPL helicity within a single device architecture. The asymmetric PDA@PVA photothermal interface enables forward photothermal activation of the cholesteric–isotropic transition while maintaining spin‐selective Bragg reflection under backward incidence. This mechanism enables wavelength‐tunable and chirality‐adaptive nonreciprocal transmission for both right‐ and left‐handed CPL. The device achieves isolation ratios exceeding 15.10 dB at all tested wavelengths, with a maximum value of 15.80 dB at 980 nm, while maintaining insertion losses below 2.89 dB, reaching as low as 1.05 dB. Furthermore, the operating thresholds and thermal tolerance can be tailored through liquid‐crystal composition.

X‐ray imaging is indispensable for medical diagnosis and non‐destructive testing. However, the optical crosstalk induced by light scattering within conventional achiral scintillator screens limits their resolution. Despite recent progress in metal halide scintillators for X‐ray imaging, achieving high resolution is still challenging. Herein, we report novel luminescent zero‐dimensional chiral manganese halides R / S ‐(TCHD) ₂ MnCl ₄ (Cl) ₂ (R/S‐(TCHD) = (1R/S,2R/S)‐N1,N1,N2,N2‐Tetramethylcyclohexane‐1,2‐diamine), which exhibit near‐unity photoluminescence quantum yield (PLQY∼99.03%) through a charge‐ transfer‐mediated mechanism. The presence of the chiral ligand induces intense circularly polarized luminescence, featuring relatively high luminescence dissymmetry factors up to 1.4 × 10 ⁻² and −1.2 × 10 ⁻² for R and S crystals, respectively. Importantly, the single crystals demonstrate X‐ray detection with a remarkable light yield of 43 380 photons/MeV and a low detection limit of 0.05198 µGy _air ·s ⁻¹ . Furthermore, the polarization sensitivity of chiral metal halides enables high‐resolution X‐ray imaging by suppressing optical crosstalk through effective filtering of scattered light. Consequently, the fabricated flexible scintillator films exhibit superior imaging capabilities with a high spatial resolution of 17.09 lp·mm ⁻¹ (∼58.5 µm per line pair), higher than the typical resolution of 5–10 lp/mm (100–200 µm) in conventional medical X‐ray imaging used in hospitals. In addition, this new class of chiral metal halide crystals exhibits broadband second harmonic generation with an efficiency higher than that of the classical KDP crystal, demonstrating the potential for a broad range of applications. This study not only presents a high‐performance chiral system for X‐ray detection but also offers an effective strategy for improving X‐ray imaging resolution by exploiting the polarization sensitivity of chiral metal halide scintillators.

With the growing importance of displays, reducing their power consumption has become crucial for developing energy‐efficient photonic–electronic platforms. Conventional light emitting diodes (LEDs) rely on external polarizers and waveplates to control light polarization in displays, but these optics cause at least half of the incident energy of the LEDs to be lost, demanding higher drive currents and accelerating degradation. Generating circularly polarized light (CPL) directly at the source offers a low‐power alternative by eliminating such optical losses and enabling direct spin–photon interfaces. Recently, chiral metal halide perovskites (MHPs) have emerged as efficient, solution‐processable semiconductors that intrinsically couple light polarization and spin. Their strong spin–orbit coupling and broken inversion symmetry enable spin‐selective charge transport via the chiral‐induced spin selectivity effect, allowing both spin manipulation and its impact on emission to be observed within the same layer. In colloidal nanocrystal form they can emit CPL with high photoluminescence quantum yield, making them promising candidates for chiral light emission, although their use is still limited by low polarization anisotropy. This perspective discusses intrinsic and extrinsic routes to achieve circularly polarized electroluminescence (CP‐EL) using chiral MHPs, highlights progress in low‐dimensional films and chiral‐ligand nanocrystals, and discusses prospects for room‐temperature spin control and filter‐free, spin‐LEDs for next‐generation energy‐efficient optoelectronic displays.

Despite growing research efforts on inorganic lead halide perovskite nanocrystals, the mechanistic understanding of nucleation and growth kinetics remains insufficient for achieving precise morphology and crystal structure control. Herein, by simply modulating the concentrations of primitive ligands ( e.g ., I ⁻ and oleylamine) into conventional synthetic strategies, CsPbI ₃ perovskites, ranging from zero‐dimensional quantum dots to unique one‐dimensional nanowires/nanorods and ginkgo leaf‐like architectures, can be realized. Mechanistic studies suggests that capping agents compete for adsorption on specific crystal facets, a finding further confirmed by density functional theory (DFT) calculations. Simultaneously, the crystal structures of the products undergo a phase transition from cubic to orthorhombic symmetry driven by lattice distortion that disrupts the crystal symmetry. In addition, temperature‐dependent photoluminescence studies revealed that the electron‐phonon coupling strengths of longitudinal optical (LO) phonons (γ _LO = 73.14 meV and = 28.74 meV) of CsPbI ₃ nanorods were much lower (γ _LO = 103.25 meV and E _LO = 33.62 meV) than those of ginkgo leaf‐like CsPbI ₃ superstructures, limiting multi‐phonon‐assisted non‐radiative pathways. As a result, CsPbI ₃ nanorods display a strong polarization dependence with a polarization degree of up to ∼0.49. These results not only demonstrates novel perovskite nanocrystals but also provide a versatile platform for tailoring perovskite NCs with combined morphological diversity and tunable optical properties.

Perovskite nanocrystals (PNCs) exhibiting circularly polarized luminescence (CPL) represent a promising class of materials for display and light communication technologies, owing to their emission covering the entire visible range with near‐unity photoluminescence efficiency. However, these materials suffer from low selectivity in the handedness of the emitted light, with most studies focusing on green emission. We address these issues by exploiting and broadening the scope of interactions between achiral PNCs and chiral organic templates. For this purpose, we select three types of PNCs with red, green, and blue emissions and introduce them into a chiral liquid‐crystalline matrix in the form of composite thin films. Electron microscopy confirmed the assembly of PNCs within nanoscale gaps formed by supramolecular, liquid crystalline structures. The obtained composites displayed a CPL dissymmetry factor g _lum up to ≈ 0.24. The highly dissymmetric CPL properties were found to result from an interplay between two effects: chiral assembly of PNCs within a chiral environment (intrinsic) and the selective filtering by the chiral matrix. This system enables control over the dominant factors by adjusting the CPL spectral region and type of particle assembly, providing thin film materials with highly dissymmetric and spectrally tunable CPL responses.

Perovskite nanocrystals (PNCs) exhibiting circularly polarized luminescence (CPL) represent a promising class of materials for display and light communication technologies, owing to their emission covering the entire visible range with near‐unity photoluminescence efficiency. However, these materials suffer from low selectivity in the handedness of the emitted light, with most studies focusing on green emission. We address these issues by exploiting and broadening the scope of interactions between achiral PNCs and chiral organic templates. For this purpose, we select three types of PNCs with red, green, and blue emissions and introduce them into a chiral liquid‐crystalline matrix in the form of composite thin films. Electron microscopy confirmed the assembly of PNCs within nanoscale gaps formed by supramolecular, liquid crystalline structures. The obtained composites displayed a CPL dissymmetry factor g _lum up to ≈ 0.24. The highly dissymmetric CPL properties were found to result from an interplay between two effects: chiral assembly of PNCs within a chiral environment (intrinsic) and the selective filtering by the chiral matrix. This system enables control over the dominant factors by adjusting the CPL spectral region and type of particle assembly, providing thin film materials with highly dissymmetric and spectrally tunable CPL responses.