Efficient and stable inorganic lead-free halide perovskites have attracted tremendous attention for next-generation solid-state lighting. However, single perovskite phosphors with strong, tunablecolor-temperature white-light emission are rare. Here, a doping strategy was developed to incorporate Sb 3+ and Bi 3+ ions into Cs 2 NaInCl 6 single crystals. Blue and yellow emission for white light with a 77% quantum yield was observed. The dual-emission originates from different [SbCl 6 ] 3− octahedron-related self-trapped excitons (STEs). The blue emission is attributable to limited Jahn−Teller deformation from Sb 3+ doping. Largeradii Bi 3+ increase the deformation level of the [SbCl 6 ] 3− octahedron, enhancing yellow STE emission. Density functional theory calculations indicated that the Bi 3+ doping forms a sub-band level, which produces yellow STE emission. Tuning between warm and cold white light can be realized by changing the Sb 3+ /Bi 3+ doping ratio, which suggests a unique interaction mechanism between Sb 3+ and Bi 3+ dopants, as well as Bi 3+ -induced lattice distortion in double perovskites.

Sb3+ doping confers highly efficient and color-diverse broadband light emission to all-inorganic metal-halide perovskites. However, the emission mechanism is still under debate. Herein, a trace amount of Sb3+ ions (<0.1% atomic percentage) doping in the typical all-inorganic perovskites Cs2NaInCl6, Rb3InCl6, and Cs2InCl5·H2O allows universal observation of the fine structure in the photoluminescence excitation spectrum of the ns 2 electron. A lifetime mapping method was utilized to reveal the origin of broadband emission triggered by Sb3+ doping, by which various fluorescence components can be differentiated. In particular, free-exciton emission was identified at the high-energy end of the broadband emission for all three doped systems. The excitation-energy- and temperature-dependent fluorescence decay further indicates the existence and origin of self-trapped states. The observed structural and vibrational symmetry-dependent emission behaviors suggest dipole interactions can dramatically alter Stokes-shift energy and modulate the light-emitting wavelength.

Emitting wavelength of cesium copper halides can be effectively tuned by regulating the process of mechanochemical reaction firstly.

Inorganic lead-free halide perovskites with a broadband emission of self-trapped excitons (STEs) have attracted great attention in lighting applications. However, it remains a fundamental challenge to expand the display color gamut because it is difficult to individually tune the emitting proportion at different wavelengths. Herein, we employ a doping route to incorporate Sb 3+ , Er 3+ , and Ho 3+ ions into the Cs 2 NaInCl 6 , which enables multicolor emissions with narrow full width at half-maxima and high photoluminescence quantum yields (PLQYs). The blue emission (445 nm) originates from STEs in the [SbCl 6 ] 3− octahedrons, while the narrowband green (550 nm) and red (655 nm) emissions are mainly derived from the Er 3+ and Ho 3+ ions, respectively. An efficient energy transfer between multiple luminescent centers is the key point to achieve such an efficient and tunable emission. By controlling the lanthanide doping level, the emission color can be systematically modulated, and cold 10401 K (0.278, 0.286) to warm 4608 K (0.347, 0.298) adjustable white-light emission (PLQY of ∼70%) can be achieved successfully. The results provide inspiration for the material design of lead-free perovskites with efficient and tunable light-emitting properties for optoelectronic applications.

Two-dimensional (2D) transition metal dichalcogenide (TMDC) monolayers have been widely used for optoelectronic devices because of their ultrasensitivity to light detection acquired from their direct gap properties. However, the small cross-section of photon absorption in the atomically thin layer thickness significantly limits the generation of photocarriers, restricting their performance. Here, we integrate monolayer WS2 with 2D perovskites Cs2AgBiBr6, which serve as the light absorption layer, to greatly enhance the photosensitivity of WS2. The efficient charge transfer at the Cs2AgBiBr6/WS2 heterojunction is evidenced by the shortened photoluminescence (PL) decay time of Cs2AgBiBr6. Scanning photocurrent microscopy of Cs2AgBiBr6/WS2/graphene reveals that improved charge extraction from graphene leads to an enhanced photoresponse. The 2D Cs2AgBiBr6/WS2/graphene vertical heterostructure photodetector exhibits a high detectivity (D*) of 1.5 × 1013 Jones with a fast response time of 52.3 μs/53.6 μs and an on/off ratio of 1.02 × 104. It is worth noting that this 2D heterostructure photodetector can realize self-powered light detection behavior with an open-circuit voltage of ∼0.75 V. The results suggest that the 2D perovskites can effectively improve the TMDC layer-based photodetectors for low-power consumption photoelectrical applications.

No abstract

Lead‐free double perovskite Cs2AgBiBr6 has attracted significant research interests for optoelectronic applications because of its nontoxicity, inherent stability, and high detection sensitivity. In this work, the 2D Cs2AgBiBr6 with a thickness of ≈5 nm and lateral length larger than 50 µm is successfully fabricated by a space‐confined method. The fabricated ultra‐thin 2D Cs2AgBiBr6 exhibits significant advantages on photodetection, due to its enhanced light–matter interaction. Remarkably, compared with bulk Cs2AgBiBr6, 2D Cs2AgBiBr6‐based photodetectors exhibit dramatically improved optoelectronic properties including ultra‐high detectivity (D*) of 7.4 × 1014 Jones (more than ten times), photoresponsivity (R) of 54.6 A W−1 (exceeding 4.7 times), an on/off ratio of 7.4 × 104 (more than ten times), and a fast response time of ≈1.7 ms (exceeding 30 times). In addition, due to the strong photon recycling effect of Cs2AgBiBr6, optical properties in both light absorption and emission can be effectively engineered by the material thickness, which enables a tunable wavelength‐dependent photodetection. The results provide further insights on the light–matter interaction of environmentally friendly 2D perovskites related materials and shine light on their high‐performance optoelectrical applications.

Cesium lead halide perovskite (CsPbX ) nanocrystals (NCs) exhibit an excellent photoelectric performance, which is directly governed by fine-tuning of the composition and preparation of materials with a special phase structure and morphology. However, it is still facing challenges to achieve highly stable and luminescent CsPbX NCs at room temperature. Herein, we report on a novel exchange reaction, in which metal halides MX (M=Zn, Mg, Cu, or Ca; X=Cl, Br, or I) solids act as anion source to directly prepare CsPbX NCs at room temperature without any pretreatment. Introducing small amount of oleic acid or oleylamine speed up the exchange reaction through different promotion mechanisms. Oleic acid coordinates to the surface of the NCs, which increases the reaction activity, and oleylamine greatly enhances the dissolution of ZnCl . XRD and TEM tests demonstrate that the cubic phase structure and the morphology of the parent CsPbX were well preserved. Moreover, the band-gap energies and photoluminescence (PL) spectra were readily tunable over the entire visible spectral region of λ=406-685 nm. Our findings could open up the possibilities of using metal halide solids as new anion sources to prepare high-quality CsPbX NCs at room temperature.