Controlling the carrier polarity and concentration underlies most electronic and optoelectronic devices. However, for the intensively studied lead halide perovskites, the doping tunability is inefficient. In this work, taking CsPbBr3 as an example, it is revealed that the coexistence of metallic Pb or CsBr3/Br2, rather than the precursor ratio, can provide Pb‐rich/Br‐poor or Br‐rich/Pb‐poor chemical conditions, enabling the tunability of electrical properties from weak n‐type, intrinsic, to moderate p‐type. Experimentally, under Br2‐exposure treatment, a shift of the Fermi level as large as 1.00 eV is achieved, which is one of the highest value among all kinds of doping methods. The X‐ray detector based on the intrinsic CsPbBr3 exhibits excellent performance, with a negligible dark‐current drift of 7.1 × 10−4 nA cm−1 s−1 V−1, a low detection limit of 103.6 nGyair s−1, and a high sensitivity of 9085 μC Gyair−1 cm−2. This work provides a critical understanding and guidance for tuning the electrical properties of lead halide perovskites, which establishes good foundations for achieving intrinsic perovskite semiconductors and also constructing potential homojunction devices.
The luminescent property of 2D perovskite materials promotes their applications in light emitting diodes, phosphor powders, and scintillators. Recently, an interesting extrinsic low‐energy broadband luminescence is hotly investigated. However, the understanding of such emissions is still at the early stage. In this study, based on a modified solvent evaporation method, centimeter‐size (BDA)PbI4 (BDA = NH3C4H8NH32+) single crystals are grown which, besides the band–band emission, show a large Stokes‐shifted broadband luminescence. We find such emission can be effectively excited by sub‐gap photons and conclude defects‐induced shallow traps are the corresponding luminescence centers. Density functional theory (DFT) calculations indicate that in‐plane iodine vacancies can introduce shallow electron traps in the band gap and give rise to the broadband emission.
Recently, A2BX6‐type halide perovskite variant phosphors have been applied for white light‐emitting diodes (LEDs) due to their superior photoluminescence properties, excellent stability, and low‐cost solution‐processability. However, the reported white LEDs, particularly the all‐A2BX6 white LEDs, exhibit insufficient color rendering due to the shortage of red light. In this work, through a rational material design, a red‐emitting perovskite variant Cs2PtCl6 phosphor is developed. The synthesized Cs2PtCl6 powders exhibit a relatively narrow bandgap of 2.91 eV and an intrinsic broadband red emission centered at 670 nm, which is attributed to the triplet self‐trapped excitons associated with the Jahn−Teller‐distorted [PtCl6]2− octahedra in the excited state. Using Cs2PtCl6 as the red phosphor component, an all‐A2BX6 white LED is constructed, achieving a standard white light with a Commission Internationale de l'Eclairage chromaticity coordinate of (0.33, 0.33), a correlated color temperature of 5318 K, and a record high color rendering index of 90. This work represents a significant step toward the application of A2BX6 perovskite variant phosphors for solid‐state lighting.
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