Pressure-Driven Abnormal Emission Blue-Shift of Lead-Free Halide Double Perovskite Cs₂AgInCl₆ Nanocrystals

Abstract

Lead-free halide double perovskites (DPs) have been proposed as stable and promising alternatives to lead halide perovskites. Understanding the structural–optical properties of halide DPs is important for their applications. In this study, Cs2AgInCl6 DP nanocrystals, with a direct band gap, were synthesized and studied. Because of a strong electron–phonon coupling leading to exciton self-trapping, a broad emission with a large Stokes shift of Cs2AgInCl6 DP nanocrystals is observed. We observed an abnormal blue-shifted emission accompanied by a red-shifted direct absorption edge because of the reduced electron–phonon coupling under compression in the cubic phase Cs2AgInCl6 DP nanocrystals. Our study clarified the basic structural–optical correlation of halide DPs and may promote their application in related fields.

Theoretical and Experimental Advances in High-Pressure Behaviors of Nanoparticles

“…First-principles calculations illustrate that the contraction and distortion of [AgBr 6 ] 5– and [BiBr 6 ] 3– octahedra contribute to the observed band gap evolution under pressure. Experiments carried out by Li et al show an abnormal PL emission blueshift accompanied by the absorption edge redshift under pressure for Cs 2 AgInCl 6 NCs . The pressure-induced abnormal emission can be attributed to the decreased lattice relaxation energy and reduced electron–phonon coupling under compression.…”

“…287 As the pressure increases, the absorption edge of the NCs first red-shifts up to 2.0 GPa, then blue-shifts up to 15 GPa with a stark blue jump observed at 4.5 GPa. First-principles calculations illustrate that the contraction and distortion of [AgBr 6 ] 5− and [BiBr 6 ] 3− octahedra contribute 288 The pressure-induced abnormal emission can be attributed to the decreased lattice relaxation energy and reduced electron−phonon coupling under compression. In summary, pressure treatment has been demonstrated to be an efficient method to modulate the structure and optoelectronic properties of nano-MHPs, from conventional 3D MHPs to lower-dimension perovskites.…”

Temperature-Dependent Structure–Property Relationship of Mn-Doped Cs2AgInCl6 Thin Films Impacts Its Application as a Self-Powered UV Photodetector

“…Lead-free halide double perovskites (DPs) are a great addition to this class of materials due to their ability to overcome concerns related to toxicity and stability. By substituting the bivalent Pb 2+ cations with heterovalent (mono and trivalent) cations, DPs achieved enhanced stability and nontoxicity in their chemical structure A 2 B I B III X 6 . , Early reports on DPs such as Cs 2 AgBiBr 6 , Cs 2 AgSbCl 6 , and Cs 2 CuSbCl 6 suggested their suitability for optoelectronic devices such as light emitting diodes (LEDs), photodetectors, photocatalysts, and photovoltaics. − However, their indirect bandgap, , leads to inferior optoelectronic device performance. − Out of all these DP materials, Cs 2 AgInCl 6 (CAIC) has demonstrated a direct bandgap with optimal optoelectronic characteristics, including long carrier lifetimes, good moisture, light, and heat stability. − …”

Pressure-Induced Distinct Self-Trapped Exciton Emission in Sb3+-Doped Cs2NaInCl6 Double Perovskite

“…They are distinguished by durable stability, environmentally friendly attributes, and wide range of optical properties achieved through the flexible manipulation of component combinations. [1][2][3][4][5][6] Nevertheless, the majority of HDPs often demonstrate low photoluminescence quantum yields (PLQYs) due to the presence of dark self-trapped excitons (STEs), a consequence of either the indirect band gap or the parity-forbidden transition. Doping proves to be an effective strategy in enhancing the photoluminescence (PL) properties by modifying the local symmetry and relaxing the parity-forbidden exciton recombination.…”