Pressure Effects on Structure and Optical Properties in Cesium Lead Bromide Perovskite Nanocrystals

Abstract

Metal halide perovskites (MHPs) are gaining increasing interest because of their extraordinary performance in optoelectronic devices and solar cells. However, developing an effective strategy for achieving the band-gap engineering of MHPs that will satisfy the practical applications remains a great challenge. In this study, high pressure is introduced to tailor the optical and structural properties of MHP-based cesium lead bromide nanocrystals (CsPbBr NCs), which exhibit excellent thermodynamic stability. Both the pressure-dependent steady-state photoluminescence and absorption spectra experience a stark discontinuity at ∼1.2 GPa, where an isostructural phase transformation regarding the Pbnm space group occurs. The physical origin points to the repulsive force impact due to the overlap between the valence electron charge clouds of neighboring layers. Simultaneous band-gap narrowing and carrier-lifetime prolongation of CsPbBr trihalide perovskite NCs were also achieved as expected, which facilitates the broader solar spectrum absorption for photovoltaic applications. Note that the values of the phase change interval and band-gap red-shift of CsPbBr nanowires are between those for CsPbBr nanocubes and the corresponding bulk counterparts, which results from the unique geometrical morphology effect. First-principles calculations unravel that the band-gap engineering is governed by orbital interactions within the inorganic Pb-Br frame through structural modification. Changes of band structures are attributed to the synergistic effect of pressure-induced modulations of the Br-Pb bond length and Pb-Br-Pb bond angle for the PbBr octahedral framework. Furthermore, the significant distortion of the lead-bromide octahedron to accommodate the Jahn-Teller effect at much higher pressure would eventually lead to a direct to indirect band-gap electronic transition. This study enables high pressure as a robust tool to control the structure and band gap of CsPbBr NCs, thus providing insight into the microscopic physiochemical mechanism of these compressed MHP nanosystems.

Pressure-induced emission of cesium lead halide perovskite nanocrystals

“…The electronic structure and optical properties of these materials are expected to show a significant dependence on pressure 11–16 . In view of this, our group has explored their pressure dependence and found, for example, that the band gap alignment of CsPbBr 3 NCs can be successfully fine-tuned via pressure 17 . In addition, Chen et al demonstrated that pressure-sintered CsPbBr 3 nanoplatelets show a 1.6-fold enhancement in photoluminescence (PL) and display longer emission lifetimes than untreated NCs 13 .…”

A Dual‐Stimuli‐Responsive Coordination Network Featuring Reversible Wide‐Range Luminescence‐Tuning Behavior

“…[11] Herein, we report an intriguing stimuli-responsive coordination network, [Cd 3 (TPPA) 2 (NDA) 3 ]·(DMF) 10 ·(H 2 O) 6 (namely, NKU-121;T PPA: tri(4-(pyridine-4-yl)phenyl)amine,N DA :2 ,6-naphthalenedicarboxylic acid, DMF: N,Ndimethylformamide), which undergoes ag radual and reversible structural deformation under either thermal or pressure stimulation. [13][14][15] Single-crystal X-ray analysis revealed that NKU-121 crystallizes in the trigonal R " 3c space group and the asymmetric unit consists of one crystallographically independent Cd 2+ ion, one 2,6-naphthalenedicarboxylic acid (NDA 2À ) ligand, and two-thirds of aTPPAm olecule.Each Cd 2+ ion is coordinated in ap entagonal-bipyramidal geometry defined by five carboxylate oxygen atoms from three NDA 2À ligands and two pyridyl nitrogen atoms from two TPPAm olecules. As aresult, the emission color of the crystal successively shifts from cyan to green upon heating and further to red upon compression, thus going beyond as imple two-color transition.…”

Mechanofluorochromic Carbon Nanodots: Controllable Pressure‐Triggered Blue‐ and Red‐Shifted Photoluminescence

“…[1a,b, 2] Meanwhile,m etal clusters and inorganic nanocrystals also exhibit PL shifts under high pressure. [3] Nevertheless,all the reported mechanofluorochromic materials are largely limited to the mono-shift in PL. Ther eports on mechanofluorochromic materials with bidirectional shifting are extremely rare.…”