Regulating off-centering distortion maximizes photoluminescence in halide perovskites

Abstract

Metal halide perovskites possess unique atomic and electronic configurations that endow them with high defect tolerance and enable high-performance photovoltaics and optoelectronics[1–3]. Perovskite light-emitting diodes have achieved an external quantum efficiency of over 20%[4–5]. Despite tremendous progress, fundamental questions remain, such as how structural distortion affects the optical properties. Addressing their relationships is considerably challenging due to the scarcity of effective diagnostic tools during structural and property tuning as well as the limited tunability achievable by conventional methods. Here, using pressure and chemical methods to regulate the metal off-centering distortion, we demonstrate the giant tunability of photoluminescence (PL) in both the intensity (>20 times) and wavelength (>180 nm/GPa) in the highly-distorted halide perovskites [CH3NH3GeI3, HC(NH2)2GeI3, and CsGeI3]. Using advanced in situ high-pressure probes and first-principles calculations, we quantitatively reveal a universal relationship whereby regulating the level of off-centering distortion towards 0.2 leads to the best PL performance in the halide perovskites. By applying this principle, intense PL can still be induced by substituting CH3NH3+ with Cs+ to control the distortion in (CH3NH3)1-xCsxGeI3, where the chemical substitution plays a similar role as external pressure. The compression of a fully substituted sample of CsGeI3 further tunes the distortion to the optimal value at 0.7 GPa, which maximizes the emission with a ten-fold enhancement. This work not only demonstrates a quantitative relationship between structural distortion and PL property of the halide perovskites but also illustrates the use of knowledge gained from high-pressure research to achieve the desired properties by ambient methods.

Enhanced Photoluminescence and Photoresponsiveness of Eu3+ Ions‐Doped CsPbCl3 Perovskite Quantum Dots under High Pressure

“…For the past few years, interest in high‐pressure research on halide perovskite materials has increased significantly. [ 16–18 ] Various pressure effects have been observed in halide perovskites, such as band gap modulation, pressure‐induced emission, [ 19–22 ] piezochromism, [ 23,24 ] and metallization. [ 25–27 ] The common features of photoluminescence (PL) of halide perovskites under high pressure are summarized as follows.…”

Metal cation s lone-pairs increase octahedral tilting instabilities in halide perovskites

“…We expect these lone-pair driven structural instabilities discovered in CsMBr 3 also prevail in their organic HP counterparts, which are more widely used in photovoltaics. 76…”

Harvesting Cool Daylight in Hybrid Organic–Inorganic Halides Microtubules through the Reservation of Pressure‐Induced Emission

“…demonstrated that an optimal distortion in metal halide perovskites is preferred to determine the PIE. [ 26,28–30 ] In addition, Li et al. reported an irreversible phase transition of acetamidinium nitrate by introducing CH 3 to impart steric hindrance, thus increasing the potential barrier of phase transition to stabilize the high‐pressure phase.…”