scholarly journals Origin of unusual bandgap shift and dual emission in organic-inorganic lead halide perovskites

2016 ◽  
Vol 2 (10) ◽  
pp. e1601156 ◽  
Author(s):  
M. Ibrahim Dar ◽  
Gwénolé Jacopin ◽  
Simone Meloni ◽  
Alessandro Mattoni ◽  
Neha Arora ◽  
...  
Keyword(s):  
Density Functional ◽  
Valence Band Maximum ◽  
Dual Emission ◽  
Time Resolved ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Perovskite Materials ◽  
Halide Perovskites ◽  
Dynamics Simulations ◽  
Increasing Temperature

Emission characteristics of metal halide perovskites play a key role in the current widespread investigations into their potential uses in optoelectronics and photonics. However, a fundamental understanding of the molecular origin of the unusual blueshift of the bandgap and dual emission in perovskites is still lacking. In this direction, we investigated the extraordinary photoluminescence behavior of three representatives of this important class of photonic materials, that is, CH3NH3PbI3, CH3NH3PbBr3, and CH(NH2)2PbBr3, which emerged from our thorough studies of the effects of temperature on their bandgap and emission decay dynamics using time-integrated and time-resolved photoluminescence spectroscopy. The low-temperature (<100 K) photoluminescence of CH3NH3PbI3and CH3NH3PbBr3reveals two distinct emission peaks, whereas that of CH(NH2)2PbBr3shows a single emission peak. Furthermore, irrespective of perovskite composition, the bandgap exhibits an unusual blueshift by raising the temperature from 15 to 300 K. Density functional theory and classical molecular dynamics simulations allow for assigning the additional photoluminescence peak to the presence of molecularly disordered orthorhombic domains and also rationalize that the unusual blueshift of the bandgap with increasing temperature is due to the stabilization of the valence band maximum. Our findings provide new insights into the salient emission properties of perovskite materials, which define their performance in solar cells and light-emitting devices.

scholarly journals Photostable and Uniform CH3NH3PbI3 Perovskite Film Prepared via Stoichiometric Modification and Solvent Engineering

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 405
Author(s):  
Daocheng Hong ◽  
Mingyi Xie ◽  
Yuxi Tian
Keyword(s):  
Solar Cells ◽  
Optoelectronic Devices ◽  
Solvent Engineering ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Coverage Ratio ◽  
Fabrication Procedure ◽  
Fabrication Condition ◽  
Halide Perovskites ◽  
Photoluminescence Efficiency

Solution-processed organometal halide perovskites (OMHPs) have been widely used in optoelectronic devices, and have exhibited brilliant performance. One of their generally recognized advantages is their easy fabrication procedure. However, such a procedure also brings uncertainty about the opto-electric properties of the final samples and devices, including morphology, stability, coverage ratio, and defect concentration. Normally, one needs to find a balanced condition, because there is a competitive relation between these parameters. In this work, we fabricated CH3NH3PbI3 films by carefully changing the ratio of the PbI2 to CH3NH3I, and found that the stoichiometric and solvent engineering not only determined the photoluminescence efficiency and defects in the materials, but also affected the photostability, morphology, and coverage ratio. Combining solvent engineering and the substitution of PbI2 by Pb(Ac)2, we obtained an optimized fabrication condition, providing uniform CH3NH3PbI3 films with both high photoluminescence efficiency and high photostability under either I-rich or Pb-rich conditions. These results provide an optimized fabrication procedure for CH3NH3PbI3 and other OMHP films, which is crucial for the performance of perovskite-based solar cells and light emitting devices.

scholarly journals The dark exciton ground state promotes photon-pair emission in individual perovskite nanocrystals

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Philippe Tamarat ◽  
Lei Hou ◽  
Jean-Baptiste Trebbia ◽  
Abhishek Swarnkar ◽  
Louis Biadala ◽  
...  
Keyword(s):  
Near Infrared ◽  
Exciton State ◽  
Lead Iodide ◽  
Electron Hole ◽  
Light Emitting ◽  
Perovskite Nanocrystals ◽  
Light Emitting Devices ◽  
Optical And Electronic Properties ◽  
Wide Range ◽  
Halide Perovskites

AbstractCesium lead halide perovskites exhibit outstanding optical and electronic properties for a wide range of applications in optoelectronics and for light-emitting devices. Yet, the physics of the band-edge exciton, whose recombination is at the origin of the photoluminescence, is not elucidated. Here, we unveil the exciton fine structure of individual cesium lead iodide perovskite nanocrystals and demonstrate that it is governed by the electron-hole exchange interaction and nanocrystal shape anisotropy. The lowest-energy exciton state is a long-lived dark singlet state, which promotes the creation of biexcitons at low temperatures and thus correlated photon pairs. These bright quantum emitters in the near-infrared have a photon statistics that can readily be tuned from bunching to antibunching, using magnetic or thermal coupling between dark and bright exciton sublevels.

Excitation energy dependent switchable emission in SrZnO2 nanophosphors: XAS and luminescence studies

2020 ◽  
Vol 8 (9) ◽  
pp. 3147-3155 ◽  
Author(s):  
Manju ◽  
Megha Jain ◽  
Pargam Vashishtha ◽  
Sanjay Kumar ◽  
Parasmani Rajput ◽  
...  
Keyword(s):  
Excitation Energy ◽  
Dual Emission ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Energy Dependent

An unprecedented excitation energy dependent dual emission from SrZnO2 nanophosphors is observed, predicting its applicability for switchable light emitting devices.

scholarly journals Improvement of photoluminescence intensity and film morphology of perovskite by Ionic liquids additive

2021 ◽  
Vol 257 ◽  
pp. 03066
Author(s):  
Dongyang Shen ◽  
Chengzhao Luo ◽  
Ronghong Zheng ◽  
Qinyi Li ◽  
Yu Chen
Keyword(s):  
Ionic Liquid ◽  
Radiative Recombination ◽  
Photoluminescence Intensity ◽  
Light Emitting ◽  
The Past ◽  
Perovskite Materials ◽  
New Strategy ◽  
Halide Perovskites ◽  
Significant Attention ◽  
Long Chain

Metal halide perovskites have received much attention for their application in light-emitting diodes (LEDs) and solar cells in the past several years. Among them, 2D and quasi-2D perovskite with organic long-chain cations introduced have drawn significant attention. However, while improving wet and thermal stability, as the grain size becomes smaller, more defects introduced at the grain boundary and surface, resulting in the increase of non-radiative recombination is becoming the main problem which should be faced by 2D/quasi-2D perovskite materials. Here, we report a new strategy employing ionic liquid named 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide(EMB).By adding a small amount of ionic liquid to the precursor, the defect was effectively passivated and the photoluminescence intensity was increased by 11 times and the fluorescent lifetime was increased by about 1.5 times. The flatness of the prepared perovskite thin films has also been effectively improved.

scholarly journals Investigation of Energy Transfer in Star-Shaped White Polymer Light-Emitting Devices via the Time-Resolved Photoluminescence

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1719 ◽  
Author(s):  
Hui He ◽  
Xiaoqing Liao ◽  
Jiang Cheng ◽  
Ying Li ◽  
Junsheng Yu ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Current Efficiency ◽  
Intermolecular Interactions ◽  
Efficient Energy Transfer ◽  
Time Resolved ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Efficient Energy ◽  
Polymer Light Emitting Devices ◽  
Time Resolved Photoluminescence

A series of white polymer light-emitting devices (WPLEDs) were fabricated by utilizing star-shaped white-emission copolymers containing tri[1-phenylisoquinolinato-C2,N]iridium (Ir(piq)3), fluorenone (FO) and poly(9,9-dioctylfluorene) (PFO) as red-, green- and blue-emitting (RGB) components, respectively. In these WPLEDs, a maximum current efficiency of 6.4 cd·A−1 at 20 mA·cm−2 and Commission Internationale d’Eclairage (CIE) coordinates of (0.33, 0.32) were achieved, and the current efficiency was still kept to 4.2 cd·A−1 at the current density of 200 mA·cm−2. To investigate energy transfer processes among the three different chromophores of the star-shaped copolymers in these WPLEDs, the time-resolved photoluminescence (PL) spectra were recorded. By comparing the fluorescence decay lifetimes of PFO chromophores in the four star-like white-emitting copolymers, the efficient energy transfer from PFO units to Ir(piq)3 and FO chromophores was confirmed. From time-resolved PL and the analysis of energy transfer process, the results as follows were proved. Owing to the star-like molecular structure and steric hindrance effect, intermolecular interactions and concentrations quenching in the electroluminescence (EL) process could also be sufficiently suppressed. The efficient energy transfer also reduced intermolecular interactions’ contribution to the enhanced device performances compared to the linear single-polymer white-light systems. Moreover, saturated stable white emission results from the joint of energy transfer and trap-assisted recombination. This improved performance is expected to provide the star-like white-emitting copolymers with promising applications for WPLEDs.

scholarly journals Luminescence control in hybrid perovskites and their applications

2017 ◽  
Vol 5 (17) ◽  
pp. 4098-4110 ◽  
Author(s):  
Josep Albero ◽  
Hermenegildo García
Keyword(s):  
Metal Halide ◽  
Luminescence Properties ◽  
Light Emitting ◽  
Composition Design ◽  
Light Emitting Devices ◽  
Halide Perovskites

Hybrid metal halide perovskites have emerged as promising photoluminescence materials in efficient light emitting devices and lasing applications. The review focus on the perovskite composition design as a tool to modulate the luminescence properties.

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