Transcending the slow bimolecular recombination in lead-halide perovskites for electroluminescence

Xing, Guichuan; Wu, Bo; Wu, Xiangyang; Li, Mingjie; Du, Bin; Wei, Qi; Guo, Jia; Yeow, Edwin K. L.; Sum, Tze Chien; Huang, Wei

doi:10.1038/ncomms14558

Cited by 532 publications

(619 citation statements)

References 43 publications

(94 reference statements)

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“…The Ruddlesden-Popper type 2D perovskites consist of well-defined inorganic perovskite layers intercalated with bulky butylammonium (BA) cations acting as spacers between these fragments ( Figure 1c). [50] The excitons feature large binding energies and fast recombination within the quantum well, as validated previously. In this special multi-quantum-well structure, the carriers are therefore tightly confined in the 2D inorganic layers.…”

Section: Thickness-dependent Photoluminescence Of 2d Perovskite Platesupporting

confidence: 72%

The Dominant Energy Transport Pathway in Halide Perovskites: Photon Recycling or Carrier Diffusion?

Gan

Wen

Chen

et al. 2019

Advanced Energy Materials

104

116

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applications, such as solar cells, [1][2][3][4][5][6][7] lightemitting devices (LEDs), [8][9][10] photodetectors, [11][12][13] and lasers. [14][15][16][17] Regarding the solar cells, the diffusion of photogenerated carriers and photon recycling are the two possible energy transport pathways that could affect the internal carrier dynamics and device performances. [18][19][20][21] Both processes may cause a similar influence in the external emission wavelength. Whereas, their influences on carrier lifetime, external photoluminescence (PL) quantum yield (QY), as well as opencircuit voltage (V OC ) and efficiency of the solar cells are different. [18,19] Photon recycling refers to the regeneration of an excitation via the self-reabsorption of emission from recombining photogenerated charge pairs. [18] For solar cells, generally, the performance can be boosted by a highly efficient photon recycling process. [18][19][20][21] As demonstrated previously, photon recycling will boost an additional open-cir-) according to, [20] ln 1 1where k is the Boltzmann constant, q is the elementary charge of an electron, T C is the cell temperature, η IN is the internal quantum efficiency, and p r is the probability of photon recycling. On the other hand, for LEDs, strong photon recycling implies a low outcoupling probability (η esc ), which is detrimental for external efficiency. For example, an internal PL QY lower than 95% can result in an external PL QY lower than 50%. [18] Moreover, the photophysics behind photon recycling and carrier diffusion are different. The high photon recycling efficiency generally requires a large overlapping of its PL spectrum with the absorption spectrum, a strong photon confinement, and a high-internal PL quantum yield. [18][19][20] While long carrier diffusion length is ensured by long carrier lifetime, high carrier mobility, and low defect density. [22][23][24][25][26][27] These two energy transport pathways imply different applications, therefore, it is crucial to evaluate the contributions of photon recycling and carrier diffusion in lead halide perovskites.In perovskites, very long diffusion lengths exceeding 1 µm in solution-fabricated films and hundreds of micrometers in single crystals have been reported, [22][23][24][25][26][27] enabling the radiative recombination of charge carriers at positions far away from the excitation spot. On the other hand, due to the highly efficient band-to-band transitions, large absorption coefficients, Photon recycling and carrier diffusion are the two plausible processes that primarily affect the carrier dynamics in halide perovskites, and therefore the evaluation of the performance of their photovoltaic and photonic devices. However, it is still challenging to isolate their individual contributions because both processes result in a similar emission redshift. Herein, it is confirmed that photon recycling is the dominant effect responsible for the observed redshifted emission. By applying one-and two-photon confocal emission microscopy on Ruddlesden-Popper type ...

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Section: Thickness-dependent Photoluminescence Of 2d Perovskite Platesupporting

confidence: 72%

The Dominant Energy Transport Pathway in Halide Perovskites: Photon Recycling or Carrier Diffusion?

Gan

Wen

Chen

et al. 2019

Advanced Energy Materials

104

116

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“…As calculated, the exciton binding energy of these PNCs can increase from a few tens of meV to more than 300 meV [17,102,103] while their excitonic monomolecular recombination rates is almost two orders of magnitude higher than that of the bulk 3D counterparts. [104] Furthermore, an unusual excitation behavior for the RP structure containing PNCs with different layer numbers is discovered, instead of displaying multiple light emission peaks associated with the 2D structures upon excitation, only the emission of the PNCs with the largest n value, i.e., the smallest bandgap is observed, which is in close proximity to that of the 3D perovskite materials. An energy transfer mechanism is therefore proposed, that is, rather than self-recombination or quenching, the excitons in the PNCs with lower n values undergo a funneling effect through an energy cascade to the nanocrystal grains with the highest n, as shown in Figure 5d.…”

Section: Organic Ammonium Assisted In Situ Fabricationmentioning

confidence: 95%

In Situ Fabricated Perovskite Nanocrystals: A Revolution in Optical Materials

Chang

Bai

Zhong

2018

Advanced Optical Materials

192

127

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in bulk halide perovskites, long carrier diffusion length, and an absorption range covering the visible solar spectrum, collectively enable the high performance of photo electricity conversion. Compared to the bulk materials, perovskite nanocrystals or quantum dots (usually denoted as PNCs or PQDs) show obvious excitonic features with enhanced photoluminescence (PL) properties due to the well-known size-dependent quantum confinement effects. [14][15][16][17] The combination of color saturated emissions, super high quantum yield (QY), as well as easy processing inspired the intensive exploration of PNCs as light emitters, which is now under spotlights in the field of optical materials.The first perspective aim of PNCs is to alternate the state-of-the-art CdSe or InP quantum dots (QDs) as new generation luminescence materials. [18,19] As shown in Figure 1, these QD materials have been well demonstrated to be potential functional components for photonic and optoelectronic applications, and are currently on the way to industrialization. [20][21][22][23] Specifically, QDs can be employed as fluorescence labels, [24] laser gain media, [25] LED phosphors, [26] and down-shifting films for LCD backlights. [27,28] They can also be processed into thin film for optoelectronic devices including solar cells, [29] photodetectors, [30,31] transistors [32] and LEDs. [33] The PNCs outcompete these conventional QDs in terms of narrower full width at half maximum (FWHM) and low fabrication cost, but most importantly, the ease of in situ preparation. [34,35] Herein, this progress report highlight the developments of in situ fabricated PNCs.Colloidal semiconductor QDs are typically synthesized ex situ in flasks by hot injection method, stabilized by surface ligands. [36][37][38][39] To incorporate such solution based materials into applications usually requires purification, redispersion and surface engineering. For instance, ligand exchange is often employed to disperse QDs into aimed solvent, inducing defects that inevitably derogating the PLQYs. [40] Moreover, the organic ligands themselves also suffer from the risk of disabsorbing, reducing the stability of the QDs and thus the final devices. [41] Because halide perovskite are ionic compounds that can be well dissolved into polar solvents, PNCs can be fabricated through either ex situ routes in flask or in situ strategies on substrates. The in situ fabricated PNCs are adaptable to devices integration due to their scalable and low-cost manufacturing. In this regard, more and more efforts have been made in terms of the controlling synthesis, physical properties and device applications of PNC materials.After over 30 years of development, colloidal quantum dots have now become mature luminescent materials in photonic and optoelectronic operations and start to hit the market. The emerging perovskite nanocrystals are expected to promote large-scale commercialization due to their superior optical properties as well as low cost and easy fabrication. This progress report is focused on the...

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“…[13][14][15][16][17][18][19][20][21][22][23] Among these stimuli, the electric field stimulated luminescence response is a facile and promising way for the design of stimulus-responsive materials. [28][29][30][31][32] www.advopticalmat.de luminescence color change from orange to green. Up to now, some examples of electrochromic luminescent (ECL) materials have been reported.…”

Section: Introductionmentioning

confidence: 99%

Phosphorescent Ionic Iridium(III) Complexes Displaying Counterion‐Dependent Emission Colors for Flexible Electrochromic Luminescence Device

Yang

Liu

et al. 2017

Advanced Optical Materials

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Phosphorescent transition-metal complexes, typically exhibiting various chargetransfer excited states, such as triplet metal-to-ligand charge transfer ( 3 MLCT), ligand-to-ligand charge transfer ( 3 LLCT), intraligand charge transfer ( 3 ILCT), and metal-to-ligand-ligand charge transfer ( 3 MLLCT) states, [33][34][35][36][37] are ideal candidates for stimuli-responsive luminescent materials. These complexes can show highly sensitive optical properties toward surrounding microenvironment or external stimuli. In the previous work, it was reported that the emission color of a cationic iridium(III) complex that contains a NH group in the N^N ligand can be varied by changing its counterion. [32] Additionally, the emission color of this complex can also be changed by applying a voltage, and an information recording device has been successfully constructed on the basis of this interesting ECL property. Nevertheless, there are still several critical drawbacks in this system, restricting its real applications: (i) the emission range tuned by the counterions or electric field is narrow; (ii) the fabricated information recording device consists of ionic liquid BMIM + PF 6 − and silica nanoparticles, and the consequent quasi-solid film device suffers from the low thermal stability and mechanical strength. Thus, it is of great importance to develop excellent stimuli-responsive luminescent materials with a wide wavelength tuning range, and electrolytes with high stability and mechanical strength to solve the existing problems.In this present study, a series of iridium(III) complexes [(CZPY) 2 IrNH] + X − (CZPY = 9-hexyl-3-pyridylcarbazole, NH = 2,2′-dibenzimidazole, X − = PF 6 − , I − , Br − , or Cl − ) that contain two NH units in their N^N ligand (NH) have been designed and synthesized to address the abovementioned limits. It is known that the formation of hydrogen bond increases the electron cloud density on the nitrogen atom of the NH moiety and thus elevates the lowest enoccupied molecular orbital (LUMO) energy level. [38] Compared with the complexes containing only one NH moiety in N^N ligand, the formation of two hydrogen bonds might further elevate the LUMO energy level and increase the energy gap between highest occupied molecular orbital (HOMO) and LUMO, thus widening the emission wavelength tuning range. The tuning range of emission wavelength for these complexes can be extended to nearly 100 nm, and [(CZPY) 2 IrNH] + PF 6 − (Ir1) exhibited an electric field induced Stimulus-responsive luminescent materials have drawn considerable interest because they are ideal candidates for optoelectronic applications. Herein, a series of phosphorescent iridium(III) complexes [(CZPY) 2 IrNH] + X − (X − = PF 6 − , I − , Br − , Cl − ) containing two NH moieties in the N^N ligand is reported. These complexes exhibit significantly counterion-dependent emission color change from green (493 nm) to orange (590 nm) in CH 3 CN. Besides, the emission color of [(CZPY) 2 IrNH] + PF 6 − is sensitive to the external electric field. Upon a...

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Transcending the slow bimolecular recombination in lead-halide perovskites for electroluminescence

Cited by 532 publications

References 43 publications

The Dominant Energy Transport Pathway in Halide Perovskites: Photon Recycling or Carrier Diffusion?

The Dominant Energy Transport Pathway in Halide Perovskites: Photon Recycling or Carrier Diffusion?

In Situ Fabricated Perovskite Nanocrystals: A Revolution in Optical Materials

Phosphorescent Ionic Iridium(III) Complexes Displaying Counterion‐Dependent Emission Colors for Flexible Electrochromic Luminescence Device

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