Bright Single-Layer Perovskite Host–Ionic Guest Light-Emitting Electrochemical Cells

Mishra, Aditya; DiLuzio, Stephen; Alahbakhshi, Masoud; Adams, Austen C.; Bowler, Melanie H.; Moon, Jiyoung; Gu, Qing; Zakhidov, Anvar A.; Bernhard, Stefan; Slinker, Jason D.

doi:10.1021/acs.chemmater.0c03934

Cited by 18 publications

(11 citation statements)

References 63 publications

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“…We investigated CsPbBr 3− x Cl x PeLECs by voltage sweeping and constant current, as shown in Figure . We present the 10th voltage sweep data, as they exhibited 20% to 50% better performance than data from the first sweep, likely from greater EDL formation due to slow ion relaxation [ 7a,11 ] and reduced trap density from electrical stress. [ 12 ] (See Tables S3 and S4, Supporting Information, for the comparison.)…”

Section: Resultsmentioning

confidence: 99%

Pure Blue Electroluminescence by Differentiated Ion Motion in a Single Layer Perovskite Device

Mishra

Alahbakhshi

Haroldson

et al. 2021

Adv Funct Materials

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Blue electroluminescence is highly desired for emerging light‐emitting devices for display applications and optoelectronics in general. However, saturated, efficient, and stable blue emission has been challenging to achieve, particularly in mixed‐halide perovskites, where intrinsic ion motion and halide segregation compromises spectral purity. Here, CsPbBr3−xClx perovskites, polyelectrolytes, and a salt additive are leveraged to demonstrate pure blue emission from single‐layer light‐emitting electrochemical cells (LECs). The electrolytes transport the ions from salt additives, enhancing charge injection and stabilizing the inherent perovskite emissive lattice for highly pure and sustained blue emission. Substituting Cl into CsPbBr3 tunes the perovskite luminescence from green through blue. Sky blue and saturated blue devices produce International Commission on Illumination coordinates of (0.105, 0.129) and (0.136, 0.068), respectively, with the latter meeting the US National Television Committee standard for the blue primary. Likewise, maximum luminances of 2900 and 1000 cd m−2, external quantum efficiencies (EQEs) of 4.3% and 3.9%, and luminance half‐lives of 5.7 and 4.9 h are obtained for sky blue and saturated blue devices, respectively. Polymer and LiPF6 inclusion increases photoluminescence efficiency, suppresses halide segregation, induces thin‐film smoothness and uniformity, and reduces crystallite size. Overall, these devices show superior performance among blue perovskite light‐emitting diodes (PeLEDs) and general LECs.

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Section: Resultsmentioning

confidence: 99%

Pure Blue Electroluminescence by Differentiated Ion Motion in a Single Layer Perovskite Device

Mishra

Alahbakhshi

Haroldson

et al. 2021

Adv Funct Materials

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“…In the same context, we note with interest that it is common to include a relatively thin (typically ≈20–40 nm) spin‐coated layer of PEDOT:PSS in between the ITO anode and the active material in conventional closed‐electrode‐LECs. [ 67–69 ] The motivation for the inclusion of this “intermediate layer” in LEC devices has, to our knowledge, not been systematically studied, but the herein presented results imply that a similar transfer of anions into the PEDOT:PSS layer could be expected, albeit at lower relative magnitude (since the PEDOT:PSS layer is thinner than the active material). This in turn suggests that the PEDOT:PSS layer becomes additionally p‐type doped, and that the p‐n junction as a consequence is shifted away from the reflective Al cathode towards the anode.…”

Section: Resultsmentioning

confidence: 90%

Evidence and Effects of Ion Transfer at Active‐Material/Electrode Interfaces in Solution‐Fabricated Light‐Emitting Electrochemical Cells

Auroux

Sandström

Larsen

et al. 2021

Adv Elect Materials

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The light‐emitting electrochemical cell (LEC) allows for energy‐ and cost‐efficient printing and coating fabrication of its entire device structure, including both electrodes and the single‐layer active material. This attractive fabrication opportunity is enabled by the electrochemical action of mobile ions in the active material. However, a related and up to now overlooked issue is that such solution‐fabricated LECs commonly comprise electrode/active‐material interfaces that are open for transfer of the mobile ions, and it is herein demonstrated that a majority of the mobile anions in a common spray‐coated active material can transfer into a spray‐coated poly(3,4‐ethylenedioxythiophene):poly(styrene‐sulfonate) (PEDOT:PSS) positive electrode during LEC operation. Since it is well established that the mobile ion concentration in the active material has a profound influence on the LEC performance, this significant ion transfer is an important factor that should be considered in the design of low‐cost LEC devices that deliver high performance.

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“…This is experimentally observed, as complexes with larger molar absorptivities (ε o ) approach an independence of the initial rate of Sn(0) deposition on [Ir(III)] at lower concentrations of photocatalyst, exemplified by a plot of α against ε o of all 22 Ir(III) photocatalysts (Figure A). Increasing absorptivity can be achieved by either lowering the HOMO–LUMO gap through synthetic tuning or using highly conjugated C^N or N^N ligands. , For example, despite the opposite electronics of the C^N ligand of Ir5 (electron rich, with a tert -butyl substituted phenyl ring, Figure ) and Ir8 (electron poor, with a −CF 3 substituted phenyl ring, Figure ), their respective molar absorptivities at 440 nm are very similar (Table ), attributed to the highly conjugated bathophenanthroline ancillary ligand. This is a particularly useful characteristic, as it allows photocatalysts to possess both potent excited state reduction potentials and large molar absorptivity in the visible region.…”

Section: Results and Discussionmentioning

confidence: 99%

Understanding Ir(III) Photocatalyst Structure–Activity Relationships: A Highly Parallelized Study of Light-Driven Metal Reduction Processes

et al. 2022

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High-throughput synthesis and screening methods were used to measure the photochemical activity of 1440 distinct heteroleptic [Ir(C^N) 2 (N^N)] + complexes for the photoreduction of Sn(II) and Zn(II) cations to their corresponding neutral metals. Kinetic data collection was carried out using home-built photoreactors and measured initial rates, obtained through an automated fitting algorithm, spanned between 0−120 μM/s for Sn(0) deposition and 0−90 μM/s for Zn(0) deposition. Photochemical reactivity was compared to photophysical properties previously measured such as deaerated excited state lifetime and emission spectral data for these same complexes; however, no clear correlations among these features were observed. A formal photochemical rate law was then developed to help elucidate the observed reactivity. Initial rates were found to be directly correlated to the product of incident photon flux with three reaction elementary efficiencies: (1) the fraction of light absorbed by the photocatalyst, (2) the fraction of excited state species that are quenched by the electron donor, and (3) the cage escape efficiency. The most active catalysts exhibit high efficiencies for all three steps, and catalyst engineering requirements to maximize these elementary efficiencies were postulated. The kinetic treatment provided the mechanistic information needed to decipher the observed structure/function trends in the high-throughput work.

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Bright Single-Layer Perovskite Host–Ionic Guest Light-Emitting Electrochemical Cells

Cited by 18 publications

References 63 publications

Pure Blue Electroluminescence by Differentiated Ion Motion in a Single Layer Perovskite Device

Pure Blue Electroluminescence by Differentiated Ion Motion in a Single Layer Perovskite Device

Evidence and Effects of Ion Transfer at Active‐Material/Electrode Interfaces in Solution‐Fabricated Light‐Emitting Electrochemical Cells

Understanding Ir(III) Photocatalyst Structure–Activity Relationships: A Highly Parallelized Study of Light-Driven Metal Reduction Processes

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