Precursor stoichiometry in CH 3 NH 3 PbBr 3 . Structure-property - - PowerPoint PPT Presentation

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Aug 07, 2023 512 likes •711 views

Precursor stoichiometry in CH 3 NH 3 PbBr 3 . Structure-property relationship and LED implication Giulia Longo, Michele Sessolo and H.J.Bolink giulia.longo@uv.es Institiuto de Ciencia Molecular (ICMol) University of Valencia Organic-inorganic

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Precursor stoichiometry in CH3NH3PbBr3. Structure-property relationship and LED implication

Giulia Longo, Michele Sessolo and H.J.Bolink giulia.longo@uv.es Institiuto de Ciencia Molecular (ICMol) University of Valencia

SLIDE 2

Organic-inorganic cubic perovskites

L- Gil-Escrig, G. Longo, A. Pertegas, C. Roldan-Carmona, A. Soriano, M. Sessolo and H. J. Bolink, Chem. Commun, 2015, 51

K. Tvingstedt, O. Malinkiewicz, A. Baumann, C. Deibel, H. J. Snaith, V. Dyakonov and H. J. Bolink, Sci. Rep., 2014, 4.

5.9 eV 3.6 eV 2.3 eV 539 nm I- Br- 5.4 eV 3.7 eV 1.6 eV 770 nm CH3NH3PbI3 CH3NH3PbBr3

Corner sharing lead halide octahedra (PbX2) + Methylammonium halide (CH3NH3X) E

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Analyzed samples

Stoichiometric CH3NH3:PbBr2 = 1 Non-stoichiometric CH3NH3:PbBr2 = 3 Single step deposition technique

MABr PbBr2 Substrate

90 °C

Substrate perovskite

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Powder diffraction analysis

10 15 20 25 30 35 40 45 50

2 q (degree)

1:1 3:1

* * * * * *

Polycristalline powders precipitated from concentrated solutions Precipitating agent: chlorobenzene Dryed at 75° for 48 hours, and then annealed at 90°C for 3h. Sample 3:1 was further annealed at 115°C for 24 hours

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Solid state C13 NMR analysis

5 34 32 30 28 26 24 13C shift (ppm) 1-1 MABr 1-3

Free CH3NH3Br Bounded CH3NH3Br

freeMA/Pb-MA= 1.38 Total MA/Pb = 2.38 20% lost during thermal treatment (90°C 3 hours)

34 32 30 28 26 24 13C shift (ppm) 1-3-ann 1-3

Even after thermal treatment (115°C 24h), the same ratio between bounded and unbounded methilammonium is kept

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Device structure

3.6 6.8 2.6 5.9 4.8 Glass/ITO PEDOT:PSS:nafion Perovskite BmPhPyB

Ba/Ag

5.1 2.4 BmPhPyB Perovskite Ba/Ag

PEDOT:PSS: PFI

ITO E (eV)

H. Cho et al.,Science, 2016,350,1222-1225

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3-1 OLED device

Glass/ITO PEDOT:PSS:nafion Perovskite BmPhPyB

Ba/Ag

1 2 3 4 5 6 0.01 0.1 1 10 100 1000 Current density (A/m^2) Voltage (V) 0.001 0.01 0.1 1 10 100 Luminance (Cd/m^2)

Built-in voltage Drift

CH3NH3Br/PbBr2=3

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1-1 OLED device

1 2 3 4 5 6 1 10 100 1000 10000 Voltage (V) 0.01 0.1 1 10 100 Current density (A/m^2) Luminance (Cd/m^2)

Glass/ITO PEDOT:PSS:nafion Perovskite BmPhPyB

Ba/Ag

CH3NH3Br/PbBr2=1

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Morphological study

In Pb Br

a b c d

MA/Pb =1 MA/Pb =3

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Relationship of performances and structure

1 2 3 4 5 6 0.01 0.1 1 10 100 1000 Current density (A/m^2) Voltage (V) 0.001 0.01 0.1 1 10 100 Luminance (Cd/m^2) 1 2 3 4 5 6 1 10 100 1000 10000 Voltage (V) 0.01 0.1 1 10 100 Current density (A/m^2)

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Optical behavior

11 475 500 525 550 575 600

Electroluminescence intensity (normalized)

EL Dev1 EL Dev3 Wavelenght (nm)

537 545

300 350 400 450 500 550 600 650 0.0 0.2 0.4 0.6 0.8

1-3 1-1

Wavelenght (nm) Absorption (a.u.)

530 537

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Electroluminescence and photoluminescence

12 450 475 500 525 550 575 600

PL 1-3 PL 1-1

Photoluminescence intensity (a.u.) Wavelenght (nm)

527 Excitation wavelength: 365nm 537

475 500 525 550 575 600

Electroluminescence intensity (normalized)

EL Dev1 EL Dev3 Wavelenght (nm)

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Trap states filling

X X X

1-1 sample No photoluminescence 1-3 sample Photoluminescence at 527nm

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Trap assisted recombination

ETL Ba cathode

1-3 photoluminescence: 527 nm 1-3 electroluminescence: 537 nm

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Conclusions

Precursor stoichiometry of CH3NH3PbBr3 have a fundamental role in

the optoelectronic properties and in film formation

An excess of methylammonium affects the perovskite bandgap
An excess of methylammonium bromide favors the surface

coverage and the creation of a compact and uniform perovskite layer, suitable for optoelectronic application

The excess of MABr passivates the trapping states present on the

crystals allowing photoluminescence even at low excitation intensities

The electroluminescence in the device likely derives from trap

assisted recombination processes.

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Acknowledgments

Dr. Henk J. Bolink
Dr. Michele Sessolo
Dr. Maria Monrabal-Capilla

Lidon Gil-Escrig Laura Martinez-Sarti Mª Cristina Momblona Rincon David Forgacs Enrico Bandiello Antonio Pertegas-Ojeda Jorge Pablo Avila-Gomez Jorge Ferrando-Garcia Araceli Miquel-Sempere

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Thank you for your attention!

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