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 cubic perovskites Corner sharing lead halide octahedra ( PbX 2 ) + Methylammonium halide ( CH 3 NH 3 X ) E CH 3 NH 3 Pb Br 3 CH 3 NH 3 Pb I 3 3.6 eV 3.7 eV 2.3 eV I - Br - 1.6 eV 539 nm 770 nm 5.4 eV 5.9 eV 2 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 .
Analyzed samples Stoichiometric Non-stoichiometric CH 3 NH 3 :PbBr 2 = 1 CH 3 NH 3 :PbBr 2 = 3 Single step deposition technique perovskite MABr PbBr 2 Substrate Substrate 90 ° C 3
Powder diffraction analysis Polycristalline powders 1:1 precipitated from 3:1 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 10 15 20 25 30 35 40 45 50 24 hours 2 q (degree) 4
Solid state C 13 NMR analysis 1-3 1-1 freeMA/Pb-MA= 1.38 1-3 1-3-ann MABr Even after thermal treatment (115 ° C 24h), the same ratio Total MA/Pb = 2.38 between bounded and unbounded methilammonium is 20% lost during thermal kept treatment (90 ° C 3 hours) 34 32 30 28 26 24 34 32 30 28 26 24 13C shift (ppm) 13C shift (ppm) Bounded CH 3 NH 3 Br Free CH 3 NH 3 Br 5
Device structure Ba/Ag E (eV) 2.6 2.4 3.6 Ba/Ag BmPhPyB Perovskite BmPhPyB PEDOT:PSS: Perovskite ITO PFI PEDOT:PSS:nafion 4.8 5.1 Glass/ITO 5.9 6.8 6 H. Cho et al. , Science , 2016,350,1222-1225
3-1 OLED device Ba/Ag BmPhPyB Perovskite 100 1000 Drift PEDOT:PSS:nafion 100 10 Glass/ITO Luminance (Cd/m^2) Current density (A/m^2) 10 1 1 0.1 CH 3 NH 3 Br/PbBr 2 =3 0.1 0.01 0.01 0.001 0 1 2 3 4 5 6 Voltage (V) Built-in voltage 7
1-1 OLED device Ba/Ag BmPhPyB Perovskite 10000 100 PEDOT:PSS:nafion Glass/ITO Luminance (Cd/m^2) 1000 Current density (A/m^2) 10 1 100 CH 3 NH 3 Br/PbBr 2 =1 0.1 10 0.01 1 0 1 2 3 4 5 6 Voltage (V) 8
Morphological study a b MA/Pb =1 In Pb Br c d MA/Pb =3 9
Relationship of performances and structure 10000 Current density (A/m^2) 100 1000 10 1 100 0.1 10 0.01 1 0 1 2 3 4 5 6 Voltage (V) 1000 100 Current density (A/m^2) Luminance (Cd/m^2) 100 10 10 1 1 0.1 0.1 0.01 0.01 0.001 10 0 1 2 3 4 5 6 Voltage (V)
Optical behavior Electroluminescence intensity (normalized) EL Dev1 1-3 EL Dev3 1-1 0.8 0.6 Absorption (a.u.) 0.4 530 537 0.2 537 545 0.0 475 500 525 550 575 600 300 350 400 450 500 550 600 650 Wavelenght (nm) Wavelenght (nm) 11
Electroluminescence and photoluminescence Excitation wavelength: 365nm Electroluminescence intensity (normalized) Photoluminescence intensity (a.u.) 537 EL Dev1 527 PL 1-1 EL Dev3 PL 1-3 475 500 525 550 575 600 450 475 500 525 550 575 600 Wavelenght (nm) Wavelenght (nm) 12
Trap states filling X X X 1-1 sample 1-3 sample No photoluminescence Photoluminescence at 527nm 13
Trap assisted recombination Ba cathode ETL 1-3 photoluminescence: 527 nm 1-3 electroluminescence: 537 nm 14
Conclusions • Precursor stoichiometry of CH 3 NH 3 PbBr 3 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. 15
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 16
Thank you for your attention! 17
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
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