Investigating Ambient Air Processed Inkjet-Printed Electron Blocking Layer (EBL) and Nanocrystalline CsPbBr3 Emission Layer for Perovskite Based LEDs
Gayathri Mathiazhagan a b, Sergio González-Torres a b, Jesus Sanchez-Diaz c, Giovanni Vescio a b, Joan Cano a b, Andrés Gualdrón-Reyes c, Marek Oszajca d, Alina Hauser d, Sergi Hernández a b, Ivan Mora-Seró c, Albert Cirera a b, Blas Garrido a b
a MIND, Department of Electronics and Biomedical Engineering, Universitat de Barcelona, Martí i Franquès 1, E-08028, Barcelona, Spain
b Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Av. Joan XXIII S/N, E-08028, Barcelona, Spain
c Institute of Advanced Materials (INAM), Universitat Jaume I (UJI), Avenida de Vicent Sos Baynat, s/n, 12071 Castelló de la Plana, Spain
d Avantama AG, Laubisruetistrasse 50, Staefa 8712, Switzerland
Proceedings of Sustainable Metal-halide perovskites for photovoltaics, optoelectronics and photonics (Sus-MHP)
València, Spain, 2022 December 12th - 13th
Organizers: Teresa S. Ripolles and Hui-Seon Kim
Oral, Gayathri Mathiazhagan, presentation 030
Publication date: 15th November 2022

Lead halide perovskites (LHPs) have shown outstanding optical emissive properties and can be used in displays, either as color conversion layers (CCLs) or self-emissive light emitting diodes (LEDs). Well‑established technologies (OLEDs, MicroLEDs) are either prone to degradation or require expensive materials and technology. Inorganic LHPs are demonstrating to be more stable than their organic counterparts wherein higher efficiencies are displayed for spin-coated devices. In this work, we propose inkjet printing as an industrial-friendly technique to deposit LHPs as a method for producing low-cost, large-area CCL and LEDs. We have developed inks from colloidal nanocrystals of CsPbBr3. Subsequently, inkjet printing parameters have been optimized to allow thin layer deposition with a strong emission. CsPbBr3 printed layers emit at 524 nm with a narrow emission of an FWHM about 15 nm [1].

Exploiting these results, we propose the fabrication of green-emitting LEDs based on CsPbBr3 in ambient conditions by inkjet printing. In this work, several inverse structural (p-i-n) configurations are tested in order to investigate the influence and role of the selected transport layers. We emphasize the significant contribution of inkjet-printed (IJP) NiO onto the commonly used hole injection material poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) to increase device performance and stability. Even though with challenging crystallization dynamics for IJP technology, our devices with IJP NiO show excellent performances similar to devices with widely used spin-coated organic EBL layer (poly [bis (4-phenyl) (4-butylphenyl) amine i.e., Poly-TPD). Thus, inkjet-printed CsPbBr3 LEDs incorporating NiO as EBL yields increased luminance (10000 cd m−2) with a turn‑on voltage of ~ 5 V and an external quantum efficiency of ~ 3%. Furthermore, the shelf-life of these devices will also be analyzed. Thereupon, this work constructs the initial steps towards stable fully inkjet‑printable perovskite light-emitting devices for a wide variety of low-cost and customizable applications.

The authors wish to the financial support from the European Commission via FET Open Grant (862656 – DROP-IT), and MINECO (Spain) for grant PID2019-105658RB-I00 (PRITES project). S.G.T acknowledges the program “Ajuts de personal investigador predoctoral en formació (APIF)" from the Universitat de Barcelona for economical support.

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