Bright Visible-Infrared Light Emitting Diodes Based on Hybrid Halide Perovskite with Spiro-OMeTAD as a Hole-Injecting Layer Oscar A. Jaramillo-Quintero, †,‡ Rafael S. Sanchez, † Marina Rincon, ‡ and Ivan Mora-Sero* ,† † Photovoltaic and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló , Spain ‡ Instituto de Energías Renovables, Universidad Nacional Autó noma de Me ́ xico, Apartado Postal 34, Temixco, Morelos 62580, Me ́ xico * S Supporting Information ABSTRACT: Hybrid halide perovskites that are currently intensively studied for photovoltaic applications, also present outstanding properties for light emission. Here, we report on the preparation of bright solid state light emitting diodes (LEDs) based on a solution-processed hybrid lead halide perovskite (Pe). In particular, we have utilized the perovskite generally described with the formula CH 3 NH 3 PbI 3‑x Cl x and exploited a configuration without electron or hole blocking layer in addition to the injecting layers. Compact TiO 2 and Spiro-OMeTAD were used as electron and hole injecting layers, respectively. We have demonstrated a bright combined visible-infrared radiance of 7.1 W· sr -1 ·m -2 at a current density of 232 mA·cm -2 , and a maximum external quantum efficiency (EQE) of 0.48%. The devices prepared surpass the EQE values achieved in previous reports, considering devices with just an injecting layer without any additional blocking layer. Significantly, the maximum EQE value of our devices is obtained at applied voltages as low as 2 V, with a turn-on voltage as low as the Pe band gap (V turn‑on = 1.45 ± 0.06 V). This outstanding performance, despite the simplicity of the approach, highlights the enormous potentiality of Pe-LEDs. In addition, we present a stability study of unsealed Pe-LEDs, which demonstrates a dramatic influence of the measurement atmosphere on the performance of the devices. The decrease of the electroluminescence (EL) under continuous operation can be attributed to an increase of the non- radiative recombination pathways, rather than a degradation of the perovskite material itself. S olid state light emitting diodes (LEDs) have attracted much attention over the last decades, mainly due to the need of producing more energy efficient devices by means of low-cost procedures and materials. However, these devices are generally prepared from crystalline semiconductors, which demand high temperature, high vacuum, and time-consuming methodologies, thus increasing the final cost of the product and being unsuitable, for instance, for large-area displays. 1,2 Therefore, great efforts are being devoted toward the search of new materials that must possess excellent electro-optical properties, while involving simple deposition procedures and/or mild crystal growth conditions, in order to reduce the production cost. Hybrid halide perovskite (Pe) match excellently with these material requirements and their derivatives have emerged as a very promising wide family of materials that can be exploited for a broad range of optoelectronic applications; including high performance photovoltaics, 3-7 photodetectors, 8 amplifier active devices, 9-12 and light emitting diodes. 13-17 The huge range of application of the perovskite materials rely on the unprecedented properties observed from their physical characterization. More specifically, perovskite structures have shown unique properties, such as high light absorption coefficient and room temperature photoluminescence on film, 18,19 tunable light absorption and emission, 14,20-22 long- range electron-hole diffusion lengths, 23-25 ferroelectricity, 26,27 among others. Very recent works have reported on the strong photoluminescent properties of lead halide perovskites, 28,29 with photoluminescence quantum yields (PLQY) as high as 70% at high photon fluxes. 29 Therefore, these materials are envisaged to be ideal candidates for the development of high efficiency and cost-effective solution-processed light emitting diodes. In fact, hybrid halide perovskites were studied for this purpose at the end of the past century, and the EL was indeed demonstrated; however, the scarce works that could found in the literature involved complex nonsolution deposition procedures. 30,31 The intensive work dedicated to the study of these materials, mainly due to their enormous potentiality for photovoltaic applications, and the progress made on the development of Pe-based devices in recent years, have successfully awaken the interest for using them as light emitters. Consequently, very recent works focused on the application of Pe for LEDs devices have emerged. 13-17 Here, we report on the preparation of visible-infrared bright light emitting diodes based on CH 3 NH 3 I 3-x Cl x , which show high EQE values at a low applied voltage and a very low turn- on voltage. To do so, we have exploited a device configuration that has been successfully employed for the preparation of perovskite solar cells (PSCs). Very recently, Bolink and co- workers have shown that a PSCs prepared by evaporation with organic selecting contacts can exhibit also a good electro- luminescence. 13 In our approach, a fully solution processed device, with the exception of the evaporated Au contacts, has Received: April 8, 2015 Accepted: May 1, 2015 Letter pubs.acs.org/JPCL © XXXX American Chemical Society 1883 DOI: 10.1021/acs.jpclett.5b00732 J. Phys. Chem. Lett. 2015, 6, 1883-1890