A Study about the Effect of Perovskite Nanocrystals (CsPbBr3) Purity on the Stability of Light-Emitting Diodes Perfromance
Alexis Villanueva-Antolí a, Rafael Sanchez a, Iván Mora-Seró a
a Institute of Advanced Materials (INAM), Universitat Jaume I, Av. Sos Baynat, s/n, 12071 Castelló, Spain
Proceedings of International Conference on Emerging Light Emitting Materials (EMLEM22)
Materials for next generation LEDs and lasers:
Limasol, Cyprus, 2022 October 3rd - 5th
Organizers: Maksym Kovalenko, Maryna Bodnarchuk and Grigorios Itskos
Poster, Alexis Villanueva-Antolí, 079
Publication date: 15th July 2022

Halide perovskites (HPs) have attracted enormous interest in the area of semiconductor materials and optoelectronic devices due to their fascinating properties, such as narrow photoluminescence (PL) spectra, extremely high PL quantum yields (PLQY), tunable band gap (Eg) and tolerance to crystalline defects. All these features together with the versatility from the synthesis perspective and the high tolerance to crystalline defects, have contributed to establish HPs as excellent candidates for the fabrication of high-performance and low-cost optoelectronic devices, e.g. light-emitting diodes (LEDs) and solar cells. Beyond photovoltaics, HP-based LEDs have experienced outstanding efficiency records, with External Quantum Efficiencies (EQEs) >20%, high luminance values and excellent color purity levels. Unfortunately, the operational stabilities reached so far are well below the strict technological standards required for an eventual market approach, and the knowledge about the photo-electro-chemical mechanisms behind the device's functioning remain unclear. In this work, we have carefully synthesized HP (CsPbBr3) nanocrystals through a hot-injection procedure and thoroughly applied an optimized purification method as to ensure the excellent quality of the material, followed by the fabrication of green light-emitting devices based on the ITO/PEDOT:PSS/poly-TPD/CsPbBr3/PO-T2T/LiF/Al architecture. It is worth highlighting the maximum EQE and luminance values obtained, 20.65% and 81875 Cd·m-2, respectively, which are comparable or even superior to the state-of-the-art. Moreover, we have evaluated their operational stability under constant applied potential at different luminance levels and tried to identify the main processes involved in their loss of performance during functioning. Our advanced characterization based on frequency resolved techniques, points to the electrically-induced generation of surface and/or bulk crystalline defects in the HP NCs, as the main mechanism involved in the loss of the performance of the devices. This deleterious effect might be directly related to the ion migration, generally observed in HPs, and therefore, we believe that the enhancement of the stability levels must be tackled from the perspective of inhibiting (or minimizing) the ionic mobility.

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