Highly Soluble CsPbBr<sub>3</sub> Perovskite Quantum Dots for Solution-Processed Light-Emission Devices
Yongfeng Liu, Shi Tang, Junpeng Fan, Eduardo Gracia‐Espino, Jinpeng Yang, Xianjie Liu, Satoshi Kera, Mats Fahlman, Christian Larsen, Thomas Wågberg, Ludvig Edman, Jia Wang
Abstract
We report on the synthesis of CsPbBr3 perovskite quantum dots (PeQDs) with a high solubility of 75 g/L in toluene and a good film-forming property, as enabled by a dense layer of didodecyldimethylammonium bromide and octanoic acid surface ligands. The crystalline and monodisperse PeQDs feature a cubic-like shape, with an edge length of 10.1 nm, and a high photoluminescence quantum yield of greater than 90% in toluene solution and 36% as a thin film. We find that the PeQDs are n-type doped following the synthesis but also that they can be p-type and additionally n-type doped by in situ electrochemistry. These combined properties render the PeQDs interesting for the emitter in solution-processed light-emitting electrochemical cells (LECs), and we report a PeQD-LEC with air-stabile electrodes that emits with a narrow emission spectrum (lambda(peak) = 514 nm, full width at half-maximum = 24 nm) and a luminance of 250 cd/m(2) at 4 V and a luminance of 1090 cd/m(2) at 6.8 V. To reach this performance, it was critical to include a thin solution-processed layer comprising p-type poly(vinyl carbazole) and a tetrahexylammonium tetrafluoroborate ionic liquid between the PeQD emission layer and the anode in order to compensate for the as-synthesized n-type doping of the PeQDs.