Organometal halide perovskite as hole injection enhancer in organic light-emitting diode

Tetraalkyl-substituted zinc phthalocyanines used as anode buffer layers for organic light-emitting diodes*

“…[4] Device efficiency and device lifetime, which are the two main concerns for practical use, are directly related to the energy consumption and long-term stability/durability and are largely governed by the charge balance in OLEDs. [5][6][7][8] Therefore, to obtain an efficient OLED, it is essential to optimize the charge carrier injection, transport, and recombination processes in the device. [5,6,9] Indium tin oxide (ITO) is the preferred anode material for use in electroluminescent devices because of its high conductivity and high transparency in the visible spectral regime.…”

“…[10][11][12][13] The metal oxides such as WO 3 , [14] V 2 O 5 , [15] MoO 3 , [3,13,[16][17][18] ReO 3 , [19] and NiO x [20] are important HIL materials and have been used widely to enhance the hole injection because they offer appropriate energy levels, good thermal stability, and excellent charge carrier mobility. [8] However, these inorganic HILs are usually prepared by annealing a precursor layer at relatively high temperatures, which thus limits the application of these materials in flexible electronic products. [8] Conducting polymers represent another class of HIL/HTL materials.…”

“…[8] However, these inorganic HILs are usually prepared by annealing a precursor layer at relatively high temperatures, which thus limits the application of these materials in flexible electronic products. [8] Conducting polymers represent another class of HIL/HTL materials. Their unique optical and electrical properties have allowed them to demonstrate promising potentials for use in flexible optoelectronic devices.…”

“…Their unique optical and electrical properties have allowed them to demonstrate promising potentials for use in flexible optoelectronic devices. [8] Among these materials, poly- (3, 4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) is one of the most popular HIL/HTL materials because of its appropriate energy levels and ability to form smooth films on ITO substrates. [21,22] Unfortunately, challenges including ITO etching, indium diffusion, water residue, exciton quenching, and weak adhesion still exist.…”

“…[2,9,23,24] In addition, water residue induced by aqueous PEDOT: PSS dispersion can introduce damage to the devices that typically leads to poor long-term durability. [8,9] Since the first demonstration of the use of copper phthalocyanine (CuPc) to modify the ITO anode of an OLED by Tang and VanSlyke in 1996, [5] the use of metal phthalocyanines (MPcs) as anode buffer layers has been subject to intensive investigation with the aim of achieving higher OLED efficiencies and stabilities. [5,9,10,[25][26][27][28][29][30] In most cases, these MPc layers are fabricated via the vacuum sublimation method because of the poor solubility of typical MPcs in organic solvents.…”