Highly Conductive Alkaline‐Earth Metal Electrodes: The Possibility of Maintaining Both Low Work Function and Surface Stability for Organic Electronics

Abstract

The realization of a highly efficient and transparent light‐emitting display isan ambitious but highly desirable goal since several obstacles need to be solved. One of the most challenging issues is the fabrication of a suitable transparent cathode on the top emitting surface. Evaporated Ca thin film is one theoretically promising candidate due to its remarkable optical transparency, conductivity, and matched work function (WF) on the electron injection side. However, until now, keeping metallic Ca working as a stand‐alone electrode is not possible because its highly reactive characteristics cause ultrathin Ca film to react with organics. In this work, atomic layer deposition ZnO is presented with the intention of protecting a vulnerable ultrathin Ca layer while preserving its low WF in the entire structure. In this research, a transparent cathode that maintains a low WF of 3.31 eV is built, enabling highly transparent (nearly 90% in the visible range) organic light‐emitting diodes with external quantum efficiencies that reach 22.7%, 19.3%, and 17.9% for green, yellow, and blue emissions, respectively, and reaching an emission balance. The luminance of the devices is about three times higher when compared with the devices without protective structures, which are even likely to fail to operate.

Vacuum‐Deposited Transparent Organic Photovoltaics for Efficiently Harvesting Selective Ultraviolet and Near‐Infrared Solar Energy

“…[ 31 ] Among these transparent anode or cathode electrodes, the electrodes with the multilayered structure, i.e., buffer layer/thin metal/buffer layer, provide efficient charge injection, high transparency, and excellent mechanical flexibility as compared to the standard transparent conductive oxides. [ 32 ] But, to achieve high AVT and PCE of a TPV, the transparent electrode should possess several particular optoelectrical properties. For example, a transparent multilayered electrode needs to offer a high transmittance value in the range of 450–650 nm and reflect only the NIR/UV light.…”

Recent Progress on Emerging Transparent Metallic Electrodes for Flexible Organic and Perovskite Photovoltaics

“…This approach was demonstrated recently in both the anode and cathode of light-emitting diodes with improved performance. [125,126] Furthermore, with the engineering of the materials and thickness of each layer, multilayered metal film structures are shown to provide a range of benefits including transmittance gain (by suppressing metal reflection and producing selective transparency), [127,128] electrode anticorrosion property, [129,130] switching failure avoidance, [131] and mechanical durability against deformation, [132][133][134] among others. To obtain a continuous metal film with minimum thickness in the multilayered sandwich structure, improving the wetting of metal clusters on the supporting layer is also crucial.…”

Review of porphyrin-based photodynamic therapy materials

“…Among these, the study of photo-responsive functional block copolymers owing to their significant physical and chemical properties is a quite interesting yet challenging research topic [96][97][98][99]. As a typical photoresponsive functional unit, porphyrin-based block copolymers have been well studied and used in applications including solar cells, catalysis, light harvesting, and biomedicines [100][101][102][103]. Similarly, a good number of studies on porphyrin-based block copolymers have been conducted especially to utilize them in PDT itself and PDT involved therapies [104,105].…”