Abstract:Hydrogen is the ideal fuel for the future because it is clean, energy efficient, and abundant in nature. While various technologies can be used to generate hydrogen, only some of them can be considered environmentally friendly. Recently, solar hydrogen generated via photocatalytic water splitting has attracted tremendous attention and has been extensively studied because of its great potential for low-cost and clean hydrogen production. This paper gives a comprehensive review of the development of photocatalytic water splitting for generating hydrogen, particularly under visible-light irradiation. The topics covered include an introduction of hydrogen production technologies, a review of photocatalytic water splitting over titania and non-titania based photocatalysts, a discussion of the types of photocatalytic water-splitting approaches, and a conclusion for the current challenges and future prospects of photocatalytic water splitting. Based on the literatures reported here, the development of highly stable visible-light-active photocatalytic materials, and the design of efficient, low-cost photoreactor systems are the key for the advancement of solar-hydrogen production via photocatalytic water splitting in the future.

In recent years, there has been considerable interest in developing blue organic light-emitting devices (OLEDs) with high efficiency, deep-blue color, and long operational lifetime. The deep-blue color is defined arbitrarily as having blue electroluminescent (EL) emission with a Commission Internationale de l'Eclairage y coordinate value (CIE y ) of < 0.15. Such emitters can effectively reduce the power consumption of a full-color OLED and can also be utilized to generate light of other colors by energy cascade to a suitable emissive dopant.It is well known that a guest-host doped emitter system can significantly improve device performance in terms of EL efficiency and emissive color, as well as operational lifetime.[1] Although many blue host materials have been reported, such as anthracene, [2] di(styryl)arylene, [3] tetra(phenyl)pyrene, [4] terfluorenes, [5] and tetra(phenyl)silyl derivatives, [6] blue-doped emitter systems having all the attributes of high EL efficiency, long operational lifetime, and deep-blue color, are rare. [7] This is because designing a fluorescent, deep-blue dopant capable of forming an amorphous glassy state upon thermal evaporation with a much shortened p-conjugation length is a rather daunting task. In addition, finding a deep-blue dopant with a small Stokes shift is essential for efficient Förster energy transfer from the host to dopant molecules, since the energy transfer efficiency is highly dependent on the spectral overlap between the emission of the host and the absorption of the dopant.Recently, we have successfully demonstrated an anthracene-based blue host material, 2-methyl-9,10-di(2-naphthyl)-anthracene (MADN), which possesses a wide energy bandgap of 3.0 eV and can also form a stable thin-film morphology upon thermal evaporation. When doped with a di(styryl)-amine-based blue dopant, p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph), it achieved a very high EL efficiency of 9.7 cd A -1 , with a greenish-blue color of CIE x,y (0.16, 0.32) and a long operational lifetime of 46 000 h at a normalized initial brightness of 100 cd m -2 .[8] However, the color saturation of the blue-doped emitter system (DSA-Ph@MADN) is far from adequate for application in full-color OLED displays. On the other hand, the symmetrical di(styryl)amine-based organic molecule is well known to possess a high fluorescent quantum yield, [9] and its emission wavelength (k max = 450-480 nm) is dependent on the p-conjugation length, which encompasses the two strongly donating arylamine moieties. However, the molecular engineering of symmetrical di(styryl)amine-based fluorescent dyes to cause hypsochromic shift has its limitations as both donors are already present as part of the styryl p-conjugation.[10]In this paper, we report a series of novel, deep-blue dopants based on unsymmetrical mono(styryl)amine derivatives, which provide us with a basic structure for color tuning within the 430-450 nm spectral region. We show that when doped in the MADN host as an OLED, some of these deep-blue dopants exhibit a...

We have developed a highly efficient and stable blue organic electroluminescent (EL) device based on a blue fluorescent styrylamine dopant, p-bis(p-N,N-diphenyl-aminostyryl)benzene, in a morphologically stable high band-gap host material, 2-methyl-9,10-di(2-naphthyl)anthracene, which achieved an EL efficiency of 9.7cd∕A and 5.5lm∕W at 20mA∕cm2 and 5.7 V, with Commission Internationale d’Eclairage coordinates of (x=0.16,y=0.32). The blue-doped device achieved a half-decay lifetime (t1∕2) of 46 000 h at an initial brightness of 100cd∕m2.