Optoelectronic Functional Materials Research Articles

From Molecules to Materials: Molecular and Crystal Engineering Design of Organic Optoelectronic Functional Materials for High Carrier Mobility

The reorganization energy and the charge transfer integral between the initial and final states are two key parameters of charge transport. In this study, we find that the internal reorganization energies of molecules can be reduced effectively by cyanation on the tetracene molecule, which is helpful to improve the carrier mobilities of investigated molecules. On the basis of the polymorph predictor, the appreciated crystal structures of 5-cyanotetracene (1CT), 5,11-dicyanotetracene (2CT), and 5,6,11,12-tetracyanotetracene (4CT) with π–π stacking favorable to enhance the charge transfer integral were obtained. Benefiting from a low internal reorganization energy and dense packing structure, high hole motilities (6.0 and 6.2 cm2 V–1 s–1 for 1CT-9 and 4CT-2, respectively) were achieved. Both 1CT-9 and 4CT-2 are promising candidates for high carrier mobility organic optoelectronic functional materials. The process that constructs crystal structures from single molecules provides a rational way for the search of high-performance organic photovoltaic materials.

Theoretical studies of the structural, electronic and optical properties of carbazole‐based compounds

Carbazole derivatives have drawn increasing attention recently in organic electronic device applications because of their particular optoelectronic properties. An in‐depth theoretical investigation was elaborated in this paper to reveal the molecular structures, optoelectronic properties, and the structure‐property relationships of different carbazole‐linked functional groups. The geometric and electronic structures in ground and the mobility for the hole and electron are both calculated by density functional theory method. The excited‐state geometries of these compounds were obtained through Single‐excitation Configuration Interaction method, and time‐dependent density functional theory calculation results described the absorption and emission spectra properties, respectively. Some conclusions are as follows: (1) enlarging the π‐conjugated area, the corresponding spectra red shifted markedly; (2) by introducing the electron‐donor such as carbazole, the spectra blue shifted slightly; (3) compared with compound 1, the spectra for these compounds are hardly influenced by introducing an electron‐acceptor or heterocyclic substitution. On all accounts, these compounds are interesting optoelectronic functional materials. On the basis of their structural modifiability, the arylamine derivatives substituted carbazole compounds have great potential in the applications of organic light‐emitting diodes, organic solar cells, and sensors. Copyright © 2011 John Wiley & Sons, Ltd.

Theoretical Studies of the Structural, Electronic, and Optical Properties of Phosphafluorenes

Phosphafluorenes have drawn increasing attention recently in the applications of organic electronic devices due to their particular optoelectronic properties. To reveal their molecular structures, optoelectronic properties, and structure-property relationships of the newly emerged functional materials, an in-depth theoretical investigation was elaborated via quantum chemical calculations. The optimized geometric and electronic structures in both ground and exited states, the mobility of the hole and electron, the absorption and emission spectra, and the singlet exciton generation fraction of these novel phosphors-containing materials have been studied by density functional theory (DFT), single excitation configuration interaction (CIS), time-dependent density functional theory (TDDFT) methods, and the polarizable continuum model (PCM). The results show that the highest occupied molecular orbitals (HOMOs), the lowest unoccupied molecular orbitals (LUMOs), triplet energies ((3)E(g)), energy gaps (E(g)), as well as some other electronic properties including ionization potentials (IPs), electron affinities (EAs), reorganization energies (lambda), the singlet exciton generation fraction, radiative lifetime, and absorption and emission spectra can be easily tuned by chemical modifications of the phosphorus atom via methyl, phenyl, oxygen, sulfur, or selenium substitution, indicating that the phosphafluorenes are interesting optoelectronic functional materials, which have great potential in the applications of OLEDs, organic solar cells, organic storage, and sensors.

Fabrication of Rutile TiO2−Sn/Anatase TiO2−N Heterostructure and Its Application in Visible-Light Photocatalysis

A new type of composite film (heterostructure) with optoelectronic properties have been prepared by coupling Sn-doped rutile TiO2 (R-TiO2−Sn) and N-doped anatase TiO2 (A-TiO2−N) with use of a sol−gel method. Under visible and UV light irradiation, it exhibits a higher photocatalytic activity than both R-TiO2−Sn and A-TiO2−N films due to the formation of a heterojunction at the interface, as well as the increase of total amount of photogenerated charge carriers and introduction of doping states. If R-TiO2−Sn is the outmost layer, moreover, the composite film shows a much higher photodegradation capability of HCHO than that when A-TiO2−N is the outmost layer. Our results offer a paradigm for developing optoelectronic functional materials that can be used in many fields, such as solar cells, photocatalysis, and photosynthesis.