Organic semiconductors with very small optical energy gaps have attracted a lot of attention for near-infrared-active optoelectronic applications. Herein, we present a series of donor-acceptor-donor (D−A−D) organic semiconductors consisting of a highly electron-deficient naphtho[1,2-b:5,6-b′]dithiophene-2,7-dione quinoidal acceptor and oligothiophene donors that show very small optical energy gaps of down to 0.72 eV in the solid state. Investigation of the physicochemical properties of the D−A−D molecules as well as theoretical calculations of their electronic structures revealed an efficient intramolecular interaction between the quinoidal acceptor and the aromatic oligothiophene donors in the D−A−D molecules; this significantly enhances the backbone resonance and thus reduces the bond length alternation along the π-conjugated backbones. Despite the very small optical energy gaps, the D−A−D molecules have low-lying frontier orbital energy levels that give rise to air-stable ambipolar carrier transport properties with hole and electron mobilities of up to 0.026 and 0.043 cm2 V−1 s−1, respectively, in field-effect transistors. 相似文献
A series of novel red phosphorescent polymers is successfully developed through Suzuki cross‐coupling among ambipolar units, functionalized IrIII phosphorescent blocks, and fluorene‐based silane moieties. The photophysical and electrochemical investigations indicate not only highly efficient energy‐transfer from the organic segments to the phosphorescent units in the polymer backbone but also the ambipolar character of the copolymers. Benefiting from all these merits, the phosphorescent polymers can furnish organic light‐emitting diodes (OLEDs) with exceptional high electroluminescent (EL) efficiencies with a current efficiency (ηL) of 8.31 cd A−1, external quantum efficiency (ηext) of 16.07%, and power efficiency (ηP) of 2.95 lm W−1, representing the state‐of‐the‐art electroluminescent performances ever achieved by red phosphorescent polymers. This work here might represent a new pathway to design and synthesize highly efficient phosphorescent polymers.
The field of organic electronics has been developed vastly in the past two decades, and the performance and lifetime of these devices are critically dependent on the materials development, device design, deposition processes, and modeling, among which the active materials of organic semiconductor play a crucial role. The unique properties of organic semiconductor are largely based on the versatility to synthesize multifunctional organic conjugated materials by judicious molecular design. To effectively adjust the optoelectronic properties, especially energy levels, of organic semiconductor, the scientists have presented a synthesis methodology of organic ambipolar conjugated molecules, in which typical p‐dope type and n‐dope type segments are incorporated into one molecule. The present review summarizes the progress on organic ambipolar conjugated molecules for electronics in the past few years. Some issues to be addressed are also highlighted and discussed.
Using the first-principles band-structure method and a special quasirandom structure(SQS) approach,we have systematically calculated the alloy bowing coefficients and the nature band offsets of SnxZn1-x Te alloys.We show that the bowing coefficients and band gaps of these alloys are sensitively composition dependent.Due to wave functions full overlapping and delocalization of the Sn outermost p orbits and Zn s orbits,the coupling between these states is very strong,resulting in a significant downshift of conduction band edge with the increase of the Sn concentration x,While the valence band edge keeps almost unchanged compared with that of the binary ZnTe,thus improving the possibility for ambipolar-doping. 相似文献
Fabrication of ambipolar organic field-effect transistors (OFETs) is
essential for the achievement of an organic complementary logic
circuit. Ambipolar transports in OFETs with heterojunction
structures are realized. We select pentacene as a P-type material and
N,N'-bis(4-trifluoromethylben-zyl)perylene-3,4,9,10-tetracarboxylic
diimide (PTCDI-TFB) as a n-type material in the active layer of the
OFETs. The field-effect transistor shows highly air-stable ambipolar
characteristics with a field-effect hole mobility of
0.18~cm2/(V.s) and field-effect electron mobility of
0.031~cm2/(V.s). Furthermore the mobility only slightly
decreases after being exposed to air and remains stable even for
exposure to air for more than 60 days. The high electron affinity of
PTCDI-TFB and the octadecyltrichlorosilane (OTS) self-assembly
monolayer between the SiO2 gate dielectric and the organic
active layer result in the observed air-stable characteristics of
OFETs with high mobility. The results demonstrate that using the OTS
as a modified gate insulator layer and using high electron affinity
semiconductor materials are two effective methods to fabricate OFETs
with air-stable characteristics and high mobility. 相似文献