Gate-planarized thin film transistor substrates and related methods of fabrication

Thin film transistor substrates with conductor components in conjunction therewith, and related methods of fabrication

Very low bias stress in n-type organic single crystal transistors

Bias stress effects in n-channel organic field-effect transistors (OFETs) are investigated using PDIF-CN2 single-crystal devices with Cytop gate dielectric, both under vacuum and in ambient. We find that the amount of bias stress is very small as compared to all (p-channel) OFETs reported in the literature. Stressing the PDIF-CN2 devices by applying 80 V to the gate for up to a week results in a decrease of the source drain current of only ~1% under vacuum and ~10% in air. This remarkable stability of the devices leads to characteristic time constants, extracted by fitting the data with a stretched exponential - that are \tau ~ 2\cdot10^9 s in air and \tau ~ 5\cdot10^9 s in vacuum - approximately two orders of magnitude larger than the best values reported previously for p-channel OFETs.Comment: Submitted to Applied Physics Letters; 14 pages, 3 figure

Single-Crystal Organic Charge-Transfer Interfaces probed using Schottky-Gated Heterostructures

Organic semiconductors based on small conjugated molecules generally behave as insulators when undoped, but the hetero-interfaces of two such materials can show electrical conductivity as large as in a metal. Although charge transfer is commonly invoked to explain the phenomenon, the details of the process and the nature of the interfacial charge carriers remain largely unexplored. Here we use Schottky-gated heterostructures to probe the conducting layer at the interface between rubrene and PDIF-CN2 single crystals. Gate-modulated conductivity measurements demonstrate that interfacial transport is due to electrons, whose mobility exhibits band-like behavior from room temperature to ~ 150 K, and remains as high as ~ 1 cm2V-1s-1 at 30 K for the best devices. The electron density decreases linearly with decreasing temperature, an observation that can be explained quantitatively based on the heterostructure band diagram. These results elucidate the electronic structure of rubrene-PDIF-CN2 interfaces and show the potential of Schottky-gated organic heterostructures for the investigation of transport in molecular semiconductors.Comment: 37 pages, 9 Figures (including supplementary information

Donor-acceptor polymers for applications in organic electronics and photovoltaics

We have synthesized a new series of high-mobility polymeric semiconductors with good processability and excellent environmental stability for organic electronics and photovoltaics. Using these materials, solar cells were fabricated with power conversion efficiencies of up to 8.7% and remarkable fill factors of 76-80%.MINECO, Junta de Andalucí

Orientation-Dependent Electronic Structures and Charge Transport Mechanisms in Ultrathin Polymeric n-Channel Field-Effect Transistors

We investigated the role of metal/organic semiconductor interface morphology on the charge transport mechanisms and energy level alignment of the n-channel semiconductor poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P-(NDI2ODT2)). Variable-temperature study of well-ordered edge-on-oriented P(NDI2OD-T2) monolayer and multilayer field-effect transistors fabricated via Langmuir-Schafer (LS) method reveals a higher activation energy for the edge-on morphology when compared to that extracted for the face-on oriented P(NDI2OD-T2) spin-coated films, which showed a weaker temperature dependence. Near-ultraviolet inverse photoemission and low-energy electron transmission spectroscopies are utilized to study these rnicrostructurally defined polymeric films. The cross correlations of these techniques with the device characterization reveals the role of the molecular orientation at the semiconductor/contact interface in shifting the charge injection barrier. Finally, we demonstrate that the injection barrier for electrons is higher for the LS/edge-on than in the spin-coated/face-on films

Inorganic-organic hybrid thin-film transistors using inorganic semiconducting films

Inorganic semiconducting compounds, composites and compositions thereof, and related device structures

High-performance field effect transistors with self-assembled nanodielectrics

Field effect transistor devices comprising III-V semiconductors and organic gate dielectric materials, such dielectric materials as can afford flexibility in device design and fabrication

Organic Materials: The Effect of Subtle Modifications on Device Performance

In the search of new high-mobility polymeric semiconductors with good processability and excellent environmental stability, diverse synthetic strategies have been approached. One of the most widely used consists in the alternation of donor and acceptor moieties in the conjugated skeleton, which allows fine tuning of the polymer frontier molecular orbitals. For organic field effect transistors (OFETs) applications, low-lying HOMOs are essential to resist air oxidation and thus increase device stability. However, if the HOMO energy is too low, the resulting barrier to hole injection may compromise the transistor performance. Thus, a delicate balance between these two effects is needed. Furthermore, high performance solution-processable materials require the correct selection and positioning of the specific solubilizing substituents in order to achieve proper HOMO and LUMO energy levels, planar molecular conformations, close intermolecular π-π stacking, and proper thin film crystallinity. Following these two combined strategies, diverse polymeric materials with great performances in both OFETs and solar cells, and having remarkable air stability, have been synthesized and characterized. , This contribution will analyze how small modifications in their molecular structures can have a great impact on the device performance.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech