Biomedical subjects

N Tessler

Publications and source records attributed to N Tessler.

4 recordsLinked to original sources

PubMed2005

Direct determination of the hole density of states in undoped and doped amorphous organic films with high lateral resolution.

We investigate the density of states (DOS) for hole transport in undoped and doped amorphous organic films using high lateral resolution Kelvin probe force microscopy. Measurements are done on field effect transistors made of N,N1-diphenyl-N, N1-bis(1-naphthyl)-1,10-biphenyl-4,4II-diamine undoped or p doped with tetrafluoro-tetracyanoquinodimethane. We determine the DOS structure of the undoped material, including an anomalous peak related to interfaces between regions of different surface potential, the DOS doping-induced broadening, and doping-induced sharp peaks on the main DOS distribution.

Journal Article↗

PubMed2000

Electric field distribution in polymer light-emitting electrochemical cells

We use electroabsorption spectroscopy and modeling studies to probe the electric field in light-emitting electrochemical cells. At room temperature and constant applied bias, the steady-state internal field is zero for a range of biases. However, when the ions are frozen in place by cooling under steady bias, and the bias is subsequently changed, the profile of the electric potential resembles a typical p-n junction.

Journal Article↗

PubMed1999

All-polymer optoelectronic devices

Composites of nanoparticles and conjugated polymers that exhibit composition-tunable optical constants have been developed for use in semiconducting photonic structures. For example, the 550-nanometer wavelength in-plane refractive index of poly(p-phenylenevinylene)-silica composites can be tailored over the range of 1.6 to 2.7, allowing efficient distributed Bragg reflectors and waveguides to be fabricated. Low levels of chemical doping improve electrical conductivity through these structures without detriment to their photonic properties. Exemplifying these concepts, all-polymer microcavities and microcavity light-emitting diodes were demonstrated. Appropriate confinement of photons and electron-hole pairs in these organic semiconductor-based structures can be achieved.

Journal Article↗

PubMed1998

Integrated optoelectronic devices based on conjugated polymers

An all-polymer semiconductor integrated device is demonstrated with a high-mobility conjugated polymer field-effect transistor (FET) driving a polymer light-emitting diode (LED) of similar size. The FET uses regioregular poly(hexylthiophene). Its performance approaches that of inorganic amorphous silicon FETs, with field-effect mobilities of 0.05 to 0.1 square centimeters per volt second and ON-OFF current ratios of >10(6). The high mobility is attributed to the formation of extended polaron states as a result of local self-organization, in contrast to the variable-range hopping of self-localized polarons found in more disordered polymers. The FET-LED device represents a step toward all-polymer optoelectronic integrated circuits such as active-matrix polymer LED displays.

Journal Article↗