Yi-Min Chin

Enhancement of photocurrent of poly(3-hexylthiophene)/n-type Si diodes by incorporating the reduced graphene oxide sheets

In this study, the effect of the incorporation of the reduced graphene oxide (RGO) sheets into poly(3-hexylthiophene) (P3HT) on photocurrent in the RGO-doped P3HT/n-type Si diode was examined. Photocurrent proportional to RGO doping was observed. Charge detrapping phenomena are studied through time domain measurement for P3HT-based thin-film transistors. Results revealed that RGO influences the photoresponse by increasing the number of the trapped electrons in RGO as well as providing additional holes that serve to reduce the photocurrent time constant. High responsivity thus originates from efficient light absorption and carrier collection.

Low-resistance nonalloyed ohmic contacts on undoped ZnO films grown by pulsed-laser deposition

We report on the formation of nonalloyed Ti and Ni ohmic contacts to ZnO films grown by pulsed-laser deposition. The experimental results show a lower barrier height of the Ti/ZnO samples than that of the Ni/ZnO samples (due to the lower work function of Ti than Ni), suggesting the Fermi-level unpinning at the interfaces. Based on the thermionic-emission or the thermionic-field-emission model, we found weak barrier-height dependence of the contact resistivity, implying that the presence of hydroxide in ZnO (i.e. the formation of the narrow depletion region at the metal/ZnO interface) resulted in the excess current component related to tunnelling, which led to the formation of the low-resistance nonalloyed metal/ZnO contact. The measurement temperature dependence of the contact resistivity revealed that the dominant current transport mechanism is field emission.

Correlation between the electron-phonon coupling and rectifying performance for poly(3-hexylthiophene)/n-type Si devices

A correlation between the electron-phonon coupling and rectifying performance is identified for poly(3-hexylthiophene) (P3HT)/n-type Si devices and an analysis using the temperature-dependent Hall-effect characteristics is presented. The carrier mobility in the P3HT film exhibits strong temperature dependence, indicating the dominance of tunneling. However, the incorporation of titanium oxide (TiO2) nanoparticles into P3HT leads to the dominance of hopping. The results demonstrate that the incorporation of TiO2 nanoparticles into P3HT influences the electrical property of P3HT/n-type Si devices by the electron-phonon coupling modification and the increased spacing between molecules that serve to enhance the carrier mobility in P3HT.

Electron-phonon coupling modification and carrier mobility enhancement in poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) films by ultraviolet irradiation

The effect of ultraviolet irradiation on the electrical property of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) films was examined. It is shown that the carrier mobility increases while the carrier density does not change substantially. The carrier mobility in PEDOT:PSS samples exhibits strong temperature dependence, indicating the dominance of tunneling (hopping) at low (high) temperatures. The results demonstrate that changes in the chemical structure may lead to the modification of the electron-phonon coupling, thus increasing the carrier mobility in PEDOT:PSS.

Hysteresis mechanism in current?voltage characteristics of ZrOx films prepared by the sol?gel method

In the study, ZrOx films were deposited on substrates by the sol?gel technique. X-ray photoelectron spectroscopy, x-ray diffraction, photoluminescence and conductivity measurements were used to characterize the films. The authors found that the displacement current of oxygen-rich ZrOx films was smaller than that of oxygen-deficient ZrOx films. According to the experimental results, the authors suggested that donor-like oxygen-vacancy related and crystallographic defects within the ZrOx film controlled carrier flow and resulted in hysteresis-type current?voltage characteristics of indium tin oxide/ZrOx/Au devices.