Dong-Seok Song

Numerical study on off-current features in an organic transistor by controlling electrode-overlap area

ABSTRACT We investigate the effect of the source/drain-to-gate electrode overlap area on the off-current features in organic thin-film transistors (OTFTs). For the numerical simulation, we used 2-D Atlas, a device simulator based on a two-dimensional Technology Computer Aided Design (TCAD) software tool provided by Silvaco. Both channel and overlap lengths are varied from 1 μm to 1000 μm. The off-current decreases with increasing channel length, whereas variations in the overlap area show a negligible effect on both on- and off-state currents.

Improvement of Current Efficiency at High Field Regime Via Description of Roll-off Characteristic in Model Device of OLEDs

We demonstrated the effect of the field dependency of charge carrier mobility on roll-off characteristic of current efficiency. Field dependent factor in Poole-Frenkel model is controlled to describe charge balance of electron and hole concentration at high field. It is well established that roll-off characteristic is dependent upon mobility match which results in charge balance in EML. We exhibited the improvement of the roll-off characteristic of current efficiency and explained how charge balance is induced through this description.

Relationship between initial and time-dependent cracks in charge transport of solution-processed organic thin-film transistor

ABSTRACT We report on the comprehensive effect of initial and time-dependent crack on the charge transport of 6, 13-bis (triisopropylsilyethynyl) pentacene (TIPS-PEN) thin-film transistors (TFTs) upon exposure to air. Among the two types of TIPS-PEN films, with and without initial thermal cracks, temporally generated cracks were found to be severely affected by the initial status of the thermal cracks upon air-exposure. After 12 months of air-exposure, the charge transport characteristics of TIPS-PEN TFTs with initial thermal cracks degraded up to 98%, while those without initial thermal cracks degraded only 88%. Based on our long-term experimental results, we conclude that the initial physical status of the cracks play a significant role in the growth of time-dependent cracks and the capability of charge transport in solution-processed TFTs.

Dependence of the hybrid solar cell efficiency on the thickness of ZnO nanoparticle optical spacer interlayer

ABSTRACT Optical spacer interlayers are commonly used in solar cells to improve the power conversion efficiency (PCE) of the device. This paper reports a study on the effect of zinc oxide (ZnO) optical spacer interlayer on PCPDTBT:ZnO hybrid solar cell. Optical spacers help to concentrate the spatial distribution of electric field due to light onto the active layer, and thus, improve the light absorption in the active layer. Finite-Difference Time-Domain (FDTD) calculations was carried out on stacked solar cell structure using a simulation software, Lumerical FDTD solutions. Maxwells equations were solved and the light absorbed by the active layer was computed. The design was optimized with regard to active layer thickness and ZnO optical spacer thickness.