Modeling of current—voltage characteristics for double‐gate a‐IGZO TFTs and its application to AMLCDs

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92033/1/JSID20.5.237.pd

P‐102: Amorphous Silicon Thin‐Film Transistors‐based Active‐Matrix Organic Light‐Emitting Displays

In this paper, we describe hydrogenated amorphous silicon (a‐Si:H) thin‐film transistor (TFT)‐based active‐matrix arrays for active‐matrix organic light‐emitting displays (AM‐OLEDs). The proposed pixel electrode circuits based on three a‐Si:H TFTs can supply a continuous output current for AM‐OLEDs. Each pixel circuit has compensation circuits that can adjust for the OLED and a‐Si:H TFTs electrical characteristics shifts.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92089/1/1.1830416.pd

Microstructure characterization of amorphous thin solid films in a fringe-free environment

We have comprehensively analyzed the influence of the probe beam’s polarization state and incident angle on the vibrational absorption spectra of thin solid films such as hydrogenated amorphous silicon nitride and hydrogenated amorphous silicon in Fourier transform infrared spectroscopy. This analysis demonstrates the nuisance of interference fringes in distorting the bond structure of thin solid films in conventional vibrational absorption spectra. Based on the spectrum analysis and optical fundamentals, a practical method of recording a vibrational absorption spectrum of a thin solid film in an interference fringe-free environment is proposed. Furthermore, it is also demonstrated that a fringe-free spectrum can be recorded even in an interference-embedded environment if a right light incident angle is chosen. This interference-embedded fringe-free spectrum is only valid for material’s qualitative microstructure assessment but not for direct quantitative analysis. Finally, a comparison between ideal spectra and those fringe-corrected by conventional measures indicates a nontrivial discrepancy. Therefore, only interference-free spectrum exhibits the absolute features of the bond structures, and should be the standard spectrum used for thin solid film microstructure assessment.© 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71207/2/JAPIAU-85-1-388-1.pd

Ab initio electronic structure calculations of solid, solution-processed metallotetrabenzoporphyrins

An ab initio study of the electronic structures of solid metallotetrabenzoporphyrins (MTBPs) utilized in organic transistors and photovoltaics is presented. Bandstructures, densities of states, and orbitals are calculated for H2, Cu, Ni, and Zn core substitutions of the unit cell of solid TBP, as deposited via soluble precursors that are thermally annealed to produce polycrystalline, semiconducting thin-films. While the unit cells of the studied MTBPs are nearly isomorphous, substitution of the core atoms alters the structure of the bands around the energy bandgap and the composition of the densities of states. Cu and Ni core substitutions introduce nearly-dispersionless energy bands near the valence and conduction band edges, respectively, that form acceptor or deep generation/recombination states.Comment: 7 pages, 3 figures, 4 table

Integrating sphere charge coupled device-based measurement method for organic light-emitting devices

An integrating sphere charge coupled device (CCD)-based measurement system has been developed to accurately characterize the optoelectronic performance of organic polymer light-emitting devices (PLEDs). By theoretically analyzing a previously developed lens-coupled method and comparing it with the integrating sphere CCD-based method, we have found that the integrating sphere-based measurement method provides more stable reliable optical data in comparison with the lens-coupled measurement method. In addition, we demonstrate that inappropriate calibration of the PLED measurement system can greatly exaggerate device performance. © 2003 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71158/2/RSINAK-74-7-3572-1.pd

Observation of incident angle dependent phonon absorption in hydrogenated amorphous silicon nitride thin films

We have demonstrated the existence of longitudinal- and transverse-like optical modes of Si–N bond in vibrational absorption spectrum of hydrogenated amorphous silicon nitride thin films. One of the longitudinal-like optical resonances coincides with the transverse-like mode of Si–O bond, and the other closely neighbors the bending mode of N–H bond. We have also shown that the conventionally assigned asymmetric stretching mode of Si–N bond is merely a transverse-like mode of the bond. The microstructures of both longitudinal- and transverse-like modes can well be apprehended by a p-polarized beam at an oblique incidence light, especially at Brewster angle incidence. The spectrum distortion induced by interference fringes can be eliminated at this condition. © 1998 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70219/2/APPLAB-73-26-3866-1.pd

Amorphous In–Ga–Zn–O thin‐film transistor active pixel sensor x‐ray imager for digital breast tomosynthesis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134962/1/mp2382.pd

4.4: 200 dpi 3‐a‐Si:H TFTs Voltage‐Driven AM‐PLEDs

In this paper we describe opto‐electronic properties of 200 dpi 3‐a‐Si:H TFT voltage‐driven AM‐PLEDs. In this display design the output current level drifts induced by either process variations or device aging can be reduced by adjusting the driver a‐Si:H TFT operating point with the active resistor. Our first green lightemitting AM‐PLED prototype had brightness of 50 cd/m 2 and fill factor of about 45%.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92132/1/1.1832196.pd

Light output measurements of the organic light-emitting devices

In this article we describe a novel light output measurements method of the organic light-emitting devices (OLEDs). This method not only provides the electroluminescence (EL) spectral response of the OLEDs, but also gives the spectral distribution of the radiant power (W), luminance (cd/m2),(cd/m2), luminous flux (lm), and photon emission of the measured light-emitting object. Also an accurate calculation method of the OLED EL external quantum efficiency is proposed. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70764/2/RSINAK-71-5-2104-1.pd

Field-effect mobility of polycrystalline tetrabenzoporphyrin thin-film transistors

A possible relation between a thin-film microstructure and an organic thin-film field-effect transistor (OFET) behavior is discussed in terms of nonlinearity in the extraction of the device electrical parameters. Staggered source and drain electrode OFETs were fabricated using a soluble precursor form of the organic small molecule semiconductor tetrabenzoporphyrin, and characterized using linear and nonlinear best-fit methods. Linear best-fit models overestimated the field-effect mobility and accumulation threshold voltage when compared to a nonlinear best-fit model that accounts for dispersive charge-carrier transport. The deviation between the methods is found to be consistently less than that for polymer OFETs, as indicated by smaller nonlinearity factors of γ = 1.2γ=1.2 and 1.7 in the linear and saturation regimes, respectively. The nonlinear field-effect mobility exhibits a sublinear gate-bias dependence wherein the mobility increases at a slower rate in strong accumulation than near threshold. Furthermore, nonlinear curve fitting indicates lower trap characteristic temperatures as compared to polymer OFETs, and a relatively moderate density of grain-boundary trap states localized at the dielectric interface and in the bulk to be filled before accumulation-related conduction dominates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87400/2/014503_1.pd