From c2a08c2b580ddf5002012d6149b9ff7a4e20a00e Mon Sep 17 00:00:00 2001 From: Blaise Thompson Date: Mon, 26 Feb 2018 10:27:18 -0600 Subject: 2018-02-26 10:27 --- PEDOT:PSS/chapter.tex | 170 +++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 169 insertions(+), 1 deletion(-) (limited to 'PEDOT:PSS/chapter.tex') diff --git a/PEDOT:PSS/chapter.tex b/PEDOT:PSS/chapter.tex index c7dc807..9138972 100644 --- a/PEDOT:PSS/chapter.tex +++ b/PEDOT:PSS/chapter.tex @@ -1 +1,169 @@ -\chapter{PEDOT:PSS} \ No newline at end of file +\chapter{PEDOT:PSS} + +\section{Introduction} + +Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is a transparent, electrically +conductive (up to 4380 S cm$^{-1}$ \cite{KimNara2013a}) polymer. % +It has found widespread use as a flexible, cheap alternative to inorganic transparent electrodes +such as indium tin oxide. % + +As a polymer, PEDOT:PSS implicitly contains a large amount of structural inhomogeneity. % +On top of this, PEDOT:PSS is a two component material, composed of PEDOT (low molecular weight, +p-doped, highly conductive) and PSS (high molecular-weight, insulating, stabilizing). % +These two components segment into domains of conductive and non-conductive material, leading to +even more structural inhomogeneity. % +Nonlinear spectroscopy may be able to shed light on the microscopic environment of electronic +states within PEDOT:PSS. % + +\section{Background} + +Complex microstructure: +\begin{enumerate} + \item PEDOT oligomers (6---18-mers) + \item these oligomers $\pi$-stack to form small nanocrystalites, 3 to 14 oligomers for pristine + films to as many as 13---14 oligomers for more conductive solvent treated films + \item nanocrystallites then arrange into globular conductive particles in a pancakge-like shape + \item these particles themselves are then linked via PSS-rich domains and assembled into + nanofibril geometry akin to a string of pearls + \item nanofibrils interweave to form thin films, with PSS capping layer at surface +\end{enumerate} + +Prior spectroscopy (absorption anisotropy, X-ray scattering, condutivity). % + +% TODO: absorption spectrum of thin film + +Broad in the infrared due to midgap states created during doping from charge-induced lattice +relaxations. % +These electronic perturbations arise from injected holes producing a quinoidal distortion spread +over 4-5 monomers of the CP aromatic backbone, collectively called a polaron. % +Energetically favorable to be spin-silent bipolaron. % + +\section{Methods} + +PEDOT:PSS (Orgacon Dry, Sigma Aldrich) was dropcast onto a glass microscope slide at 1 mg/mL at a +tilt to ensure homogeneous film formation. % +The sample was heated at 100 $^\circ$C for $\sim$15 min to evaporate water. % + +An ultrafast oscillator (Spectra-Physics Tsunami) was used to prepare $\sim$35 fs seed pulses. % +These were amplified (Spectra-Physics Spitfire Pro XP, 1 kHz), split, and converted into 1300 nm 40 +fs pulses using two separate optical parametric amplifiers (Light Conversion TOPAS-C): ``OPA1'' and +``OPA2''. % +Pulses from OPA2 were split again, for a total of three excitation pulses: $\omega_1$, $\omega_2$ +and $\omega_{2^\prime}$. % +These were passed through motorized (Newport MFA-CC) retroreflectors to control their relative +arrival time (``delay'') at the sample: $\tau_{21} = \tau_2 - \tau_1$ and $\tau_{22^\prime} = +\tau_2 - \tau_{2^\prime}$. The three excitation pulses were focused into the sample in a $1^\circ$ +right-angle isoceles triange, as in the BOXCARS configuration. \cite{EckbrethAlanC1978a} % +Each excitation beam was 67 nJ focused into a 375 $\mathsf{\mu m}$ symmetric Gaussian mode for an +intensity of 67 $\mathsf{\mu J / cm^2}$. % +A new beam, emitted coherently from the sample, was isolated with apertures and passed into a +monochromator (HORIBA Jobin Yvon MicroHR, 140 mm focal length) with a visible grating (500 nm blaze +300 groves per mm). % +The monochromator was set to pass all colors (0 nm, 250 $\mathsf{\mu m}$ slits) to keep the +measurement impulsive. % +Signal was detected using an InSb photodiode (Teledyne Judson J10D-M204-R01M-3C-SP28). % +Four wave mixing was isolated from excitation scatter using dual chopping and digital signal +processing. % + +\section{Transmittance and reflectance} + +\afterpage{ +\begin{figure} + \centering + \includegraphics[width=0.5\linewidth]{"PEDOT:PSS/linear"} + \caption[PEDOT:PSS transmission and reflectance spectra.]{ + Thin film spectra. + Transmission, reflectance, and extinction spectrum of the thin film used in this work. % + Extinction is $\log_{10}{\mathsf{(transmission)}}$. % + } + \label{fig:PEDOTPSS_linear} +\end{figure} +\clearpage} + +\autoref{fig:PEDOTPSS_linear} shows the transmission, reflectance, and extinction spectrum of the +thin film used in this work. % + +\section{Three-pulse echo spectroscopy} + +\afterpage{ +\begin{figure} + \centering + \includegraphics[width=0.5\linewidth]{"PEDOT:PSS/mask"} + \caption[PEDOT:PSS 3PE phase matching mask.]{ + Phase matching mask used in this experiment. + Each successive ring subtends 1 degree, such that the excitation pulses are each angled one + degree relative to the mask center. + The two stars mark the two output poyntings detected in this work. + } + \label{fig:PEDOTPSS_mask} +\end{figure} +\clearpage} + +Two dimensional $\tau_{21}, \tau_{22^\prime}$ scans were taken for two phase matching +configurations: (1) $k_{\mathsf{out}} = k_1 - k_2 + k_{2^\prime}$ (3PE) and (2) $k_{\mathsf{out}} = +k_1 + k_2 - k_{2^\prime}$ (3PE*). % +The rephasing and nonrephasing pathways exchange their time dependance between these two +configurations. % +Comparing both pathways, rephasing-induced peak shifts can be extracted as in 3PE. [CITE] % +All data was modeled using numerical integration of the Liouville-von Numann equation. % + +Continuously variable ND filters (THORLABS NDC-100C-4M, THORLABS NDL-10C-4) were used to ensure +that all three excitation pulse powers were equal within measurement error. % + +\afterpage{ +\begin{figure} + \centering + \includegraphics[width=0.5\linewidth]{"PEDOT:PSS/raw"} + \caption[PEDOT:PSS 3PE raw data.]{ + CAPTION TODO + } + \label{fig:PEDOTPSS_raw} +\end{figure} +\clearpage} + + +\afterpage{ +\begin{figure} + \centering + \includegraphics[width=0.5\linewidth]{"PEDOT:PSS/processed"} + \caption[PEDOT:PSS 3PE processed data.]{ + CAPTION TODO + } + \label{fig:PEDOTPSS_processed} +\end{figure} +\clearpage} + +\afterpage{ +\begin{figure} + \centering + \includegraphics[width=0.5\linewidth]{"PEDOT:PSS/delay_space"} + \caption[PEDOT:PSS 3PE delay space.]{ + CAPTION TODO + } + \label{fig:PEDOTPSS_delay_space} +\end{figure} +\clearpage} + +\afterpage{ +\begin{figure} + \centering + \includegraphics[width=0.5\linewidth]{"PEDOT:PSS/traces"} + \caption[PEDOT:PSS 3PE traces.]{ + CAPTION TODO + } + \label{fig:PEDOTPSS_traces} +\end{figure} +\clearpage} + +\afterpage{ +\begin{figure} + \centering + \includegraphics[width=0.5\linewidth]{"PEDOT:PSS/overtraces"} + \caption[PEDOT:PSS 3PE traces.]{ + CAPTION TODO + } + \label{fig:PEDOTPSS_overtraces} +\end{figure} +\clearpage} + +\section{Frequency-domain transient grating spectroscopy} \ No newline at end of file -- cgit v1.2.3