Polymer Electronics
(A
tutorial)
Conducting polymers behave as semiconductors
Applications: FET transistors (no doping)
Conventional Semiconductors: The top down approach
Conventional Semiconductors at the atomic level
When charge is moving the key word is mobility, mobility, mobility (cm2 V–1 s -1)
p-conjugated “polymers” (pentacene) at the molecular level
Consequences of molecular morphology in poly(3-alkylthiophenes)
Evolution of LED/OLED performance
A simple picture of
photophysics
in isolated molecules
A simple picture of intrachain photophysics for a conjugated polymer
Engineering where the energy goes in and where it comes out
Keys to conducting
polymer applications:
Synthetic
control and processibility
Self-Assembly (or … you I like, but you I hate)
For example: Self-assembly leads to ordered (lamellar) phases
“Self-assembly” leads to formation of helical phases
Side chain ordering does not always work in your favor!
Model depicting energy transfer from disordered to ordered phase
Back to electronic properties….
p-conjugated polymers have unusual charge excitations
Schematic representations of recombination pathways
Recombination is spin dependant
There is more to the singlet-triplet story
Electronic band structure in one-dimension: A primer
Tight-binding for p-electrons and semiconducting polymers
A one-dimensional chain (trans-polyacetylene)
After a simple approximation: [B(0) is approx. 1]
The Peierls instability (1939)
Conformational structure impacts electronic properties
Simple picture of polyacenes and poly-p-phenylenes
Now from the tight binding perspective
Poly-p-phenylene from tight binding
Impact of band structure on photocell device physics
A closer look at the calculation
Separating electrons and holes: A prerequisite for photovoltaic applications