Sam Foster, James Kirkpatrick, Thomas Kirchartz, Jenny Nelson Imperial College London [email protected] MRS Boston Fall 2012 O8.08 – Wednesday 28th November

→ HOMO 'for free' (well defined in KS DFT) → LUMO Needs care (don't use KS virtual orb.) → Absorption Spectra TD-DFT (comp. Intensive) → Estimate Mobility: (Need packing structure) Inner Sphere Reorg. Energy (easy) Outer Sphere Reorg. Energy (???) Transfer Integrals (researcher time intensive) Kinetic Monte Carlo (ToFeT, other codes) Create model of Density of States: → continuum device modelling, transport behaviour

→ HOMO 'for free' (well defined in KS DFT) → LUMO Needs care (don't use KS virtual orb.) → Absorption Spectra TD-DFT (comp. Intensive) → Estimate Mobility: (Need packing structure) Inner Sphere Reorg. Energy (easy) Outer Sphere Reorg. Energy (???) Transfer Integrals (researcher time intensive) Kinetic Monte Carlo (ToFeT, other codes) Create model of Density of States: → continuum device modelling, transport behaviour

0. ] [ J S J 0. ] [ 0. J S J ] [ 0. 0. J S ]] H = Hamiltonian very easy to solve Parameters semi-empirical (can derive from DFT) Can treat extremely large systems

Mose Casalegno, Guido Raos, Stefano V. Meille, and Riccardo Po ̀ The Journal of Physical Chemistry B 2010 114 (4), 1591-1602 40 independent copies of a 16-mer P3HT Packed Loosely in a (10nm)^3 box Equilibrated for 1ns under 1.atm with a thermostat

efficiency, transient photocurrent at short times) E ~ 60 meV (further inside the bandgap, at longer time scales, which would explain charge extraction measurements and transient photocurrent at longer timescales) Modelling directly produces a realistic DoS Suggests that inter-monomer torsional disorder dominates density of states ! Note that the extended regions of conjugation are traps !

effectively β corresponds to crystallization in one dimension, a remarkably uncommon phenomenon in nature." http://pubs.acs.org/doi/pdfplus/10.1021/nl071207u

normal distribution (around 45 degree minima) Consider beta phase to be small pockets of flat regions of polymer – (i.e. J is maximised is these regions to J0)

torsion sufficient to describe DoS – In PFO, natural background twist makes extended regions (Beta phase) deep traps – Traps are not always what one imagines (and be careful what you wish for) Even (or especially?) 1930s electronic-structure techniques can offer useful insights

Sam Foster, James Kirkpatrick, Thomas Kirchartz, Jenny Nelson Imperial College London [email protected] Acknowledgements: Sumitomo, Donal Bradley, Boon Kar Yap, EPSRC (Scallops Project)

→ HOMO 'for free' (well defined in KS DFT) → LUMO Needs care (don't use KS virtual orb.) → Absorption Spectra TD-DFT (comp. Intensive) → Estimate Mobility: (Need packing structure) Inner Sphere Reorg. Energy (easy) Outer Sphere Reorg. Energy (???) Transfer Integrals (researcher time intensive) Kinetic Monte Carlo (ToFeT, other codes)