Optimization and Validation of Efficient Models for Predicting Polythiophene Self-Assembly

Abstract

We develop an optimized force-field for poly(3-hexylthiophene) (P3HT) and demonstrate its utility for predicting thermodynamic self-assembly. In particular, we consider short oligomer chains, model electrostatics and solvent implicitly, and coarsely model solvent evaporation. We quantify the performance of our model to determine what the optimal system sizes are for exploring self-assembly at combinations of state variables. We perform molecular dynamics simulations to predict the self-assembly of P3HT at ∼ 350 combinations of temperature and solvent quality. Our structural calculations predict that the highest degrees of order are obtained with good solvents just below the melting temperature. We find our model produces the most accurate structural predictions to date, as measured by agreement with grazing incident X-ray scattering experiments.

Tying Together Multiscale Calculations for Charge Transport in P3HT: Structural Descriptors, Morphology, and Tie-Chains

“…In previous work, we predicted equilibrium morphologies of P3HT at ∼ 100 combinations of temperature, T, and solvent strength, ε s [12]. Each of these model systems is monodisperse, with Figure 2b.…”

“…The P3HT morphologies studied here were previously predicted using MD simulations, and so only salient information will be covered here [12]. We investigate ∼ 100 morphologies generated from simulations using an adapted Optimized Performance for Liquid Simulations -United Atom forcefield to govern the non-bonded pair interactions (see Figure 1b) 2).…”

“…In order to successfully evaluate structure-performance relationship, we require a performance descriptor that can quantifiably describe morphologies. One such property is the charge-carrier [12] with authors' permission.) mobility, µ, which describes the speed that electrons and holes conduct through the semiconducting layer.…”

“…Color bars are normalized to the maximum value of each parameter. (a) The structural order of each system given by the order parameter, ψ, as in the previous work (Figure replicatedfrom[12] with authors' permission). (b) The hole mobility, µ 0 , varying between red (∼ 0.15 cm 2 /Vs) and blue (∼ 0.01 cm 2 /Vs) There is not a perfect mapping between ψ and µ 0 -lower and higher temperature systems have higher and lower µ 0 respectively, which is not captured effectively by ψ.…”