Monte Carlo morphological modelling of a P3HT:PCBM bulk heterojunction organic solar cell

• Published in: Journal of polymer science. Part B, Polymer physics Vol. 53; no. 4; pp. 270 - 279
• Main Authors: Yap, Jing Han, To, Tran Thinh, Adams, Stefan
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley 15.02.2015; Blackwell Publishing Ltd; Wiley Subscription Services, Inc
• Subjects: annealing; bulk heterojunction; Computer simulation; crystals; dissociation; Dynamical systems; Dynamics; electrodes; heat treatment; Heterojunctions; Modelling; molecular dynamics; Monte Carlo method; Monte Carlo methods; Monte Carlo simulation; Morphology; P3HT:PCBM; phase separation; photovoltaic cells; polymers; solar cell; Solar cells; solar energy; surface area
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.23627

To deepen the understanding of morphology evolution in bulk heterojunction P3HT:PCBM organic photovoltaics system by thermal treatment, domain‐size‐dependent interfacial energies were first determined by coarse‐grained molecular dynamics modelling and then used in Monte Carlo simulations of the morphology evolution. Thereby initial conditions associated with optimal interfacial surface area, continuous volume, as well as domain sizes, and spatial distributions of the phase separated domains were identified. In line with earlier studies, a 1:1 P3HT:PCBM blend ratio is found to exhibit the most efficient morphology for exciton dissociation and charge transport. Our simulations reveal that preseeding of P3HT crystal at the anode side prior to the annealing process will be instrumental to pin the formation of P3HT at the favorable electrode especially when seeding exceeds a threshold of 10% surface coverage, whereas denser seeding patterns beyond the threshold did not improve the active layer morphology further. The observed trilayer depth profile (in the absence of preseeded P3HT crystals) implies that the commonly used thickness 100 nm of the active layer is not ideal for ensuring that donor and acceptor phases dominate at opposite ends of the active layer. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 270–279