Efficient Computational Screening of Organic Polymer Photovoltaics

Abstract

There has been increasing interest in rational, computationally driven design methods for materials, including organic photovoltaics (OPVs). Our approach focuses on a screening "pipeline", using a genetic algorithm for first stage screening and multiple filtering stages for further refinement. An important step forward is to expand our diversity of candidate compounds, including both synthetic and property-based measures of diversity. For example, top monomer pairs from our screening are all donor-donor (D-D) combinations, in contrast with the typical donor-acceptor (D-A) motif used in organic photovoltaics. We also find a strong "sequence effect", in which the average HOMO-LUMO gap of tetramers changes by ∼0.2 eV as a function of monomer sequence (e.g., ABBA versus BAAB); this has rarely been explored in conjugated polymers. Beyond such optoelectronic optimization, we discuss other properties needed for high-efficiency organic solar cells, and applications of screening methods to other areas, including non-fullerene n-type materials, tandem cells, and improving charge and exciton transport.

Effect of the length of alkyl side chains in the electronic structure of conjugated polymers

“…Molecular modeling of conjugated polymers has been a challenge for the scientific community for several reasons, for example, the fact that they are large molecules and thus easily deformable and the presence of side chains 2 . Several theoretical studies of these materials have been conducted based on quantum or classical mechanics [8][9][10][11][12][13] , but the number of variables that must be taken into account in any model carries a high computational cost 8 . Thus, it is necessary to find ways to reduce this cost to simulate these materials without compromising the quality of results.…”

Conjugated Polymer Photovoltaic Materials

“…The rapid progress in novel conjugated photovoltaic polymers demonstrates that there is plenty of room to bring the cost of PSCs down by developing low-cost and highly efficient polymeric photovoltaic materials [183,184]. Guided by computational calculations and screening [185], further improvements will be realized in the near future by fine optimization of integrated backbones, side chains, and molecular weight [186] based on well-defined highly efficient polymers.…”

What Is High-Throughput Virtual Screening? A Perspective from Organic Materials Discovery

“…For instance, using constrains based on synthetic accessibility, O'Boyle et al reduced a set from potentially 800 million combinations to a mere 60 thousand in a search for organic photovoltaic materials. (32,33) There is, however, a tradeoff to encoding these soft constraints into hard algorithmic rules: since only what is in the library gets to be screened, one risks leaving out of the process molecules that are harder to make but perhaps have game-changing properties: the high-risk high-reward scenario. It would be desirable then, to assess synthetic availability just like any other property along its own scale, and molecules can be judged globally.…”