De novo Design of Molecules with Low Hole Reorganization Energy Based on a Quarter-Million Molecule DFT Screen

​Nobuyuki Matsuzawa1,Hiroyuki Maeshima1,Hideyuki Arai1,Masaru Sasago1,Eiji Fujii1,Karl Leswing2,Mathew Halls2,Tim Robertson2,Kyle Marshall2,Joshua Staker2,Gabriel Marques2,Tsuguo Morisato2,David Giesen2,Alexander Goldberg2

​Materials exhibiting higher mobilities than conventional organic semiconducting materials (e.g. fullerenes and heteroacenes [1]), are in high demand for applications such as printed electronics. In order to explore new molecules in the heteroacene family that might show improved mobility, a massive theoretical screen of hole-conducting properties of molecules were performed using a cloud computing environment. Over 7,000,000 structures of fused furans, thiophenes and selenophenes were generated, and 250,000 structures were randomly chosen for subsequent DFT (Density Functional Theory) calculations of hole reorganization energies (λh). Utilizing the cloud-computed DFT dataset of a quarter-million reorganization energies, the de novo design method proposed by Gomez-Bombarelli [2] was applied to find further chemical structures with minimal reorganization energy. This method converts molecular structures into continuous variables by applying the variational autoencoder/decoder technique, which enables optimization of chemical structures in a continuous numerical space. Results of the inverse design showed that the method has the ability to generate exotic chemical matter, such as structures with a seven- and eight-membered rings, with reasonably low calculated reorganization energies.