Developing Efficient Small Molecule Acceptors with sp² -Hybridized Nitrogen at Different Positions by Density...

Area of Science:

• Materials Science
• Computational Chemistry
• Organic Electronics

Background:

• The performance of organic solar cells (OSCs) is critically dependent on the chemical structure of small molecule acceptors.
• Rational design strategies are needed to optimize acceptor performance, moving beyond trial-and-error approaches.

Purpose of the Study:

• To investigate the impact of sp²-hybridized nitrogen substitution at various positions (core, side chain, terminal) of small molecule acceptors.
• To computationally model and predict the performance of novel small molecule acceptors for OSCs.

Main Methods:

• Multiscale computational modeling, including quantum chemical analysis and molecular dynamics simulations.
• Machine learning was employed for predicting power conversion efficiency (PCE).
• Calculations of electron-reorganization energy, transfer integral, excited state behavior, and Flory-Huggins parameter were performed.

Main Results:

• Nitrogen substitution at the terminal group significantly reduced electron-reorganization energy, a key factor for improved electron mobility.
• Substitutions did not substantially alter transfer integrals or excited state properties.
• Molecular dynamics and Flory-Huggins parameter calculations indicated favorable miscibility and packing with the PBDB-T polymer donor for specific nitrogen-substituted acceptors (N3 and N4).

Conclusions:

• Nitrogen substitution at the end-capping position of small molecule acceptors is an effective strategy for enhancing electron mobility and designing efficient organic solar cells.
• Computational modeling provides a valuable tool for accelerating the discovery of high-performance organic electronic materials.