Extended Conjugation Length of Nonfullerene Acceptors with Improved Planarity via Noncovalent Interactions for High-Performance Organic Solar Cells

摘要

Three low-bandgap nonfullerene acceptors (NFAs) IDTO-T-4F, IDTO-Se-4F, and IDTO-TT-4F with extended conjugation length are designed and synthesized. Various pi-spacers, thiophene, selenophene, and thieno[3,2-b]thiophene are incorporated to extend the conjugated length and enhance the backbone planarity via noncovalent O center dot center dot center dotboldS or O center dot center dot center dot Se interactions/bold. These NFAs exhibit strong light absorption in the range of 600-900 nm with narrow bandgaps between 1.38 and 1.45 eV. By blending with a wide-bandgap donor material PBDB-T, organic solar cells (OSCs) based on these NFAs all yield high efficiency over 10% with low energy losses ranging from 0.52 to 0.59 eV. Importantly, as a result of relatively high lowest unoccupied molecular orbital level, large hole and electron mobility in blend film, and low charge carrier recombination loss, optimized devices based on IDTO-T-4F exhibit a large open-circuit voltage of 0.864 V, a high short-circuit current density of 20.12 mA cm(-2), and a notable fill factor of 72.7%, leading to an impressive efficiency of 12.62%, which represents the best performance for NFA OSCs using noncovalent interactions in acceptor molecule design. The results indicate that optimizing the conjugation length and backbone planarity via intramolecular noncovalent O center dot center dot center dotboldS or O center dot center dot center dot Se interactions is a useful strategy for NFA materials invention toward high/bold-performance solar cells.