HOMO, LUMO energy gap
The conjugated molecules are characterized by a small highest
occupied molecular orbital–lowest unoccupied molecular orbital
(HOMO–LUMO) separation, which is the result of a significant
degree of intra-molecular charge transfer (ICT) from the end-capping
electron-donor groups to the efficient electron-acceptor
groups through p-conjugated path. The strong charge transfer
interaction through p-conjugated bridge results in substantial