Why ultrafast charge separation occurs in bulk-heterojunction organic solar cells: a multichain tight binding model study.Bulk-heterojunction (BHJ) organic solar cells (OSCs) exhibit ultrafast charge separation (UCS) which enables lower geminate charge recombination and high internal quantum efficiency. 
multichain tight binding model
In this work, we build a multichain tight-binding model to study the conditions for realizing UCS. 
tight-binding model