Charge-transfer-state energy reduction at various donor/acceptor interfaces

Organic solar cells have several properties that make them desirable over inorganic solar cells such as cost-effectiveness, flexibility, and lightweight. While organic solar cells tend to exhibit energy losses due to the need to break up charge-transfer (CT) states, a phenomenon that does not exist in its inorganic counterparts, highly-crystalline rubrene is a donor that has been shown to allow for delocalized CT states. This project aimed to examine the effects of the acceptor choice in the delocalization of charge transfer states by examining the energies of these states in the acceptors Cl₆-subPc-Cl and Cl₁₂-subPc-Cl. We found that the CT state energy dropped by 0.25 eV when going from amorphous to crystalline rubrene with Cl₆-subPc-Cl as the acceptor. The CT state energy dropped by 0.38 eV when going from amorphous to crystalline rubrene with Cl₁₂-subPc-Cl, which compares to the energy drop of 0.38 eV observed with C₆₀ as the acceptor. This indicates that the choice of acceptor does have an impact on the CT-state energies.