Enhanced charge mobility in a molecular hole transporter via addition of redox inactive ionic dopant: Implication to dye-sensitized solar cells

Abstract

Upon the addition of lithium salts to the hole-transporter matrix, 2, 2′, 7, 7′ -tetrakis (N,N -di- p -methoxypheny-amine)- 9, 9′ -spirobifluorene (spiro-MeOTAD), the authors observe a 100-fold increase in conductivity through spiro-MeOTAD within a Ti O2 mesoporous network. The authors demonstrate this to be a bulk effect and not due to improved injection at the electrodes. By testing "hole-only" diodes of pure spiro-MeOTAD and those doped with lithium salts, the authors calculate that the hole mobility increases from 1.6× 10-4 to 1.6× 10-3 cm2 V s. The authors discuss the possible mechanisms for this significant enhancement in charge mobility and its implication to the dye-sensitized solar cell operation. © 2006 American Institute of Physics.