Analysis of hole mobility of fluorene derivative films based on the Disorder Model and relationship between disorder free mobility and reorganization energy in the Marcus theory

摘要

Hole transporting behavior of two fluorene derivatives having carbazole group (2C1CBz) and diphenyl amino group (2C1DAF) and a carbazole derivative (C2CBzCBz) were investigated. Further, the fluorene derivatives and typical hole-transporting materials, 4,4'-bis[N-(p-tolyl)-N-phenyl-amino] biphenyl (TPD) and 4,4'-Bis(carbazol-9- yl)biphenyl (CBP) was analyzed based on the Gaussian Disorder Model. At room temperature, amorphous film of 2C1CBz exhibited highest hole mobility of 3.1 x 10~(-3) Vcm~2/Vs at 1.6 x 10~5 Vcm~(-1) in these materials. From analysis based on the Gaussian Disorder Model, however, amorphous film of CBP is indicated to have highest disorder free mobility; the values of 2C1CBz, 2C1DAF, CBP and TPD were 0.812, 0.092, 2.84, and 0.38 cm~2/Vs, respectively. In addition, their reorganization energy l was evaluated by a quantum mechanical calculation with ADF (Amsterdam Density Functional package, Scientific Computing & Modeling Co.) based on the Marcus theory. The experimental and calculation results demonstrated that the μ_0 has good proportionality relation with the λ. Because the μ_0 mean as a rough standard of carrier-transporting, this result suggest that evaluation of λ may be a promising approach to design molecular structure of carrier transporting materials with high carrier mobility.