Investigation on hole drift mobility in poly(n-hexylphenylsilane)

The hole drift mobility in poly(n-hexylphenylsilane) (PHPS) was observed over an extended range of temperature and field by DC time-of-flight technique. The value of the hole drift mobility in PHPS decreases monotonically from 6×10−3 to 7×10−4 cm2/V s with an increase in the field from 3×102 to 8×102 V/cm. A negative differential conduction model giving a good interpretation for the decrease in the mobility. The value of mobility was quantitatively analyzed based on Bässlerʹs disorder formalism, giving a very small value of σ=0.042 eV in spite of the relatively large value of Σ=3.3. The polaron formation energy was also estimated to be Ep=0.058 eV using the Bässler–Borsenbergerʹs equation. This value is very small value in comparison to that in poly(methylphenylsilane) (PMPS) and reflects that the backbone in PHPS is more tightly locked than that in PMPS.