Photoconductivity in organic TPD films: Effects of photoadsorption of O2 and N2

Abstract Steady state photoconductivity of disordered tri-methylphenyl diamine (TPD) films has been studied in vacuum, oxygen, and nitrogen atmospheric conditions, at temperature range between 210 and 300 K. The temperature T and intensity (number of absorbed photon) G dependence of photoconductivity is proportional to Gγexp [−(σ/kT)2/2] with γ = 0.2–0.5 and σ = 0.06–0.08 eV in vacuum condition. The photocurrent increases with exposing O2 or N2 (4 and 10 kPa), without changing the values of σ and γ. These changes are reversible in nature (photoadsorption), i.e. after stopping exposure and out gassing of O2 or N2, the photocurrent returns to the original state in the vacuum condition. The magnitude of change of the photocurrent in O2 exposure is larger than that in N2. The dynamics of photocarriers with O2 or N2 exposure is discussed.