Generation and recombination of charge carriers in p-terphenyl crystal. Photoionization of singlet exciton

With two-color photoionization, by using a nitrogen laser and a dye laser, it is shown that photoionization of singlet excitons in p-terphenyl crystal occurs with a photoionization cross section of (5.2±1.6)×10−19 cm2 with 590 nm photons (at 5×104 V/cm). Volume recombination of electrons and holes sets in at higher excitation intensities. The recombination rate constant γeh is found to be (1.3±0.4)×10−6 cm3 s−1. The understanding of the transient current pulse shape allows an in situ determination of the penetration depth of the exciting light, with a consequent improvement in the reliability of the constants determined.