Photoconductive sensors comprising dibromoanthanthrone (DBAA) were constructed aiming at the use in facsimile and digital copier machines.
Among four types of layer construction investigated, single layer sensor construction of DBAA dispersed in binder polymer gave a relatively high photocurrent(1.2×10
-5 A/10mm
2 at 5×10
4 V·cm
-1) as well as a very high photo-to-dark current ratio of 2.0×10
5, but showed a very poor response speed (rise time and decay time > 2000ms).
By adding styryl amine charge transporting material into the DBAA single layer photosensor, response speed was observed to be improved by a factor of 3 to 4×10
3 while photocurrent was diminished only by a factor of 11.
Electrode materials of single layer sensor construction were found to affect the dark current values. The effect of the electrode material was discussed in terms of the work function of the material. The potential barrier height for the injection of electron from the electrode to the DBAA photoconductive layer was found to determine the dark current of the photosensor.
The response speed improvement by the addition of carrier transporting material to the photosensitive DBAA layer was regarded as the result of the hole transport enhancement across the layer.
View full abstract