Real and Apparent Photoconduction in Single Crystals of Methyltriphenylphosphonium (TCNQ)2−

Photocurrents in single crystals and compressed discs of methyltriphenylphosphonium (TCNQ)2− can be observed at low temperatures where the dark current is greatly reduced, or by the use of a chopped light source and a narrow band amplifier or oscilloscope display. By chopping at appropriate frequencies the true photocurrent can be observed and bolometric effects eliminated. The true photocurrent, which is ohmic and linear with light intensity, shows a threshold at (2.7 ± 0.1) μm. The carrier lifetime is 140 ms above and below the phase change at 310 K, but at the phase change more than one lifetime is observed due to trapping.