Space-Charge Effects in CsI Electroluminescence

The photoemission at the metal-CsI crystal interface is examined at liquid-nitrogen temperature under square-wave excitation. The emission spectra of the initial flash and of the persistent luminescence are reported. The decays of the emissions just following the voltage application obey an inverse-power law. A qualitative interpretation of the initial brightness-wave behavior is obtained assuming the existence of traps with different capture cross sections. The brightness frequency dependence is interpreted assuming an exponential buildup of the space charge due to the injected carriers.