Origin of Radiation Induced Damage in Organic P3HT:PCBM Based Photocells

Organic semiconductor photocells based upon P3HT:PCBM (1:1 by weight) have been subjected to X irradiation. The carrier lifetime has been determined using a pulsed optical method with continuous light to generate an open circuit voltage bias. No effect is observed on the carrier lifetime up to 300 krad (SiO
₂
). However, changes in the open circuit voltage are observed and we argue that these result from compensation of the internal field which results from the built-in potential. The origin of the field modifications must lay in the presence of radiation induced trapped charge near the organic semiconductor/anode and/or cathode interfaces.