Modeling of the X-irradiation Response of the Carrier Relaxation Time in P3HT:PCBM Organic-Based Photocells

Initial experimental work has demonstrated that x-ray bombardment of organic-based photocells (specifically P3HT:PCBM-based) leads to a reduction in the open-circuit voltage (
V
_oc
) without apparent change in the carrier relaxation time. The variation of
V
_oc
was suggested to be due to the injection and trapping of holes near the anode, which resulted in a decrease in the built-in potential. We have extended the experimental measurements to higher total dose (~1300 krad(SiO
₂
)). Using standard inorganic modeling tools, a device model of the organic cell has been developed and predictions made. These predictions have been compared to the results of the previous and new experimental measurements and they demonstrate reasonable agreement between the two, thereby supporting the initial charge buildup hypothesis. Questions about the origin and behavior of the photo-carrier relaxation arise.