Understanding the open-circuit voltage of organic photovoltaic devices with donor deposited at different deposition rate

This report demonstrated that the open-circuit voltage (V
_OC
) of organic photovoltaic devices could be altered by changing the deposition rate of donor. The V
_OC
was higher when used a higher deposition rate of donor. Atomic force microscopic image of donor thin film showing the presence of pinholes indicated the strong molecular interaction at the lower deposition rate. These may cause a severe leakage current from acceptor to anode as observed in the dark current. Equivalent circuit model and temperature-dependent dark currents were utilized to realize the effect of reverse saturation current on V
_OC
. The higher barrier height at the donor-acceptor interface was attributed to the improved V
_OC
for the device with higher donor deposition rate.