On the dependency of equivalent circuit parameters of heterojunction bilayer copper phthalocyanine/perylene photovoltaic device on light intensity based on reverse bias characteristic

In order to study the dependency of organic photovoltaic device on light intensity, we investigate the current density-bias voltage characteristics of phthalocyanine/perylene thin film heterojunction photovoltaic device under illumination of various intensities. We use the standard one diode equivalent circuit to model the device and calculate the parameters included in the model. In calculating the parameters, we use the formula for short circuit current density and open circuit voltage and consider the reverse bias characteristics of the device, which provides two additional equations from only one additional fitting. Using this approach, we have four equations to determine five parameters. From our calculation, we find that the parameters depend on the intensity of light illumination that subsequently results on the decreasing of the performance of the device. The ideality factor and the photocurrent density is found to be linearly dependent on light intensity. The decreasing of parallel and series resistance when the light intensity increases is also found and, together with the linear-increasing of the value of ideality factor, are suspected to be the source of the decreasing of the device performance.