International Seminar on Science and Technology, ISSTEC 2009, Yogyakarta, Indonesia

A Proof of Dependency of Organic Photovoltaic Device Diode Ideality Factor on Light Intensity Using Linear Approximation near Break-down Voltage Method

Sholihun, Kuwat Triyana, Timothy Siahaan and Budi Prabowo Soewondo

Physics Department, Faculty of Mathematics and Natural Sciences, Gadjah Mada University
Sekip Utara BLS 21, Yogyakarta 55281, Indonesia

e-mail: triyana@ugm.ac.id, lion_avs@yahoo.com

Abstract. In determining photovoltaic device internal parameters, we have compared the result of two assumptions about diode ideality factors (n). First assumption is that n is a generic property of the device, which is independent on light intensity, so that the value of the parameter determined from the data obtained on darkness (without illumination). Second assumption is that n is an intensity-dependent parameter. The calculation of internal parameters is done based on the reverse bias characteristic and used the assumption that there is a linear profile near the breakdown voltage on the current-voltage (J-V) curve. We called this method as Linear Approximation Near Breakdown Voltage (LANBV) method from now on. To find out whether n is independent or dependent on light intensity, we have done curve fitting between the J-V curves obtained from experiment with the curve obtained from each assumption. For the first assumption there is significance deviation between the curves obtained from both conditions. Surprisingly, the second assumption gives a very good fitting to the current density-bias voltage curve in that we cannot distinguish the curve from our approximation with the curve from the experimental data. Finally, we conclude that there is dependency between organic photovoltaic device diode ideality factor and intensity of illumination.

Keywords : photovoltaic device, reverse bias characteristics, LANBV method