Study of the open circuit voltage dependence on incident light intensity of planar heterojunction organic solar cell

Abstract

Organic photovoltaic is an emerging technology employing organic molecules as absorbers has gained tremendous attention in the past two decades due to its potential utilization as a renewable energy source. Contrary to conventional solar cells, excitons are formed under illumination which diffuse towards the heterojunction interface for dissociation into the photo charge-carriers. Heterojunction in the organic photovoltaic devices are formed either by stacking the layers of donor and acceptor molecules or by blending the both. Due to weak van-der Waals interaction between the molecules, intermixed states, in addition to the pure states of donor and acceptor molecules, are formed at the heterojunction interface which affects the electronic process and the power conversion efficiency. Significant efforts have been made to understand the photovoltaic process particularly in the bulk heterojunction solar cells however, least efforts have been devoted to investigate the governing mechanisms in the planner heterojunction solar cells. The motive of this study is to characterize the planar heterojunction solar cells based on the Copper Phthalocyanine (CuPc) and Fullerene (C60) molecules under light illumination. The devices were fabricated under controlled condition in the normal device configuration, ITO (150 nm) |PEDOT:PSS(50 nm)|CuPc(20 nm)|C60(40 nm)|BCP(10 nm)| Ag(80 nm), and characterized performing the light intensity dependent measurement in the wide illumination range. The solar cell parameters such as open circuit voltage, short circuit current and the power conversion efficiency have been discussed as a function of illumination intensity in the wider illumination range.