Influence of Cathode Work Functions on the Photovoltaic Properties of MEH-PPV: TiO<sub>2</sub> Bulk Heterojunction Solar Cell

Abstract

Bulk heterojunction solar cell has received significant attention over the past decade due to low cost power generation and the potential to develop a clean renewable energy source [. We investigated the effect of different type of metal cathodes on the power conversion efficiency of bulk heterojunction solar cell based on a blend of conjugated polymer poly [2-methoxy 5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) with titanium dioxide (TiO2). In this case of study, Aluminum (Al) and gold (Au) has been chosen as the metal cathode due to the difference of work function and their wide application in hybrid solar cell. We show that the choice of metal cathode plays a role in determining overall device efficiency through their impact on short-circuit current, open circuit voltage and fill factor due to the influence of work function. It is found that the device employing Al metal cathode which has low work function is showing a comparable performance to the Au metal electrode with fill factor of over 20 % and a power conversion efficiency of 3.3x10-3 %. Overall it is demonstrated that the matching between the work function of the cathode and photoactive layer MEH-PPV: TiO2 is the most important factor towards best bulk heterojunction solar cell performance.