Influence of Cathode Work Functions on the Photovoltaic Properties of MEH-PPV: TiO₂ 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.

Graphene Modified TiO2 Composite Photocatalysts: Mechanism, Progress and Perspective

“…Graphene should be a competent material for this purpose compared with other carbon allotropes because of its highest electron mobility in theory. Moreover, photo-generated electrons in the conduction band of TiO 2 would spontaneously transport into graphene due to the more positive Fermi level of the former (work function is 4.6 eV for graphene and 4.2 eV for TiO 2 ) [ 14 , 115 , 116 ]. It is worth to note that the band bending at the interface of graphene and TiO 2 can be ignored due to their size (nano-scaled average size), which will be further discussed in Section 2.2.2 .…”