Fabrication of Large-Area Organic Photovoltaics Using a Draw-Bar Coating Technique
- PDF / 32,174,211 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 44 Downloads / 176 Views
Fabrication of Large-Area Organic Photovoltaics Using a Draw-Bar Coating Technique Cara J. Mulligan1, Nicolas C. Nicolaidis1,2, Ben Vaughan1,2, Xiaojing Zhou1, Warwick J. Belcher1 and Paul C. Dastoor1 1 2
Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia. CSIRO Energy Centre, Mayfield West, NSW 2304, Australia.
ABSTRACT Organic photovoltaic (OPV) devices were fabricated using a novel draw bar premetered coating technique, whereby a meniscus of fluid is dragged across a substrate to leave a trailing wet film. The results showed that coating thickness could be controlled by varying the coating speed, rod diameter, gap height, amount of solution injected, rod diameter, rod composition material and number of layers. Devices on PET with active areas of 10 cm2 and active layer thicknesses ranging from 35 to 475 nm were produced using the technique. Active layers of 160 nm were the optimum of thicknesses trialled, achieving typical best efficiencies around 0.4 %. Devices with films thinner than 90 nm did not function due to short-circuiting. The draw-bar coating method has the advantage of allowing controlled deposition of a wide range of film thicknesses with no solution wastage. INTRODUCTION Organic photovoltaic (OPV) devices for harvesting solar energy have the potential to be a widely adopted source of sustainable electricity for a range of applications. The devices can be solution processed; therefore inexpensive reel-to-reel printing and coating techniques are being investigated as a means of mass-producing OPV devices. There are a wide variety of conventional printing and coating techniques that have been applied to large area OPV fabrication, including slot die1,2, knife over edge1, screen printing1, gravure printing3,4,5 and spray coating6. Although some existing printing and coating techniques have successfully produced large area OPV, there is motivation to develop and explore novel techniques that may offer advantages such as reduced solution wastage, improved active layer thickness and patterning control, simpler design and more consistent substrate coverage leading to better yields. The novel coating technique examined in this paper was developed with the goal of incorporating these advantages, and this paper aims to explore the performance of the technique with respect to thickness control and consistency of the coated films. This work also demonstrates the successful production of large-area devices using the technique. EXPERIMENT The coating technique employed in this work has been termed “draw-bar coating”, and consists of a substrate being passed by a fixed cylindrical rod held several hundred microns from the surface. The coating fluid is introduced in the gap between the rod and substrate and the resulting meniscus is dragged along by the relative movement of the substrate and rod, depositing a trail of fluid. The amount of fluid in the meniscus can be held constant by
continuously trickling additional fluid onto the rod where it flows into the meniscus. Additi
