Area-scaling of Organic Solar Cells and Integrated Modules
- PDF / 226,109 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 36 Downloads / 242 Views
1212-S06-04-C07-04
Area-scaling of Organic Solar Cells and Integrated Modules
Seungkeun Choi, William J. Potscavage, Jr., and Bernard Kippelen1 Center for Organic Photonics and Electronics (COPE) and School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
ABSTRACT We report on the improved performance of large-area organic solar cells and modules by integrating metal grids directly with the indium tin oxide (ITO), thereby reducing the series resistance contribution from the ITO. Devices with different areas (0.1, 7, and 36.4 cm2) were prepared to study the area-dependency of the organic solar cells based on pentacene and C60 heterojunctions. Modules were prepared in which four individual cells (7 cm2) were connected in series and parallel. For the series connected modules, VOC scales linearly with the number of cells while parallel connected modules exhibited multiplied current density as expected.
INTRODUCTION Organic photovoltaic (OPV) devices have received great attention in recent years due to their promising potential for the development of large-area, low-cost, light-weight solar modules with highly flexible form factors [1]. Thanks to the improvements of active light-harvesting organic semiconductors [2] and new device architectures such as tandem cells, power conversion efficiencies beyond 5-6% have been demonstrated thus far [3]. For wide-spread use, OPV devices should be able to generate sufficient electric power either by increasing active area or connecting them together in a module without sacrificing power conversion efficiency. Modules are created either by connecting individual cells in series or parallel, thereby generating higher voltage or larger current, respectively. Although several results have been reported on OPV modules, they are often based on individual cells with a small area (less than few cm2) [4-6]. Benefits of large individual cells are apparent: Large cells can reduce manufacturing cost by minimizing interconnections and also maximize the packing factor. Recently, we reported that the finite conductance of indium-tin-oxide (ITO) was the major limiting factor when active area of OPV becomes large [7]. As area increases, power loss density through the electrodes also increases because current generally has to travel a longer distance through the resistive electrodes. Furthermore, high series resistance is known to reduce fill factor, photocurrent, and efficiency in organic photovoltaic cells [8-11]. Power loss density from the organic layers and interfaces are not affected by area because the current path length through these layers does not change with area. The primary contribution to power loss density comes from the transparent conductive electrode, usually ITO as the anode, because of its significantly higher resistivity compared to the opposite metal electrode. We demonstrated that the series 1
Author to whom correspondence should be addressed; electronic mail: [email protected]
resistance of a large-area OPV (7 cm2) ca
Data Loading...
