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Organic and hybrid materials offer potential for low cost, large area, manufacturable solar-cells. Although there are multiple problems associated with these material systems, for example stability and lifetime, the primary issue at this point in time is that they simply have not offered operating efficiencies at an acceptable level. The Columbia EFRC is founded on the belief that improving photovoltaic efficiency for these systems requires fundamental and quantitative understanding of the energy flow through the system from the light absorption process to the power delivery process. The EFRC will focus on using the tools of nanotechnology and ultrafast science to achieve a deeper understanding of the fundamental efficiency limits of organic and hybrid solar cells at each step in the energy conversion cascade. We will apply this knowledge to the design and implementation of new, high efficiency solar-cell systems. Building from this understanding, we will explore material design for the creation of innovative and scalable architectures tailored to optimize charge extraction and transport. Furthermore, single junction organic and hybrid solar-cell systems are subject to the Shockley-Queisser (SQ) limitations for conversion efficiency. Many concepts for going beyond SQ have been proposed, but very little success has been reported so far for organic and hybrid systems. In particular the concept of carrier multiplication or multi-exciton generation (MEG) is attractive, but a deeper understanding of these processes is required to evaluate the potential for this concept. Thus our research program will examine extensively these concepts both theoretically and experimentally based on optimized nanomaterials created through cutting-edge synthesis capability.
In order to accomplish the goals of this program, we have organized our research into three basic research thrusts. The figure shows schematically the EFRC Thrust structure and how the elements within this research structure are interconnected. Fundamental knowledge, created through synergy of theory, measurement, and materials design across multiple disciplines, will iterate self-consistently, ultimately converging toward the precise electron- and molecule-scale control of matter that can enable development of highly efficient solar cells.
The research program of the EFRC centers around three multi-site, multi-disciplinary, and interlocking research thrusts. Each thrust represents an integrated effort incorporating theory, materials, and measurement.
Thrust 1 - Charge Generation: Excitation, Separation and Extraction
Thrust 2 - Charge Collection: Transport at the Nanoscale and Beyond
Thrust 3 - Carrier Multiplication: Beyond the Shockley-Queisser Limit
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