James Yardley

Louis Brus

Tony Heinz

EFRC Managing Director: James Yardley
EFRC Scientific Directors: Louis Brus and Tony Heinz

N. J. Tremblay, A. A. Gorodetsky, M. Cox, T. Schiros, B. Kim, A. Sattler, W. So, Y. Itoh, M. F. Toney, A. P. Ramirez, I. Kymissis, M. Steigerwald, and C. Nuckolls, submitted.

The Columbia EFRC is creating technology which will redefine photovoltaic efficiency in organic and hybrid systems through fundamental understanding and molecule-scale control of the key steps in the photovoltaic process.

The EFRC focuses its expertise in chemical synthesis, fabrication, manipulation, and characterization to systematically develop understanding of the primary photovoltaic processes in organic and hybrid materials. In addition, it seeks to develop and quantitatively investigate nanostructured materials with potential for extracting multiple electrical charges from a single absorption event, thus establishing a scientific basis for moving the efficiency of these solar cell devices well beyond the Shockley-Queisser efficiency limit.

The Columbia EFRC is a collaboration between University of Arkansas (Prof. Xiaogang Peng), University of Texas (Prof. Xiaoyang Zhu), Purdue University (Prof. Ashraful Alam), and the Brookhaven National Laboratory.

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 1Thrust 1 is dedicated to understanding the charge generation process: excitation, separation and extraction of charge carriers. In this thrust we are developing a set of new, chemically well-characterized, nanoscale materials including asymmetric quantum dots and novel “molecular clusters.” We are quantifying the dynamics and effectiveness of photophysical processes, using modern tools including ultrafast and single molecule spectroscopies. We are also building a theoretical framework to model kinetic processes for charge transport, with input from atomic scale calculation of local bonding, structure and electronic states. We are measuring the effectiveness of charge transport across interfaces using a variety of techniques including photoemission.

Thrust 2Thrust 2 examines “Charge Collection: Transport at the Nanoscale and Beyond.” In this thrust we are building new materials suitable for studying the fundamental physics in bulk heterojunction solar cell devices, including chemically-tailored semiconductor materials and ordered interfaces. We are developing theoretical models for exciton dissociation, diffusion, and separation in these structures. We are supporting these models with nanofabricated devices using both top-down and bottom-up approaches which allow us to directly measure charge transport.

Thrust 3Thrust 3 explores “Carrier Multiplication: Beyond the Shockley-Queisser Limit.” Our program seeks to identify experimental signatures for multi-exciton generation (MEG) and related singlet fission processes. We are developing structures and materials for optimal carrier multiplication schemes through systematic exploration of quantum dot and carbon-based systems such as graphene nanoribbons or carbon nanotubes. Finally, this thrust is establishing quantitative and predictive theory for carrier multiplication concepts.