Events

“Plastic” Solar Cells: Self-Assembly of Bulk Heterojunction Nano-Materials by Spontaneous Phase Separation

October 20, 2009 at 3pm/36-428

Alan Heeger
Department of Chemistry, University of California, Santa Barbara

abstract:
Solar cells — Power from the Sun — can provide and must provide — a significant contribution to our future energy needs. The challenge is clear; we must create the scientific foundation and the technology to enable fabrication of high efficiency solar cells at low cost. I will describe the discovery of ultrafast photoinduced electron transfer as the scientific foundation for the creation of a technology for low cost “plastic” solar cells. This initial charge separation occurs at a time scale two orders of magnitude faster than the first step in photo-synthesis in green plants. Charge collection at the electrodes is accomplished through self-assembly of bulk heterojunction (BHJ) nano-materials by spontaneous phase separation.

Recent results include the achievement of 6% power conversion efficiency and the demonstration of quantum efficiencies approaching 100%: Each photon absorbed leads to a (positive and negative) pair of mobile charge carriers, and all the photo-generated charge carriers are collected at the electrodes. Higher efficiencies will come from improved harvesting of the photons from the solar spectrum using new semiconducting polymers designed and synthesized for use in “plastic” solar cells.
We see a clear technology pathway to high efficiency “plastic” solar cells with lifetimes sufficient for a wide range of applications including portable electronics, semi-transparent solar cells for windows in homes and buildings, and rooftop installation. I will discuss lifetime issues and progress toward manufacturing plastic solar cells by printing/coating technology. I will demonstrate that the dream of low cost plastic solar cells is becoming reality.

bio:
Widely known for his pioneering research in and the co-founding of the field of semiconducting and metallic polymers, Professor Heeger is also the recipient of numerous awards, including the Nobel Prize in Chemistry (2000), the Oliver E. Buckley Prize for Condensed Matter Physics, the Balzan Prize for the Science of New Materials, the Eni Italgas Prize for Energy and the Environment, the President’s Medal for Distinguished Achievement from the University of Pennsylvania, the Chancellor’s Medal from the University of California, Santa Barbara, and honorary doctorates from more than a dozen universities in the United States, Europe and Asia. He is a member of the National Academy of Science (USA), the National Academy of Engineering (USA) and a foreign member of the Korean Academy of Science. Prof. Heeger founded UNIAX Corporation in 1990; UNIAX was acquired by DuPont in 2000. Prof. Heeger is Chairman and Co-founder of CBrite Inc. in Santa Barbara.