Extremely Significant Steps Realized Toward Manufacturable Quantum Dot Solar Cell

The research program of Natcore Technology Inc. being conducted under a joint research agreement with Rice University has accomplished extremely significant steps toward realization of a manufacturable quantum dot solar cell. The work is being supervised by Prof. Andrew Barron, a Natcore co-founder.

Three key requirements must be met to make a quantum dot solar cell:

1. Create quantum dots of the proper size;
2. Create a uniform layer of those same quantum dots embedded in a thin film of silicon dioxide; and
3. Arrange the quantum dots such that the average inter-dot distance between any two of them is less than 10nm.

The scientists have successfully met all three requirements. The researchers successfully embedded 20nm-diameter germanium quantum dots (Ge QDs) inside smooth, round shells of silica (silicon dioxide); dispersed the coated quantum dots on a surface with a simple spraying technique; and coated the layer with a film of silicon dioxide using Natcore's liquid phase deposition (LPD) process. The coated quantum dots are represented by the chemical symbol Ge@SiO2.

Scanning electron microscopes and transmission electron microscope analysis of the films, coupled with a measurement of the photocurrent generated when the film was exposed to a light source, showed that very nearly 70% of the Ge@SiO2 quantum dots were within the 10nm maximum separation between nearest neighbors that is needed for high efficiency device operation. The resulting samples were one square centimeter in size.

With an applied voltage across the film thickness and illuminated by a laboratory white light operating at approximately one sun intensity, the film produced a current of over 6 milliamps. The 6ma current represents a threefold increase over the first attempts to make a QD layer device, as reported by Natcore in an earlier news release.

"We've been working towards this for a long time," says Dr. Dennis Flood, Natcore's co-founder and Chief Technology Officer. "It paves the way to a tandem solar cell using quantum dot material. We're preparing a provisional patent application."

Chuck Provini, Natcore's president and CEO, says, "This is a remarkable improvement in photo-generated current in the silica film. Prof. Barron's group has done an excellent job moving this from scientific research through proof of concept. Now the researchers at our Rochester R&D Center will focus on developing a working prototype."