Quantum Confinement Solar Cell
In this project, our group is studying the application of atomic layer deposition (ALD) to fabricate nanoscale photovoltaic devices. The focus is on the incorporation of quantum wells and dots into the active area of the device to improve efficiency and study the underlying physics of charge extraction in these materials. ALD is used to fabricate the quantum-confined structures, as well as thin barrier layers and transparent top electrodes. The ability of ALD to conformally coat high- aspect-ratio structures with materials with sub-nm precision is a unique and powerful ability that allows for the fabrication of several novel device architectures.
(left) W. Lee, N. P. Dasgupta, H. J. Jung, J.-R. Lee, R. Sinclair and F. B. Prinz, “Scanning tunneling
spectroscopy of lead sulfide quantum wells fabricated by atomic layer deposition”, Nanotechnology, 21,
(right) N. P. Dasgupta, H. J. Jung, O. Trejo, M. T. McDowell, A. Hryciw, M. Brongersma, R. Sinclair and F. B. Prinz, “Atomic Layer Deposition of Lead Sulfide Quantum Dots on Nanowire Surfaces”, Nano Lett., 11(3), 934-940 (2011).
Characterization is performed using a variety of techniques including transmission electron microscopy (TEM), scanning tunneling microscopy (STM), x-ray techniques, and optoelectronic device measurements. Solar cells are fabricated using MEMS processing in the Stanford Nanofabrication Facility, and a customized ALD reactor in the nanoscale prototyping laboratory. Quantum chemical simulations are also performed in order to model the energetics of ALD reactions and the electronic structure of the semiconductor materials that are used.