Paper TF1-ThA2
Atomic Layer Deposition of Alternative Energy Materials

Thursday, October 18, 2007, 2:20 pm, Room 602/603

Atomic layer deposition (ALD) is a method for depositing thin films of semiconducting, insulating and metallic materials using an alternating series of self-limiting reactions between gas phase precursors and the substrate. Over the past several years, ALD has grown steeply in popularity as a choice for the semiconductor industry. However, ALD’s real potential for impact may lie in even more novel applications, including those in alternative energy. This presentation will describe our recent studies using ALD for the deposition of thin films for both fuel cell and solar cell applications. For solid oxide fuel cells (SOFCs), we have explored ALD for the fabrication of an ultra-thin Pt film for use as the electrocatalyst, and a Pt mesh structure for a current collector, as a means of improving catalyst performance at lower temperatures. Pt ALD was carried out using (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe₃) and O₂ as precursors and N₂ as a carrier and purging gas. Ex situ analysis of the as-deposited Pt films shows that the platinum film is of excellent uniformity, with no measurable impurities and low electrical resistivity. In addition to the blanket deposition of platinum, we have used the technique of area selective ALD, by combining the methods of ALD and microcontact printing, for fabrication of spatially patterned Pt, to be used as a current collector grid for SOFCs. Working SOFC fuel cells were fabricated with ALD-deposited Pt, and their performance was characterized by a potentiostat-impedance system. The results show that comparable initial performance can be achieved with ALD deposited Pt anodes compared to the RF sputtered Pt anodes with only one-eighth the platinum loading required in the ALD film. For the photovoltaic application, we will describe a vertical nanostructured geometry in which the carrier diffusion length is decoupled from solar radiation absorption, enabling high efficiency cells to be fabricated inexpensively out of low quality materials. We will describe how ALD and other deposition methods can be used to deposit thin films of photovoltaic materials to make nanocomposite solar cells.