Atomic Layer Deposition of High Performance Ultrathin TiO2 Blocking Layers for Dye-Sensitized Solar Cells



Invited for this month′s cover is the group of Gregory Parsons at North Carolina State University. The image shows one cycle of TiO2 atomic layer deposition (ALD), in which the sequential dosing and purging of TiCl4 and H2O forms ultrathin and conformal TiO2 films on rough FTO glass. Pinhole-free ALD TiO2 forms a blocking layer to impede electron–hole recombination at the FTO/electrolyte interface in dye-sensitized solar cells. The ALD process allows discrete tuning of the blocking-layer thickness to maximize performance improvement. Read the full text of the article at 10.1002/cssc.201300067

What is the most significant result of this study?

12We find that a 5 nm thick ALD blocking layer is sufficient to suppress electron–hole recombination in dye-sensitized solar cells. The best-performing ALD blocking layer is thinner than layers formed by other thin film deposition methods, allowing good charge transport into the FTO to be maintained.

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Do Han Kim  Mariah Woodroof

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Kyoungmi Lee  Prof. Gregory N. Parsons

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Department of Chemical and Biomolecular Engineering North Carolina State University Raleigh, NC 27695 (USA) Fax: (+1) 919-515-3465 E-mail:

What time-consuming dead-ends delayed the results before this breakthrough?

It was difficult to obtain reliable and consistent results in each thickness. We had to standardize fabrication methods and then strictly follow the method for every sample preparation. Each device result reported represents the average of three devices made under the same conditions. We know, therefore, that the reported trends are readily reproducible.

What future opportunities do you see?

ALD blocking layers demonstrate how vapor-phase nanoscale material engineering can be important in an electrochemical system. We see significant new opportunities for ALD materials and processes in other photoelectrochemical and photoelectro-synthesis cell structures.


The authors acknowledge support from the U.S. Department of Energy Project (8NT0001925).

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