title: Low-Temperature Synthesis of a TiO2/Si Heterojunction.
abstract: The classical SiO2/Si interface, which is the basis of integrated circuit technology, is prepared by thermal oxidation followed by high temperature (>800 °C) annealing. Here we show that an interface synthesized between titanium dioxide (TiO2) and hydrogen-terminated silicon (H:Si) is a highly efficient solar cell heterojunction that can be prepared under typical laboratory conditions from a simple organometallic precursor. A thin film of TiO2 is grown on the surface of H:Si through a sequence of vapor deposition of titanium tetra(tert-butoxide) (1) and heating to 100 °C. The TiO2 film serves as a hole-blocking layer in a TiO2/Si heterojunction solar cell. Further heating to 250 °C and then treating with a dilute solution of 1 yields a hole surface recombination velocity of 16 cm/s, which is comparable to the best values reported for the classical SiO2/Si interface. The outstanding performance of this heterojunction is attributed to Si-O-Ti bonding at the TiO2/Si interface, which was probed by angle-resolved X-ray photoelectron spectroscopy. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) showed that Si-H bonds remain even after annealing at 250 °C. The ease and scalability of the synthetic route employed and the quality of the interface it provides suggest that this surface chemistry has the potential to enable fundamentally new, efficient silicon solar cell devices.
authors.affiliation: Department of Chemistry, ‡Department of Electrical Engineering, and §Princeton Institute for the Science and Technology of Materials, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: Girija
authors.initials: G
authors.lastname: Sahasrabudhe
authors.affiliation: Department of Materials Science & Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Sara M
authors.initials: SM
authors.lastname: Rupich
authors.forename: Janam
authors.initials: J
authors.lastname: Jhaveri
authors.forename: Alexander H
authors.initials: AH
authors.lastname: Berg
authors.forename: Ken A
authors.initials: KA
authors.lastname: Nagamatsu
authors.forename: Gabriel
authors.initials: G
authors.lastname: Man
authors.affiliation: Department of Materials Science & Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Yves J
authors.initials: YJ
authors.lastname: Chabal
authors.forename: Antoine
authors.initials: A
authors.lastname: Kahn
authors.forename: Sigurd
authors.initials: S
authors.lastname: Wagner
authors.forename: James C
authors.initials: JC
authors.lastname: Sturm
authors.affiliation: Department of Chemistry, ‡Department of Electrical Engineering, and §Princeton Institute for the Science and Technology of Materials, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Schwartz