High Pressure Effects on the Band Structure and Dye-Sensitized Photospectra of Semiconductors

87 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983.The effect of high pressure (to 10 kilobars) on the band edge structure of n-TiO(,2), n-CdS, and n-CdSe has been investigated using an electrochemical technique. This study presents a novel method of measuring the energy of the band positions. It was found that the 3 meV/kbar increase in the band-gap (E(,g)) of TiO(,2) is due solely to a 3 meV/kbar increase in the conduction band edge energy (E(,C)), with the valence band edge (E(,V)) stationary. For CdS, the 5.1 meV/kbar increase in E(,g) is due to the 9.5-11.5 meV/kbar increase in E(,C) and the (calculated) 4.5-6.5 meV/kbar increase in E(,V). For CdSe, both E(,C) and E(,V) are lowered, with the more rapid lowering of E(,V) accounting for the increase of E(,g) with pressure. Comparisons with the literature are made.In addition, the effect of high pressure on the dye-sensitized photocurrent spectrum of n-TiO(,2) was investigated. The dye was a complex of ruthenium, bis(2,2'-bipyridine)(2,2'-bipyridine-4,4'-dicarboxylate) ruthenium (II), chemically attached to the TiO(,2) surface. It was found that the shift of the absorption peaks of the dye dissolved in solution was identical to the shift of the peaks resolved in the photocurrent spectrum, indicating a sensitization process involving initial excitation to a dye excited state, rather than excitation directly into the conduction band, as has been previously suggested.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD