Time-dependent changes in absorption, emission, and/or photovoltage were measured for two chemical systems, organic electron donor-acceptor (EDA) complexes and inorganic metal oxides, in the picosecond and nanosecond time regimes. These changes were evaluated in terms of theories used to describe photoinduced charge separation. / Our investigations of several EDA complexes, which were composed of methyl- and halo-substituted benzenes and naphthalenes as donors (D) and tetracyanoethylene and chloranil acceptors (A), in solution involved ground-state absorption and steady-state emission analyses as well as time-dependent absorption and emission measurements. Photoexcitation into the charge-transfer bands of the EDA complexes resulted in the prompt formation of the contact radical ion pairs (CRIPs; $\rm D\sp{+\cdot},A\sp{-\cdot})$ whose lifetimes typically ranged $<$20 ps and 32 ns. / The interrelation of factors including reaction exoergicity, reorganization energies, electronic coupling between states, heavy-atom and isotopic substitution, local excited-state effects, and stoichiometry of the complex in the ground and excited states were elucidated with respect to the electron-transfer dynamics. The role of each of these factors in the photophysics of the EDA complex has been described in terms of theory for nonadiabatic electron transfer in the Marcus inverted region. / For the second type of chemical system, photovoltaic responses of polycrystalline wafers and oriented films of several metal oxides, including CuO, $\rm Cu\sb2O,\ Fe\sb3O\sb4,\ YBa\sb2Cu\sb3$O$\sb{7-x},$ and Bi$\sb2$Sr$\sb2$CaCu$\sb2$O$\sb{8+x}$, were measured in the absence of a transport current for a variety of excitation wavelengths, sample preparations, and environmental conditions. The largest responses were exhibited by YBa$\sb2$Cu$\sb3$O$\sb{7-x}$ wafers and films. For example, in response to irradiation with a 10-ns, 532-nm, 40-mJ laser pulse, polycrystalline wafers of YBa$\sb2$Cu$\sb3$O$\sb{7-x}$ exhibited room-temperature laser-induced transient photovoltages of $\sim$1 V maximum with a lifetime of $<$2.5 ns and an anisotropic dependence of the signal which scaled as the sine of the angle of incidence of the laser pulse and was nulled at normal incidence. The photovoltages were produced more efficiently with shorter wavelength light. In response to an $\sim$30-ps, 0.5-mJ, 532-nm laser pulse, the thin films of YBa$\sb2$Cu$\sb3$O$\sb{7-x}$ exhibited a peak voltage of $\sim$50 mV with a lifetime of $\sim$20 ns and a polarity which is reversed when the film is irradiated through the substrate rather than at the air/film interface. The mechanism for the laser-induced voltages in the films and wafers has yet to be established conclusively. / Source: Dissertation Abstracts International, Volume: 54-10, Section: B, page: 5123. / Major Professor: Edwin F. Hilinski. / Thesis (Ph.D.)--The Florida State University, 1993.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77024 |
| Contributors | Tate, Kerry Lee., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 416 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
Page generated in 0.0019 seconds