12.3.1 Metalloporphyrin Excited State Structural Dynamics (Homogeneous Electron/Energy Transfer) Metalloporphyrins and derivatives play many important roles in solar energy conversion as light harvesting antennae and electron donors in natural photosynthesis, dye sensitizers in solar cells, photocatalysts for redox reactions, and so on.75 79 Their intense absorption from the я-я* transitions in the solar spectrum enables […]

XTA is analogous to the optical transient absorption spectroscopy (OTA) (see the overview in Chapter 5); a laser pump pulse triggers photoexcitation or a photochemical reaction, mimicking light absorption of solar photons and an X-ray pulse (instead of the second laser pulse in OTA) probes electronic and geometric structures of the samples as the result […]

12.2.1 Development of X-ray Transient Absorption Spectroscopy 12.2.1.1 X-ray Absorption Spectroscopy X-ray absorption spectroscopy (XAS), including X-ray absorption near edge structure (XANES) and X-ray absorption fine structure (XAFS), is based on resonant absorption processes resulting from electronic transitions from core levels to vacant orbitals and to the continuum, respectively (Figure 12.1).15 18 XANES measures dipole-mediated […]

LIN X. CHEN Chemical Sciences and Engineering Division, Argonne National Laboratory, Building 200, 9700 South Cass Avenue, Argonne, Illinois 60439; Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA Email: lchen@anl. gov; l-chen@northwestern. edu 12.1 Introduction The amount of energy from sunlight reaching the earth in one hour equals the total amount […]

Organic semiconductors have emerged as potential candidates for use in low – cost electronic devices, including solar cells.135 They are commonly divided into two classes: small molecules that are typically deposited as crystalline material by evaporation and semiconducting organic polymers that are processed in solution. Optically excited excitons in organic semiconductors possess high binding energies […]

Electronically coupled QD superlattices have been also considered for novel PV applications. Indeed, the best reported photocurrents on QD-based solar cells have been obtained for Schottky cells made of QD solids.129 Also, QD super­lattices have been employed as building blocks for tandem QD-based PV de – vices.62 For all these reasons, it is hence of […]

The QD sensitization of mesoporous oxides (on QD sensitized solar cells, QDSSCs) has been proposed as an alternative for dye sensitization with dyes.122 The reason is the increased absorption cross section for QDs and the possibility of tuning the QD band gap by varying the size (allowing for readily matching the solar spectrum). However, these […]

In 1991 O’Reagan and Gratzel introduced the dye sensitized solar cell (DSSC)5 as a low cost alternative PV concept to conventional p-n junction based solar cells. In DSSCs, a high surface area, dye-sensitized mesoporous oxide film (usually TiO2) acts as anode. After photon absorption by the dye molecules, electrons are injected from the excited dye […]