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Light-induced metastabilities of Cu(In,Ga)Se2 (CIGS)-based thin film solar cells have been extensively researched for many years. It is commonly observed that junction capacitance and p-doping level in CIGS absorbers increase considerably after light soaking (LS). In this work, we focus on the LS behaviors of cells with different minority carrier lifetimes (τn). Experiments show that high efficiency cells with long τn lose open circuit voltage (Voc) and fill factor (FF) upon LS, whereas low efficiency cells with short τn lose less or even gain Voc and FF. The sodium content measured with glow discharge optical emission spectroscopy (GD-OES) increases in the region close to the CdS/CIGS interface with LS and may contribute to the observed LS behaviors. The change in electrical parameters is explained with simulations, which relate the Voc and FF changes to a reduced recombination rate in the space charge region due to the light-induced doping increase. The simulations also suggest that cells with higher n-doping in the CdS are less sensitive to changes in interface recombination rate and doping of CIGS, which agrees with the hypothesis that the CdS buffer deposition is important for the LS behavior.

Dispersed fluorescence spectroscopy and photoelectron spectroscopy have been employed to study vibronic coupling in excited neutral and ionic states of carbon dioxide. The dispersed fluorescence excitation spectra of the CO 2 + B ˜ ( 0 0 1 ) 2 Σ g + → X ˜ ( 0 0 1 ) 2 Π u and the B ˜ ( 0 0 2 ) 2 Σ u + → X ˜ ( 0 0 2 ) 2 Π g transitions have revealed new structure. Some of this structure can be assigned to n sσ g or n d Rydberg series converging onto the CO 2 + C ˜ ( 0 0 1 ) 2 Σ u + threshold or to an n p Rydberg series converging onto the CO 2 + C ˜ ( 0 0 2 ) 2 Σ g + threshold. Autoionisation from Rydberg states belonging to these series results in the formation of ions with one or two quanta of the asymmetric stretching mode being excited. The HeI excited photoelectron spectra of the CO 2 + B ˜ 2 Σ u + and C ˜ 2 Σ g + states reveal extensive and complex vibrational structure. Transitions involving the non-totally symmetric bending and asymmetric stretching modes have been observed. The occurrence of these normally forbidden transitions is attributed to vibronic interactions.

Insertion of H+, Li+, Na+ and K+ into thin films prepared from silicotungstic acid - a photoelectron spectroscopy study

Photoelectron spectroscopy is used to measure the electronic d. of states in the band gap region of a nanostructured TiO2 film. Such nanostructured films are used in dye-sensitized solar cells, and a plain TiO2 film as well as a dye-sensitized film were examd. To simulate the electrolyte effect on the energy levels at the oxide/dye/electrolyte interface in a solar cell, the d. of states in the band gap region for an electrochem. prepd. TiO2 film inserted with Li+ was measured. The distribution and chem. nature of electron trap states in the band gap and the energy matching between the LUMO level of the adsorbed dye, cis-bis(4,4'-dicarboxy-2,2'-bipyridine)-bis(isothiocyanato)ruthenium(II), and the TiO2 conduction band edge are discussed.

The charge transport in nanoporous ZnO was studied by laser flash induced photocurrent transients. The results are discussed using a diffusion model and compared with previous results on TiO2. The charge transport was highly dependent on the potential giving apparent diffusion coeffs. for the electron ranging from 1×10-4 to 1×10-6 cm2/s with an applied bias of +100 and +300 mV vs. Ag/AgCl in ethanol, resp. The electrolyte was 0.5 M LiClO4 in ethanol. The potential dependence was much more pronounced for ZnO than for TiO2. The charge transport was also dependent on the electrolyte giving a linear dependence between the cond. of the electrolyte and the apparent electronic diffusion coeff. The dependence of the light intensity was also studied. Intensity-dependent losses were obsd.

The electronic structure of cis-bis(4,4'-dicarboxy-2,2'-bipyridine)bis(isothiocyanato)ruthenium(II) and of its ligand 2,2'-bipyridine-4,4'-dicarboxylic acid was studied with electron spectroscopy. Valence level spectra were studied with respect to photoelectron angular distributions and photon energy dependence. The exptl. information coupled with semi-empirical INDO/S calcns. provides a mapping of the orbital parentage of the dye complex and its ligands. The energy levels of the dye complex in the context of a sensitized semiconductor (nanostructured TiO2) surface are related to the bands of the semiconductor.

The effect of oxygen in nanocryst. colloidal TiO2 film photoelectrodes were studied by optically induced photocurrent transient measurements. O2 played an important role in the recombination of electrons and holes. Some effects esp. assocd. with the nanoporous morphol. of these photoelectrodes are discussed.

Verification of High Efficiencies for the Gratzel Cell : A 7% Efficient Solar Cell Based on Dye-Sensitized Colloidal TiO2 Films.