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Photon conversion embodies a range of promising possibilities in pushing the theoretical Shockley–Queisser efficiency model of classical solar cells. Luminescent down-conversion, despite its potential, is held back in practical applications due to the difficulty of proper characterization in no small part because of concurrent luminescent downshifting events. Recent advances have demonstrated the opportunity provided by photon correlation measurement for down-conversion characterization. In this methodological work, we present a general method based on Bayesian probabilities for deriving auto-correlation functions analytically. This method is then applied to the five down-conversion mechanisms reported in the literature and successfully tested against numerical simulations. We show that the zero delay auto-correlation function can be the most direct way to demonstrate down-conversion and assess its efficiency. Our analysis offers additional useful tools for the design of characterization experiments and emphasizes some universal behavior valid for all reported conversion mechanisms. [ABSTRACT FROM AUTHOR]

The nature of the water in hydrated polymer electrolyte membranes (PEMs) is not the same as that of bulk water and affects the rate of diffusion of protons in the material. The traditional methods used in the study of the phenomenon of dielectric saturation assume the presence of a homogeneous or slowly varying external field, conditions that are hard appropriate for (PEMs).

A detailed rheological investigation of a lower critical solution temperature (LCST) blend of deuterated polystyrene-38K/PVME-23K near the critical region is presented. The phase behavior of the blend in the transitional regime was studied by the viscoelastic response of the system during dynamic temperature sweep experiments.

A theoretical study is conducted on the bridge mediated two-electron transfer (TET) in a donor-acceptor (D-A) complex. A type bridge is considered where the intersite coupling in the bridge becomes so large that the TET proceeds along delocalized bridges states but against the background of fast vibrational transitions within and between the states.

Density functional theory (DFT) used the B3LYP method to study the vibrational modes of double six-member ring (D6R) clusters with general composition (M(super n+))x/nH12Si(sub 12-x)Al(sub x)O18 (where x=0.2 and M=H(super +), Na(super +), K(super +), Ca(super 2+), Li(super 2+)).

A study was conducted on the electrodeposition of ZnSe films from dimethyl sulfoxide solutions with a special focus on epitaxial growth. The influence of experimental parameters such as the nature of the substrate, temperature, and hydrodynamic conditions were examined.

A study on Cu(In,Ga)Se2-based polycrystalline thin film solar cells presents a comprehensive picture of chemical oxygenation effects and their consequences for the electronic properties of such Cu(In,Ga)Se2-based solar cells. Two distinct effects of air annealing of the absorber surface were observed: first, oxygenation leads to passivation of surface defects both at the grain boundaries and at the free surface of the Cu(In,Ga)Se2 film. Second, air annealing at 200 degrees C leads to a decrease in CU concentration at the absorber surface, which ultimately results in a decrease of space charge density within the absorber.

Being at the origin of an ohmic contact, the MoSe2 interfacial layer at the Mo/Cu(In,Ga)Se2 interface in CIGS (Cu(In,Ga)Se2 and related compounds) based solar cells has allowed for very high lightto- electricity conversion efficiencies up to 22.3%. This article gives new insights into the formation and the structural properties of this interfacial layer. Different selenization-steps of a Mo covered glass substrate prior to the CIGS deposition by co-evaporation led to MoSe2 interfacial layers with varying thickness and orientation, as observed by x-ray diffraction and atomic resolution transmission electron microscopy. A novel model based on the anisotropy of the Se diffusion coefficient in MoSe2 is proposed to explain the results. While the series resistance of finished CIGS solar cells is found to correlate with the MoSe2 orientation, the adhesion forces between the CIGS absorber layer and the Mo substrate stay constant. Their counter-intuitive non-correlation with the configuration of the MoSe2 interfacial layer is discussed and related to work from the literature. [ABSTRACT FROM AUTHOR]

Upconverted emission from erbium ions in fluoride materials (glass and disordered crystal of the system CaF2-YF3) are observed in a wide spectral range (from the visible to the near infrared) under infrared excitation at 1.54 μm. In both cases, the upconverted emission in the near infrared (~1 μm) dominates the spectrum. Absolute UC efficiency defined as the ratio between the UC luminescence power and the absorbed pump power has been experimentally measured. The NIR (~1 μm) luminescence energy yield for the glass and the disordered crystal varies from 2.4 to 11.5% for the glass and from 7.7 to 16% for the crystal for an infrared excitation power density ranging from 2 W/cm2 to 100 W/cm2. This is of a particular interest for their use as upconverter to improve the c-Si cells quantum efficiency since the energy of the excitation lies below the c-Si absorption edge (1.12 eV at 300 K) and is well located compared to the AM1.5G solar spectrum, outside of the absorption lines due to different atmospheric gases. Furthermore, the most efficient upconverted emission recorded in the investigated materials occurs at an energy just above the gap. A current generated in a bifacial c- Si solar cell is observed when the Er3+ doped material (1.55 mA and 2.15 mA for the glass and the crystal respectively), placed at the rear face of the cell, is excited at 1.54 μm. The current dependence as a function of the sub-bandgap excitation power has been measured and modelled. Finally the EQE of the complete device is deduced from the measured short-circuit current and the incident photon flux on the cell. An increase of the cell quantum efficiency of 2.4% and 1.7% is obtained at 1.54 μm with adding the glass and the crystal respectively at the rear face of the c-Si cell. The results are compared to those already obtained with Er: NaYF4 known as the most efficient upconverter.

We analyzed the luminescence signal under electrical bias (Lum-V) for several Cu(In,Ga)Se2 solar cells having different absorber growth processes and different buffer layers such as CdS and ZnS. A numerical model is developed taking into account optical and electrical properties of the complete heterostructures. It appears that the absorber-buffer interface has a crucial role in explaining the different behaviors. Our interpretation is based on the quasi Fermi level splitting (QFL) linked to both the applied voltage and the luminescence intensity. Lum-V experiments and its dependence on illumination intensity are discussed and could be used to access transport properties when looking at the depth variation of the QFL and offer a classification of the possible cases. [ABSTRACT FROM AUTHOR]

III-V/Si heterostructures are currently investigated for silicon photonics and solar energy conversion. In particular, dilute nitride alloy GaAsPN grown on a GaP/Si platform exhibits lattice match with Si and an optimal band gap configuration for tandem solar cell devices. However, monolithic "coherent" growth of the GaP thin layer on Si suffers from the nucleation of extended structural defects, which can hamper device operation as well as the GaP/Si interface level and through their propagation inside the overall heterostructure. However, the effect of such structural defects on optical and transport properties is actually not well understood in details. In this letter, we investigate the anti phase domains defect (also called inversion domains) by means of ab initio calculations giving insights into the alteration of optical and transport properties of GaP due to the defective GaP/Si interface. [ABSTRACT FROM AUTHOR]