Integrating metalloporphycenes into p-type NiO-based dye-sensitized solar cells

In the current work, we have explored a novel synthetic route towards metalated porphycenes and their use in p-type NiO-based dye-sensitized solar cells. Particular emphasis is placed on the influence that the relative positioning of the anchoring group exerts on the DSSC performance

Multidimensional signals and analytic flexibility: Estimating degrees of freedom in human speech analyses

Recent empirical studies have highlighted the large degree of analytic flexibility in data analysis which can lead to substantially different conclusions based on the same data set. Thus, researchers have expressed their concerns that these researcher degrees of freedom might facilitate bias and can lead to claims that do not stand the test of time. Even greater flexibility is to be expected in fields in which the primary data lend themselves to a variety of possible operationalizations. The multidimensional, temporally extended nature of speech constitutes an ideal testing ground for assessing the variability in analytic approaches, which derives not only from aspects of statistical modeling, but also from decisions regarding the quantification of the measured behavior. In the present study, we gave the same speech production data set to 46 teams of researchers and asked them to answer the same research question, resulting insubstantial variability in reported effect sizes and their interpretation. Using Bayesian meta-analytic tools, we further find little to no evidence that the observed variability can be explained by analysts’ prior beliefs, expertise or the perceived quality of their analyses. In light of this idiosyncratic variability, we recommend that researchers more transparently share details of their analysis, strengthen the link between theoretical construct and quantitative system and calibrate their (un)certainty in their conclusions

Neuentwickelte Pentacene Derivate für die Singulett Fission Forschung: Theorie, Fotophysik und Anwendung in Farbstoff- Sensibilisierten Solar Zellen

As technology evolves, the production of energy is moving towards more efficient and less harmful methodologies. Using solar energy conversion architectures, which take into account the lessons learned in 50 years of solar energy research, a new set of organic-based sensitizers in conjunction with highly customizable semiconductor materials is being developed. The fields of singlet fission and dye-sensitized solar cells combined means a novel field for solar energy conversion. As such, singlet fission represents a novel photophysical process with high yield of produced charges and the latter is a specific architecture based on the electrochemical potentials of the components herein. In order to understand the theory behind the high quantum yield, several theoretical and computational methodologies were applied. To corroborate energies, electrochemical potentials and state dynamics several spectroscopic techniques such as steady state absorption and emission, as well as transient absorption spectroscopy were applied. Lastly, the design, construction and implementation of solar cells architectures were undertaken. The thesis herein develops and summarizes a set of investigations with the aim of applying advanced techniques and learn about novel photophysical concepts by implementing those concepts into state-of-the-art prototypes for the solar industry. This looking to demonstrate a proof of concept and give a rational explanation of the process. After a short introduction and theoretical considerations to properly understand the presented photophysical, and experimental concepts, the investigations presented herein are divided in three main parts. The first part of the thesis aims to optimize the electron transfer process between the interlayers in dye-sensitized solar cells by means of implementing carbon allotropes. As well, to characterize important factors and obtain data via current-voltage measurements, electrochemical impedance spectroscopy, and photon-to-current spectra. From the latter follows several investigations with the aim of understanding singlet fission from a solution and pure photophysical stand point. That is, understanding the intrinsic dynamics and necessary energetic requirements to obtain the highest quantum yield via optical spectroscopy and computational methods. Looking into several novel pentacene derivatives to unravel effects on singlet excited states and triplet excited states, as well as the singlet fission mechanism. The last section, is the implementation of the pentacene-dyes into a dye-sensitized solar cell architecture. The photophysical characterization of the singlet fission dyes in the solid state and coupled to a semiconductor is novel and paves the road towards better singlet fission dyes, which can produce quantum yields close to 200% and transfer most of their yield in charges to the semiconductor, hence providing close to double of the current in the device

Geometry and electronic structure of neutral and charged B21 clusters

We use random searches, basin hopping and simulated annealing techniques to obtain low energy isomers of the B21 cluster. Our search shows that planar structures dominate the low energy isomers of B21 for the neutral as well as singly positively and negatively charged states continuing the trend seen for smaller clusters. The ring-like structures previously reported as global minima for the B20 and B21 are about 1 eV higher than the most stable planar isomer. The quantum chemical calculations using the second order Moller–Plasset perturbation theory agree with the DFT predictions

Perylene-Monoimides: Singlet Fission Down-Conversion Competes with Up-Conversion by Geminate Triplet-Triplet Recombination

Triplet-excited-state energies of perylene-monoimides (PMIs) lie in the range 1.12 eV ± 2 meV when compared to singlet-excited-state energies of about 2.39 eV ± 2 meV; therefore, the corresponding naphthalene-linked PMI-Dimer was investigated as a novel singlet-fission (SF) material. Ultrafast transient absorption measurements demonstrated the (S1S0)-to-1(T1T1) transformation and the involvement of a mediating step in the overall 1(T1T1) formation. The intermediate is a charge-transfer state that links the initial (S1S0) with the final 1(T1T1), and imposes charge-transfer character on both, which are thus denoted (S1S0)CT and 1(T1T1)CT. At room temperature, the decorrelation and stability of 1(T1T1)CT is affected by the geminate triplet-triplet recombination (G-TTR) of the two triplets. Independent confirmation for G-TTR to afford up-converted (S1S0)UC in fsTA and nsTA measurements with PMI-Dimer, came from probing PMI-Monomer (T1)s in triplet-triplet annihilation up-conversion (TTA-UC). The G-TTR channel, active in the PMI-Dimer at room temperature, is suppressed by working at either low temperatures (∼140 K) or in polar solvents (benzonitrile): Both scenarios assist in stabilizing (T1T1)CT. As a consequence, the triplet quantum yields are 4.2% and 14.9% at room temperature and 140 K, respectively, in 2-methyltetrahydrofuran

CEO Tenure and Entrepreneurial Orientation Within Family and Nonfamily Firms

The current research investigates how entrepreneurial orientation changes during a chief executive officer (CEO)\u27s tenure in family and nonfamily firms. Based on secondary data collected from 210 firms representing five industries, the results show an inverse U-shaped relationship between CEO tenure and entrepreneurial orientation, consistent with the executive life cycle literature. Moreover, in family firms the shape of the inverse U is less pronounced and the level of entrepreneurial orientation peaks considerably later in the CEO\u27s tenure when compared with nonfamily firms