1,100 research outputs found
Kosciusko [music] /
No full textFor voice and piano.; Cover title.; "Introduced & sung by Miss Nella Webb."; Cover carries portraits of Nella Webb (by Rudolph Buchner), Charles Vaude and Moritz Lutzen.; Words printed as text on p. [4].; "During Moritz Lutzen's visit to Australia he offered a prize for the best lyric, by an Australian author to be set to music by himself. The prize was awarded to Charles Vaude, for his lyric 'Kosciusko,' and Miss Nella Webb produced this song with instantaneous success."--P. [4].; Also available online http://nla.gov.au/nla.mus-an8393500; 1913, by Victor J. Draper, Sydney.; NLA's NL copy from the collection of Keith Watson. ANL
Letter containing inquiry regarding the ethnic identity of the descendents of Georg Moritz Oppenheim.
No full textLetter from Wilhelm Gehlig to Rabbi Dr. Freudenthal in Nuremberg with a genealogical question regarding Georg Moritz Oppenheim. Of particular interest to the author is to determine whether Oppenheim's descendents are "rein jüdischen Blutes (=of pure Jewish blood)."Robert Singermandigitize
Design, Synthesis and Standard Characterisations of Organic Compounds for Organic Electronics
No full textInvited by Dr Moritz Riede (University of Oxford) for the SEPOMO Network School, St Anne’s College, Oxford (UK)Séminair
Conventional and circular economy compliant modification strategies for recycled polypropylene
No full textAuthor Moritz MagerMasterarbeit Universität Linz 2021Arbeit gesperr
Conventional and circular economy compliant modification strategies for recycled polypropylene
No full textAuthor Moritz MagerMasterarbeit Universität Linz 2021Arbeit gesperr
Fullerenes and their cross-linking in organic and perovskite solar cells
No full textThis thesis is concerned with the photo-dimerisation mechanism of C60 in bulk hetero-junction (BHJ) organic solar cells, its effect on device performance and the use of cross-linked fullerenes as electron selective layers (ESL) for perovskite solar cells.
The photo-dimerisation of fullerenes has recently been identified as negatively impacting the stability of BHJs but the process is incompletely understood in BHJs. By employing model systems, we independently study the effects of donor (D) energetics and morphology. We find that for donors forming charge transfer (CT) states much lower in energy than the lowest energy C60 excitons, the dimerisation is suppressed at only 5% D loading. This is in contrast to Ds forming CT states with energies comparable to C60 excitons, for which dimerisation is suppressed from 20% donor loading. It is also found that the electron affnity (EA) increases by 100 meV after dimerization but that CT states remain unaffected. These observations are combined into a complete model of dimerisation in BHJs. It is concluded that avoiding dimerisation requires either low D band-gaps, a deliberate energy loss or low electron mobilities.
Thus the effect of dimerisation on devices is revisited. From our knowledge of which systems do and do not dimerise and temporal arguments, losses in performance induced by dimerisation and other extrinsic effects are de-convoluted. Surprisingly no significant degradation is found to originate from dimerization. By contrast, we observe sever performance losses similar to those previously attributed to dimerisation, which we suggested to be caused by the MoO3 hole transport layer, which is commonly employed in OPV.
Lastly we address the problem of C60 dissolution upon perovskite deposition from solution. To avoid dissolution, two cross-linkable fullerenes are introduced as ESLs. Both display good morphological and electronic characteristics and resulted in greatly improved photo-voltaic performance compared to C60. This is attributed to the avoided dissolution, which because of a likely reduction in pin-holes and inhomogeneities, suppresses surface recombination with the FTO electrode.</p
Sensitive external quantum efficiency measurements for studying charge transfer in organic solar cells
No full textCharge transfer (CT) states, which form at the interface between donor and acceptor molecules in organic solar cells (OSCs), strongly influence device performance, in particular the open-circuit voltage and the photogeneration of free charges. However, the connection between molecular properties, the resulting energetics at the donor-acceptor interface, and ultimately device performance is still incompletely understood. To address this knowledge gap, this thesis studies the impact of (1) molecular energy levels and donor:acceptor mixing ratios on exciton separation, and (2) blend morphologies on interfacial energetic disorder and voltage losses. CT state properties are studied via a custom-built sensitive external quantum efficiency (EQE) setup and fit from the resulting spectra. In the first part of this thesis, we establish a reliable and reproducible fitting methodology that considers both singlet and CT state absorption contributions in the EQE. We first apply this methodology to study the impact of molecular energy levels on exciton separation in low donor content blends of ZnPc or its fluorinated derivatives (FxZnPc, with x = 0, 4, 8, 16) and C60. We find that the fluorination-induced shifts of the donor energy levels result in an increasing CT state energy with C60 and a decreasing offset between local excitation (LE) and CT states. Through in-depth characterization of molecular and blend energy levels, we draw a comprehensive picture of how LE, CT, and charge separated (CS) energy levels and the energetic transitions between states change upon fluorination of ZnPc. We find that the CT → CS transition presents a major bottleneck for free charge generation in the low offset F8ZnPc and F16ZnPc blends. This study is further extended beyond the low donor content blends by gradually varying the donor:acceptor mixing ratio from neat FxZnPc to neat C60. We find that with increasing F8ZnPc or F16ZnPc content, the CT dissociation efficiency is further reduced, leading to very low photocurrents in these blends. The dependence of CT dissociation on donor concentration is attributed to charge-quadruple induced electrostatic shifts, caused by the positive quadrupole moments of F8ZnPc/F16ZnPc, which increase the CT dissociation barrier with increasing donor content. In comparison, ZnPc/F4ZnPc, which have negative quadrupole moments, experience the opposite electrostatic shifts and show efficient CT dissociation across all donor:C60 mixing ratios. These results not only motivate further studies of the CS state, but also show that improving the CT → CS transition, for instance via the design of molecules with suitable quadrupole moments, is an effective route for increasing the photocurrents of OSCs. Finally, we study the impact of interfacial energetic disorder on device performance and voltage losses for five small molecule donor:C60 systems. Through temperature-dependent EQE measurements, we disentangle the contributions of static (i.e. temperature independent) and dynamic (i.e. temperature-dependent) disorder. Contrary to what is often stated for evaporated blends of small molecules, static disorder is found to be significant, and often exceed the contribution of dynamic disorder in the CT linewidth. This motivates future studies of interfacial disorder in OSCs, linking bulk and interface morphologies to device performance, and finding ways to reduce disorder to decrease voltage losses
An exploration of vacuum evaporable non-fullerene acceptors for use in organic solar cells and molecular orientation in evaporated thin films
No full textOrganic solar cells (OSCs) offer an attractive pathway for next-generation photovoltaic technologies. Recent advances in molecular design have advanced the technology with the advent of non-fullerene acceptors (NFAs). NFAs have enabled rapid efficiency gains in OSCs, with state-of-the-art OSCs showcasing efficiencies of close to 20%. These advances are constrained to the solution processing field and are not compatible with vacuum deposition, a more industrially mature and commercially relevant manufacturing method which also eliminates the need for solvent use and related components in the fabrication process. In the first part of this thesis various NFA molecules, specifically oligothiophenes and a perylene diimide, are investigated for use as a vacuum evaporable NFA. the investigation focused on studying the optical and energetic behaviour, primarily using spectroscopic ellipsometry (SE) and ambient photoelectron spectroscopy, of these materials. Based on the results, the oligiothiophene BTIC-H was identified as a strong candidate for use in vacuum evaporated NFA OSCs with a good extinction coefficient k = 0.6, and a HOMO and LUMO of −5.9 and −3.6 eV, respectively. Planar and bulk heterojunction devices using BTIC-H were explored. PHJ devices showcased promising performance (good VOC ≈ 1V with low voltage losses ≈ 0.8 V), however, photocurrents in BHJ devices were poor (≈ 0.5 mA/cm2). These results showed that there is very real promise for vacuum evaporable NFAs, however, significant optimisation of devices as well as molecular design are needed. The second part of this thesis explored a comprehensive analysis of molecular orientation in vacuum evaporated organic thin films, a concept which is often poorly understood but plays a critical role in the photophysics of organic electronics. This was done using SE and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Three different molecules were investigated, namely alpha-sexithiophene, the merocyanine dye HB194, and the donor-acceptor (DA) type donor DTDCPB. NEXAFS was used to calculate the mean facial orientation of the molecules while SE was used to calculate the backbone orientation, with the results supplemented by grazing incidence wide-angle X-ray scattering (GIWAXS). Results were compared to literature, showing strong agreement in the case of alpha-sexithiophene and revealing significant changes in orientation upon substrate heating, which were broken down into their respective facial and backbone orientation changes. These results showed that understanding both the facial and backbone changes reveal rich information about the microstructure of organic thin films and provide a foundation for more comprehensive analysis of blended films which may reveal device relevant insights
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