Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 16 of 16 for “"Singlet exciton fission"”.
-
Singlet exciton fission : applications to solar energy harvesting
Singlet exciton fission transforms a single molecular excited state into two excited states of half the energy. When used in solar cells it can double the photocurrent from high energy photons increasing the maximum theoretical power efficiency to greater than 40%. The steady state singlet fission …
-
Singlet Exciton Fission in Acene Dimer and Diradicaloid Molecules
… that leads to ultrafast generation of triplet excitons following photoexcitation, singlet exciton fission, in three different acene dimers and diradicaloids. In pentacene and tetracene dimers, we investigate their mechanism of singlet fission. In a series of diradicaloids, we study the relation …
-
Singlet exciton fission, a multi-exciton generation process, in organic semiconductor solar cells
… work we explore implementations of a multiple exciton generation process, singlet exciton fission, to work around the Shockley-Queisser limit, according to which, all single junctions cells have a theoretical efficiency limit of 33.7%. This is the first implementation of a singlet fission …
-
Singlet exciton fission-enhanced silicon photovoltaics: Interfacial engineering, device design and spectroscopic technique development
… the bandgap absorbed by silicon is lost as heat. Singlet exciton fission in organic molecules has been proposed to reduce these losses. By having the organic layer absorb the high energy light and transferring the triplet excitons generated from the singlet fission process to silicon, the …
-
Singlet fission photovoltaics
… than the bandgap lose energy by thermalization. Singlet exciton fission splits a high-energy molecular excitation ("singlet" exciton) into a pair of lowenergy ones ("triplet" excitons). In solar cells, it promises to generate two electrons per photon, potentially overcoming the singlet junction …
-
Fluctuations and exciton dynamics in molecular semiconductors
… structure of molecular semiconductors and of the exciton dynamics in the same materials. The method employed in this thesis is time- and angle-resolved photoemission spectroscopy. In the first part, the electronic structure of molecular semiconductors at equilibrium is considered. We show that the …
-
Sensitized energy transfer for organic solar cells, optical solar concentrators, and solar pumped lasers
The separation of chromophore absorption and excitonic processes, such as singlet exciton fission and photoluminescence, offers several advantages to the design of organic solar cells and luminescent solar concentrators (LSCs) for the end goal of achieving a lower cost solar energy generation. This …
-
Ultrafast Spectroscopy of Organic Semiconductors: Singlet Fission and Nonfullerene Acceptors for Organic Photovoltaics
… The first takes advantage of a process called singlet exciton fission, and the second embodies an exodus from the fullerene electron acceptors prominent in organic solar cells. Indeed, this versatile class of tunable small molecules are aptly termed nonfullerene acceptors. However, both …
-
Excitonic spin engineering in optoelectronic devices
… efficiencies to 35% or higher. First, we utilize singlet exciton fission as a downconverting layer. Singlet exciton fission is a process in which a single high energy exciton fissions into two excitons of half the energy. Here, we first demonstrate the potential of singlet fission in an …
-
Singlet Fission Organic Solar Cell with Long-Wavelength Absorption Using Non-fullerene Acceptors
Organic solar cells made with singlet exciton fission materials are able to convert a single photon into two charges. Paired with a long-wavelength absorbing acceptor material, singlet fission materials enable solar cells that exhibit the quantum efficiency benefits of a multi-junction solar cell, …
-
Investigating the Photophysics of New and Stable Singlet Fission Materials
… our investigations into the mechanism of singlet exciton fission, examining the effects of morphology, aromaticity, and photoluminescence yield on the fission process, and developing generalised principles to aid the design of new materials. Singlet fission is the process of forming two …
-
Pushing the Boundaries of Endothermic Singlet Fission in Organic Semiconductors through Structure and Energetic Control
Singlet exciton fission (SF) is an exciton multiplication process in organic semiconductors in which a photoexcited singlet exciton is converted to two triplet excitons. SF based solar cells help break the Shockley-Quisser limit as high energy photons are used to generate two electron-hole pairs …
-
Energy level engineering in colloidal quantum dot solar cells
… of PbS QDs can be used to elucidate charge- and exciton-transfer processes within hybrid organic /QD photovoltaic devices that demonstrate singlet exciton fission. We find that PbS QDs can accept electrons from triplets generated by singlet fission in pentacene and act as low-bandgap light …
-
Chemical Modifications and Passivation Approaches in Metal Halide Perovskite Solar Cells
… yield. Finally, we explored the possibility of singlet exciton fission between low bandgap perovskites and tetracene as the triplet sensitizer finding no significant energy transfer between the two. We then used tetracene as an efficient dopant-free hole transport layer providing clean …
-
On exciton-vibration and exciton-photon interactions in organic semiconductors
… is dominated by bound electron-hole pairs called excitons, which are often strongly affected by hundreds of possible molecular vibrations. Although quantum theory contains all the ingredients to describe these complex phenomena, in practice it is only possible to solve the corresponding equations …
-
Interfacial engineering and spectroscopy of spin-triplet excitons for singlet fission sensitization of silicon solar cells
… loss of a third of all incident solar energy. Singlet exciton fission, an energy-splitting process that converts single high-energy photons into multiple lower-energy excited states, has the capability to reduce thermalization losses and boosts the maximum silicon solar cell efficiency from …