singlet fission (sf)has been regarded as the most promising molecular strategy to break the shockley–queisserlimit on power conversion ef#64257;ciency (pce) of single junction solar cells, significantlyraising it from 33% to 44%. singlet fission is a multiple exciton process in whichan organic chromophore in an excited state shares it energy with a neighboringground-state chromophore and both are converted into triplet excited states. singletfission, like many other internal conversion processes, takes place on a picosecondor even sub-picosecond time scale, thus causing the difficulty in singletfission study. ultrafast transient absorption spectroscopy enablesinvestigation of photophysical and photochemical reactions taking place on timescalesranging from tens of femtoseconds to a few nanoseconds in real time and thusopened a new era of research in singlet fission.
intramolecularsinglet #64257;ssion (isf) is a more suitable approach in practical applicationcompared with intermolecular singlet fission (xsf). the latter is prone to beaffected by crystal packing, morphology, and other factors. for example, onlywhen neighboring chromophores are electronically coupled in the solid state orby diffusive collisions in highly concentrated solutions that acenes canundergo xsf. though isf has been observed in crystalline solids and aggregates of oligoacenes, these two arenot the most appropriate candidates for implementing high-efficiency sf-basedsolar cells because of their high band gap and low mobility. compared with crystalline solids andaggregates of oligoacenes, conjugated polymers have a low-bandgap, and can be easilyprocessed into thin films with good phase separation. for these reasons, wedecided to study the polymer isf systems — tetrakis-pentaphenyl spirobifluorenesystems.
given theadvantageous structural properties of the tetracene side chain, we aim toexplore this side chain effect on singlet fission. this project will combinethe observed population kinetics and quantum chemistry calculation methods tofurther explore the intramolecular singlet fission in these molecules. andexplore the intramolecular dynamics through the excited state kineticsexperiments in the solution phase and the membrane phase. study how to balancethe intramolecular and intermolecular processes, and obtain more tripletexcitons in sf materials in the preparation of devices, and finally improvedevice efficiency.
the goal of thisproject is to assess the impact of the tetracene side chain on the singlefission yields. combine single molecule and membrane phase experiments togetherto explore the intramolecular singlet fission. this project is dedicated to theapplication of isf materials in device to improve the photoelectric conversionefficiency of solar cell systems.
1. week 1-2: reviewrelevant literature, clarify the research content, determine the plan, andcomplete the opening report;
2. weeks 3-4: studyof theoretical knowledge and practical operation of laboratory instruments andequipment;
3. weeks 5-10:ultrafast transient spectroscopy analysis of tetrakis-pentaphenylspirobifluorene;
1. j. hu et al., newinsights into the design of conjugated polymers for intramolecular singletfission. nature communication 9, 2999 (2018).
2. s. n. sanders etal., exciton correlations in intramolecular singlet fission. journal of theamerican chemical society 138, 7289-7297 (2016).
3. s. n. sanders etal., quantitative intramolecular singlet fission in bipentacenes. journal ofthe american chemical society 137, 8965-8972 (2015).
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