Singlet Fission

Abstract

where he stayed and became a full professor in 1975 and served as chairman in -1984. In 1986 he held the M. K. Collie-Welch Regents Chair in Chemistry at the University of Texas at Austin, and subsequently moved to the University of Colorado at Boulder. He now shares his time equally between his research groups at Boulder and in Prague, Czech Republic, where he works at the Academy of Sciences. He is a Fellow of the American Chemical Society and a member of the U.S. National Academy of Sciences, the American Academy of Arts and Sciences, the Czech Learned Society, and the International Academy of Quantum Molecular Science. Dr. Michl's current research interests are the photophysics of solar cells; organic photochemistry; nanoscience, especially new ways of attaching molecules to metal surfaces and preparing artificial surface-mounted molecular rotors; chemistry of lithium, boron, silicon, and fluorine; and use of quantum chemical and experimental methods for better understanding of molecular electronic structure. He has been the Editor of Chemical Reviews since 1984.

In situ measurement of exciton energy in hybrid singlet-fission solar cells

“…One strategy is to sensitize a low bandgap semicon ductor with a higher bandgap material that can generate additional photocurrent from absorbed high energy photons 6,9 . Such an opportunity is offered by singlet fission, which is the spin conserving process by which a spin singlet exciton on an organic chromophore splits to form a pair of lower energy triplet excitons on neighbouring molecules 10 . Transient optical absorption measurements suggest that this process can be highly efficient, as we have observed singlet fis sion occurring on an 80 fs timescale in pentacene 11 .…”

“…Pentacene is an attractive material for a sensitizer as it under goes efficient singlet fission [11][12][13] and has high hole mobility 14 , but the triplet energy is challenging to determine because of the van ishingly small photoluminescence quantum yield of pentacene 10,15 . In the solid state the triplet energy has been measured indirectly using variable temperature host guest fluorescence 16 , electron backscattering from crystalline pentacene 17 , and inelastic tunnel ling spectroscopy on amorphous pentacene 18 .…”

Multiple exciton generation in quantum dot-based solar cells

“…Here, additional charges are produced from energy that would otherwise have been lost as heat. Such processes have been demonstrated to occur efficiently in organic semiconductors and inorganic quantum dots (QDs), where the phenomena are termed singlet exciton fission [17][18][19] and multiple exciton generation (MEG) [7,20,21], respectively. It has been calculated that such CM mechanisms can raise the maximum efficiency of single-junction PVs from about 33% to almost 44% (see Figure 1B) [22].…”

Coherent Dynamics of Mixed Frenkel and Charge-Transfer Excitons in Dinaphtho[2,3-b:2′3′-f]thieno[3,2-b]-thiophene Thin Films: The Importance of Hole Delocalization

“…CT states can act as precursors for interfacial CT states [33][34][35]; mixing of CT states with Frenkel excitons would facilitate charge separation in photovoltaic materials. They have also gained recent attention due to their relevance to singlet fission [36][37][38], in which singlet to triplet conversion can proceed via sequential CT steps [39][40][41].Here we focus on dinaphtho[2,3-b:, a p-type OSC originally introduced by Takimiya and co-workers [42]. DNTT and its derivatives [5,[43][44][45][46][47][48][49] have gained attention due to their high hole mobility values and air stability.…”

“…CT states can act as precursors for interfacial CT states [33][34][35]; mixing of CT states with Frenkel excitons would facilitate charge separation in photovoltaic materials. They have also gained recent attention due to their relevance to singlet fission [36][37][38], in which singlet to triplet conversion can proceed via sequential CT steps [39][40][41].…”