Abstract
Singlet exciton fission is a mechanism that could potentially enable solar cells to surpass the Shockley-Queisser efficiency limit by converting single high-energy photons into two lower-energy triplet excitons with minimal thermalization loss. The ability to make use of singlet exciton fission to enhance solar cell efficiencies has been limited, however, by the sparsity of singlet fission materials with triplet energies above the bandgaps of common semiconductors such as Si and GaAs. Here, we employ a high-throughput virtual screening procedure to discover new organic singlet exciton fission candidate materials with high-energy (>1.4 eV) triplet excitons. After exploring a search space of 4482 molecules and screening them using time-dependent density functional theory, we identify 88 novel singlet exciton fission candidate materials based on anthracene derivatives. Subsequent purification and characterization of several of these candidates yield two new singlet exciton fission materials: 9,10-dicyanoanthracene (DCA) and 9,10-dichlorooctafluoroanthracene (DCOFA), with triplet energies of 1.54 eV and 1.51 eV, respectively. These materials are readily available and low-cost, making them interesting candidates for exothermic singlet exciton fission sensitization of solar cells. However, formation of triplet excitons in DCA and DCOFA is found to occur via hot singlet exciton fission with excitation energies above ∼3.64 eV, and prominent excimer formation in the solid state will need to be overcome in order to make DCA and DCOFA viable candidates for use in a practical device.
Highlights
Introduction to singlet exciton fissionSinglet exciton fission is a down-conversion process in organic semiconductors that spontaneously converts one spinsinglet electron-hole pair into two spin-triplet excitons.1 Each triplet exciton carries approximately half the energy of the initial singlet exciton
Formation of triplet excitons in DCA and DCOFA is found to occur via hot singlet exciton fission with excitation energies above ∼3.64 eV, and prominent excimer formation in the solid state will need to be overcome in order to make DCA and DCOFA viable candidates for use in a practical device
In order to limit our parameter space, we focus on known molecules with an anthracene core and a smaller fraction of combinatorically generated anthracene derivatives, in contrast to the large combinatorial fragment-based libraries that are often employed in high-throughput virtual screening projects for organic materials
Summary
Introduction to singlet exciton fissionSinglet exciton fission is a down-conversion process in organic semiconductors that spontaneously converts one spinsinglet electron-hole pair (exciton) into two spin-triplet excitons. Each triplet exciton carries approximately half the energy of the initial singlet exciton. Conventional single-junction solar cells are limited in efficiency to about 34% (the Shockley-Queisser limit), largely due to loss from unabsorbed below-bandgap photons and thermalization of high-energy excitons.. When combined with a lower-bandgap semiconductor, singlet exciton fission materials raise the theoretical efficiency limit of a single-junction solar cell by reducing thermalization of excitons generated by high-energy scitation.org/journal/jcp photons. It has been calculated that the maximum power conversion efficiency of a single-junction photovoltaic device incorporating a layer of materials that can undergo singlet exciton fission is 44.4%.3. Singlet exciton fission yields no advantage to the power efficiency of solar cells because the potential increase in photocurrent is matched by a decrease in the open circuit voltage.. In combination with silicon, a singlet exciton fission material ideally absorbs all photons with energies greater than twice the silicon bandgap.. In combination with silicon, a singlet exciton fission material ideally absorbs all photons with energies greater than twice the silicon bandgap. The resulting excitons are split into two excitons at or just above the silicon bandgap and transferred to silicon, where they supplement silicon photocurrent generated from direct absorption of photons with energies between the silicon bandgap and twice the silicon bandgap.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
