Triplet-triplet annihilation (TTA) is an energy transfer mechanism where two molecules in their triplet excited states interact to form a ground state molecule and an excited molecule in its singlet state.[1] This mechanism is example of Dexter energy transfer mechanism.[2] In triplet-triplet annihilation, one molecule transfers its excited state energy to the second molecule, resulting in the first molecule returning to its ground state and the second molecule being promoted to a higher excited singlet state.[1]
A Jablonski diagram describing the mechanism of triplet-triplet annihilation. The energy of the first triplet excited state (T1) is transferred to a second triplet excited state (T1), resulting in (1) the first T1 returning to the singlet ground state S0 and (2) the second T1 promoting to the singlet excited state (S1).
Triplet-triplet annihilation was first discovered in the 1960s to explain the observation of delayed fluorescence in anthracene derivatives.[3][4][5][6]
A Jablonski diagram describing the sensitization process in triplet-triplet annihilation upconversion. The sensitizer first absorbs light and reaches its first singlet excited state (S1). The sensitizer S1 state undergoes intersystem crossing (ISC) to the triplet excited state (T1). The sensitizer then transfers energy to the emitter, which returns the sensitizer T1 to the ground state (S0) and promotes the emitter to its T1.
Triplet-triplet annihilation combines the energy of two triplet-excited molecules onto one molecule to produce a higher excited state. Since the higher excited state is an emissive singlet state, TTA can be used to achieve photon upconversion which is a process that converts the energy of two photons into one photon of higher energy.[7][8] To achieve photon upconversion through triplet-triplet annihilation two types of molecules are often combined: a sensitizer and an emitter (annihilator).[9] The sensitizer absorbs the low energy photon and populates its first excited triplet state (T1) through intersystem crossing. The sensitizer then transfers the excitation energy to the emitter, resulting in a triplet excited emitter and a ground state sensitizer. Two triplet-excited emitters can then undergo triplet-triplet annihilation to produce a singlet excited state (S1) of the emitter, which can emit an upconverted photon.
Requirementsedit
For efficient TTA upconversion, the sensitizer should absorb strongly in the desired excitation range and have high conversion efficiency from the singlet excited state to the triplet excited state.[9] The emitter should have a singlet energy level just below twice the energy of the first triplet excited state. Both the emitter and sensitizer should have long triplet-state lifetimes so that the TTA mechanism has enough time to occur.[9]
Applicationsedit
Triplet-triplet annihilation upconversion (TTA-UC) materials have the advantages of needing low excitation power and having changeable emission and excitation light wavelengths.[10] Due to these advantages, many applications of TTA-UC materials have been explored.
Solar cellsedit
Solar cells are electrical devices that convert sunlight to electricity. However, due to the properties of the materials composing solar cells, many solar cells do not harvest low energy (with wavelength above 800 nm) photons efficiently. Thus, the ability for TTA-UC materials to combine the energy of two low energy photons into one high energy photon is desirable to capture more of the energy from sunlight.[9]
Organic light-emitting diodesedit
Light-emitting materials that can convert non-emissive triplet states into emissive singlet states are crucial in organic light-emitting diodes (OLEDs) as, statistically, 75% of the excited states formed in an OLED are triplet states.[11] TTA materials are well suited to use in OLEDs due to their low operational voltage, small drop-off in efficiency when increasing brightness, and low cost. However, most TTA materials emit photons that are blue to deep blue, which limits their applications in OLEDs until the colour variety diversifies.[9]
Cancer therapyedit
In photolysis cancer therapy, light is used to selectively break bonds which releases and activates a target drug molecule. The drug molecule can be released near or in tumour sites to combat the disease. TTA-UC materials that can be excited by near-infrared light are desirable for this application since near-infrared light penetrates tissue well.[10]
Referencesedit
^ abTurro, Nicholas J. (2010). Modern molecular photochemistry of organic molecules. V. Ramamurthy, J. C. Scaiano. Sausalito, Calif. ISBN978-1-891389-25-2. OCLC 396185412.{{cite book}}: CS1 maint: location missing publisher (link)
^Monguzzi, A.; Tubino, R.; Meinardi, F. (2008-04-22). "Upconversion-induced delayed fluorescence in multicomponent organic systems: Role of Dexter energy transfer". Physical Review B. 77 (15): 155122. Bibcode:2008PhRvB..77o5122M. doi:10.1103/PhysRevB.77.155122. ISSN 1098-0121.
^Parker, C. A.; Hatchard, C. G. (1962). "Delayed fluorescence from solutions of anthracene and phenanthrene". Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences. 269 (1339): 574–584. Bibcode:1962RSPSA.269..574P. doi:10.1098/rspa.1962.0197. S2CID 98155331.
^Parker, C. A.; Hatchard, C. G. (1962). "Sensitized Anti-Stokes Delayed Fluorescence". Proc. Chem. Soc.: 386–387. doi:10.1039/PS9620000373.
^Parker, C. A. (1963). "Sensitized P -type delayed fluorescence". Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences. 276 (1364): 125–135. Bibcode:1963RSPSA.276..125P. doi:10.1098/rspa.1963.0197. S2CID 97502195.
^Parker, C. A.; Joyce, Thelma A. (1967). "Delayed fluorescence of anthracene and some substituted anthracenes". Chemical Communications (15): 744. doi:10.1039/C19670000744.
^Singh-Rachford, Tanya N.; Castellano, Felix N. (2010). "Photon upconversion based on sensitized triplet–triplet annihilation". Coordination Chemistry Reviews. 254 (21–22): 2560–2573. doi:10.1016/j.ccr.2010.01.003.
^Gray, Victor; Moth-Poulsen, Kasper; Albinsson, Bo; Abrahamsson, Maria (2018). "Towards efficient solid-state triplet–triplet annihilation based photon upconversion: Supramolecular, macromolecular and self-assembled systems". Coordination Chemistry Reviews. 362: 54–71. doi:10.1016/j.ccr.2018.02.011.
^ abZeng, Le; Huang, Ling; Han, Jinfeng; Han, Gang (2022-09-20). "Enhancing Triplet–Triplet Annihilation Upconversion: From Molecular Design to Present Applications". Accounts of Chemical Research. 55 (18): 2604–2615. doi:10.1021/acs.accounts.2c00307. ISSN 0001-4842. PMID 36074952. S2CID 252160565.
^Wang, Jianpu; Chepelianskii, Alexei; Gao, Feng; Greenham, Neil C. (2012-11-13). "Control of exciton spin statistics through spin polarization in organic optoelectronic devices". Nature Communications. 3 (1): 1191. Bibcode:2012NatCo...3.1191W. doi:10.1038/ncomms2194. ISSN 2041-1723. PMC3514489. PMID 23149736.
December 18, 2023
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Triplet triplet annihilation TTA is an energy transfer mechanism where two molecules in their triplet excited states interact to form a ground state molecule and an excited molecule in its singlet state 1 This mechanism is example of Dexter energy transfer mechanism 2 In triplet triplet annihilation one molecule transfers its excited state energy to the second molecule resulting in the first molecule returning to its ground state and the second molecule being promoted to a higher excited singlet state 1 A Jablonski diagram describing the mechanism of triplet triplet annihilation The energy of the first triplet excited state T1 is transferred to a second triplet excited state T1 resulting in 1 the first T1 returning to the singlet ground state S0 and 2 the second T1 promoting to the singlet excited state S1 Triplet triplet annihilation was first discovered in the 1960s to explain the observation of delayed fluorescence in anthracene derivatives 3 4 5 6 Contents 1 Photon upconversion 1 1 Requirements 1 2 Applications 1 2 1 Solar cells 1 2 2 Organic light emitting diodes 1 2 3 Cancer therapy 2 ReferencesPhoton upconversion edit nbsp A Jablonski diagram describing the sensitization process in triplet triplet annihilation upconversion The sensitizer first absorbs light and reaches its first singlet excited state S1 The sensitizer S1 state undergoes intersystem crossing ISC to the triplet excited state T1 The sensitizer then transfers energy to the emitter which returns the sensitizer T1 to the ground state S0 and promotes the emitter to its T1 Triplet triplet annihilation combines the energy of two triplet excited molecules onto one molecule to produce a higher excited state Since the higher excited state is an emissive singlet state TTA can be used to achieve photon upconversion which is a process that converts the energy of two photons into one photon of higher energy 7 8 To achieve photon upconversion through triplet triplet annihilation two types of molecules are often combined a sensitizer and an emitter annihilator 9 The sensitizer absorbs the low energy photon and populates its first excited triplet state T1 through intersystem crossing The sensitizer then transfers the excitation energy to the emitter resulting in a triplet excited emitter and a ground state sensitizer Two triplet excited emitters can then undergo triplet triplet annihilation to produce a singlet excited state S1 of the emitter which can emit an upconverted photon Requirements edit For efficient TTA upconversion the sensitizer should absorb strongly in the desired excitation range and have high conversion efficiency from the singlet excited state to the triplet excited state 9 The emitter should have a singlet energy level just below twice the energy of the first triplet excited state Both the emitter and sensitizer should have long triplet state lifetimes so that the TTA mechanism has enough time to occur 9 Applications edit Triplet triplet annihilation upconversion TTA UC materials have the advantages of needing low excitation power and having changeable emission and excitation light wavelengths 10 Due to these advantages many applications of TTA UC materials have been explored Solar cells edit Solar cells are electrical devices that convert sunlight to electricity However due to the properties of the materials composing solar cells many solar cells do not harvest low energy with wavelength above 800 nm photons efficiently Thus the ability for TTA UC materials to combine the energy of two low energy photons into one high energy photon is desirable to capture more of the energy from sunlight 9 Organic light emitting diodes edit Light emitting materials that can convert non emissive triplet states into emissive singlet states are crucial in organic light emitting diodes OLEDs as statistically 75 of the excited states formed in an OLED are triplet states 11 TTA materials are well suited to use in OLEDs due to their low operational voltage small drop off in efficiency when increasing brightness and low cost However most TTA materials emit photons that are blue to deep blue which limits their applications in OLEDs until the colour variety diversifies 9 Cancer therapy edit In photolysis cancer therapy light is used to selectively break bonds which releases and activates a target drug molecule The drug molecule can be released near or in tumour sites to combat the disease TTA UC materials that can be excited by near infrared light are desirable for this application since near infrared light penetrates tissue well 10 References edit a b Turro Nicholas J 2010 Modern molecular photochemistry of organic molecules V Ramamurthy J C Scaiano Sausalito Calif ISBN 978 1 891389 25 2 OCLC 396185412 a href Template Cite book html title Template Cite book cite book a CS1 maint location missing publisher link Monguzzi A Tubino R Meinardi F 2008 04 22 Upconversion induced delayed fluorescence in multicomponent organic systems Role of Dexter energy transfer Physical Review B 77 15 155122 Bibcode 2008PhRvB 77o5122M doi 10 1103 PhysRevB 77 155122 ISSN 1098 0121 Parker C A Hatchard C G 1962 Delayed fluorescence from solutions of anthracene and phenanthrene Proceedings of the Royal Society of London Series A Mathematical and Physical Sciences 269 1339 574 584 Bibcode 1962RSPSA 269 574P doi 10 1098 rspa 1962 0197 S2CID 98155331 Parker C A Hatchard C G 1962 Sensitized Anti Stokes Delayed Fluorescence Proc Chem Soc 386 387 doi 10 1039 PS9620000373 Parker C A 1963 Sensitized P type delayed fluorescence Proceedings of the Royal Society of London Series A Mathematical and Physical Sciences 276 1364 125 135 Bibcode 1963RSPSA 276 125P doi 10 1098 rspa 1963 0197 S2CID 97502195 Parker C A Joyce Thelma A 1967 Delayed fluorescence of anthracene and some substituted anthracenes Chemical Communications 15 744 doi 10 1039 C19670000744 Singh Rachford Tanya N Castellano Felix N 2010 Photon upconversion based on sensitized triplet triplet annihilation Coordination Chemistry Reviews 254 21 22 2560 2573 doi 10 1016 j ccr 2010 01 003 Gray Victor Moth Poulsen Kasper Albinsson Bo Abrahamsson Maria 2018 Towards efficient solid state triplet triplet annihilation based photon upconversion Supramolecular macromolecular and self assembled systems Coordination Chemistry Reviews 362 54 71 doi 10 1016 j ccr 2018 02 011 a b c d e Gao Can Wong Wallace W H Qin Zhengsheng Lo Shih Chun Namdas Ebinazar B Dong Huanli Hu Wenping 2021 10 01 Application of Triplet Triplet Annihilation Upconversion in Organic Optoelectronic Devices Advances and Perspectives Advanced Materials 33 45 2100704 Bibcode 2021AdM 3300704G doi 10 1002 adma 202100704 hdl 11343 299048 ISSN 0935 9648 PMID 34596295 S2CID 238237517 a b Zeng Le Huang Ling Han Jinfeng Han Gang 2022 09 20 Enhancing Triplet Triplet Annihilation Upconversion From Molecular Design to Present Applications Accounts of Chemical Research 55 18 2604 2615 doi 10 1021 acs accounts 2c00307 ISSN 0001 4842 PMID 36074952 S2CID 252160565 Wang Jianpu Chepelianskii Alexei Gao Feng Greenham Neil C 2012 11 13 Control of exciton spin statistics through spin polarization in organic optoelectronic devices Nature Communications 3 1 1191 Bibcode 2012NatCo 3 1191W doi 10 1038 ncomms2194 ISSN 2041 1723 PMC 3514489 PMID 23149736 Retrieved from https en wikipedia org w index php title Triplet triplet annihilation amp oldid 1189654841, wikipedia, wiki, book, books, library,
