本文提出了使用共軛有機磁場效應研究在熱活化對於單重態裂變(Singlet fission)機制的比較。單重態機制過程是單重態激子(S0+ S1)變成中間態1(TT)分解成兩個離散的三重態激子（T1 + T1），過程反應中的中間態1(TT)的重要性不容小覷，此研究討論不同S1到中間態的能階差對於單重態裂變的影響，使用有著單重態裂變反應的有機半導體並四苯(Tetracene)和紅熒烯(Rubrene)。這兩個材料有著相似的化學結構及近似的單重態最低能階，有利於實驗比較。結果中呈現Rubrene相較於Tetracene在單重態裂變機制中，單重態激子到中間態有著更小的能量差，因此發生單重態裂變機制過程受熱活化有著較小的影響。並凸顯了Rubrene有著比Tetracene更多的波段可發生單重態裂變機制，更利於討論磁場效應，這將是影響有機半導體在磁場效應的關鍵。

This paper presents a comparison of the mechanism of Singlet fissionn(SF) in thermal activation using conjugated organic magnetic field effects. The singlet mechanism process is that the singlet exciton (S0 + S1) becomes the TT pair and decomposes into two discrete triplet excitons (T1 + T1). The importance of the TT pair in the process reaction cannot be accommodated. Briefly, this study discusses the influence of the energy level difference from different S1 to the intermediate state on the SF. The organic semiconductors Tetracene and Rubrene with SF reaction are used. These two materials have similar chemical structures and approximate singlet lowest energy levels, which is conducive to experimental comparison. The results show that Rubrene has a smaller energy difference between singlet excitons and intermediate states in the SF mechanism than Tetracene, so the process of SF mechanism is less affected by thermal activation. It also highlights that Rubrene has a SF mechanism with more wavelengths than Tetracene, which is more conducive to discussing the magnetic field effect, which will be the key to the magnetic field effect of organic semiconductors.

[1] M. Pope, “Electroluminescence in organic crystals”, J. Chem. Phys. 38, 2043 (1963).
[2] C. K. Chiang, C. R. Fincher, Y. W. Park, A. J. Heeger, H. Shirakawa, E. J. Louis, S. C. Gau, A. G. Macdiarmid, “Electrical conductivity in doped polyacetylene”, Phys. Rev. Lett. 39, 1098 (1977).
[3] C. W. Tang, S. A. VanSlyke, “Organic electroluminescent diodes”, Appl. Phys. Lett. 51, 913 (1987).
[4] Y. Ma, H. Zhang, J. Shen, C. Che, “Electroluminescence from triplet metal—ligand charge-transfer excited state of transition metal complexes”, Synth. Met. 94, 245 (1998).
[5] G. Gustafsson, Y. Cao, G. M. Treacy, F. Klavetter, N. Colaneri, A. J. Heeger, “Flexible light-emitting diodes made from soluble conducting polymers”, Nature 357, 477 (1992).
[6] M. A. Baldo, D. O. Brien, Y. You, A. Shoustikov, S. Sibley, M. Thompson, S. Forrest, “Highly efficient phosphorescent emission from organic electroluminescent devices”, Nature 395, 151 (1998).
[7] M. A. Baldo, M. E. Thompson, S. R. Forrest, “High-efficiency fluorescent organic light-emitting devices using a phosphorescent sensitizer”, Nature 403, 750 (2000).
[8] H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi, “Highly efficient organic light-emitting diodes from delayed fluorescence”, Nature 492, 234 (2012).
[9] C. W. Tang, “Two‐layer organic photovoltaic cell”, Appl. Phys. Lett. 48, 183 (1986).
[10] G. Yu, J. Gao, J. C. Hummelen, F. Wudl, A. J. Heeger, “Polymer photovoltaic cells: enhanced efficiencies via a network of internal donor-acceptor heterojunctions”, Science 270, 1789 (1995).
[11] J. J. M. Halls, C. A. Walsh, N. C. Greenham, E. A. Marseglia, R. H. Friend, S. C. Moratti, A. B. Holmes, “Efficient photodiodes from interpenetrating polymer networks”, Nature 376, 498 (1995).
[12] C. Adachi, M. A. Baldo, M. E. Thompson, S. R. Forrest, “Nearly 100% internal phosphorescence efficiency in an organic light-emitting device”, J. Appl. Phys. 90, 5048 (2001).
[13] F. B. Dias, K. N. Bourdakos, V. Jankus, K. C. Moss, K. T. Kamtekar, V. Bhalla, J. Santos, M. R. Bryce, A. P. Monkman, “Triplet harvesting with 100% efficiency by way of thermally activated delayed fluorescence in charge transfer OLED emitters”, Adv. Mater. 25, 3707 (2013).
[14] W. Shockley, H. J. Queisser, “Detailed balance limit of efficiency of p‐n Junction solar cells”, J. Appl. Phys. 32, 510 (1961).
[15] D. N. Congreve, J. Lee, N. J. Thompson, E. Hontz, S. R. Yost, P. D. Reusswig, M. E. Bahlke, S. Reineke, T. Van Voorhis, M. A. Baldo, “External quantum efficiency above 100% in a singlet-exciton-fission-based organic photovoltaic cell”, Science 340, 334 (2013).
[16] R. Nagata, H. Nakanotani, W. J. Potscavage, C. Adachi, “Exploiting singlet fission in organic light emitting diodes”, Adv. Mater. 30, 1801484 (2018).
[17] V. Ern, R. E. Merrifield, “Magnetic field effect on triplet exciton quenching in organic crystals”, Phys. Rev. Lett. 21, 609 (1968).
[18] R. E. Merrifield, P. Avakian, R. P. Groff, “Fission of singlet excitons into pairs of triplet excitons in tetracene crystals”, Chem. Phys. Lett. 3, 155 (1969).
[19] M. Pope, C. E. Swenberg, “Electronic processes in organic crystals”, 2nd edition, Oxford university press (1999).
[20] U. E. Steiner, T. Ulrich, “Magnetic field effects in chemical kinetics and related phenomena”, Chem. Rev. 89, 51 (1989).
[21] E. L. Frankevich, A. A. Lymarev, I. Sokolik, F. E. Karasz, S. Blumstengel, H. H. Horhold, “Polaron-pair generation in poly(phenylene vinylenes)”, Phys. Rev. B 46, 9320 (1992).
[22] S. Singh, B. P. Stoicheff, “Double-photon excitation of fluorescence in anthracene single crystals”, J. Chem. Phys. 38, 2032 (1963).
[23] E. L. Frankevich, “On mechanisms of population of spin substates of polaron pairs”, Chem. Phys. 297, 315 (2004).
[24] B. Hu, L. Yan, M. Shao, “Magnetic-field effects in organic semiconducting materials and devices”, Adv. Mater. 21, 1500 (2009).
[25] J. Kalinowski, M. Cocchi, D. Virgili, P. D. Marco, V. Fattori, “Magnetic field effects on emission and current in Alq3-based electroluminescent diodes”, Chem. Phys. Lett. 380, 710 (2003).
[26] Ö. Mermer, G. Veeraraghavan, T. L. Francis, Y. Sheng, D. T. Nguyen, M. Wohlgenannt, A. Köhler, M. K. Al-Suti, M. S. Khan, “Large magnetoresistance in nonmagnetic π–conjugated semiconductor thin film devices”, Phys. Rev. B 72, 205202 (2005).
[27] P. A. Bobbert, T. D. Nguyen, F. W. A. van Oost, B. Koopmans, M. Wohlgenannt, “Bipolaron mechanism for organic magnetoresistance”, Phys. Rev. Lett. 99, 216801 (2007).
[28] N. J. Rolfe, M. Heeney, P. B. Wyatt, A. J. Drew, T. Kreouzis, W. P. Gillin, “Elucidating the role of hyperfine interactions on organic magnetoresistance using deuterated aluminium tris(8-hydroxyquinoline)”, Phys. Rev. B 80, 241201 (2009).
[29] P. Desai, P. Shakya, T. Kreouzis, W. P. Gillin, “The role of magnetic fields on the transport and efficiency of aluminum tris(8-hydroxyquinoline) based organic light emitting diodes”, J. Appl. Phys. 102, 073710 (2007).
[30] J. Y. Song, N. Stingelin, A. J. Drew, T. Kreouzis, W. P. Gillin, “Effect of excited states and applied magnetic fields on the measured hole mobility in an organic semiconductor”, Phys. Rev. B 82, 085205 (2010).
[31] Y. Sheng, T. D. Nguyen, G. Veeraraghavan, Ö. Mermer, M. Wohlgenannt, S. Qiu, U. Scherf, “Hyperfine interaction and magnetoresistance in organic semiconductors”, Phys. Rev. B 74, 045213 (2006).
[32] B. Hu, Y. Wu, “Tuning magnetoresistance between positive and negative values in organic semiconductors”, Nat. Mater. 6, 985 (2007).
[33] X. Qiao, D. Ma, “Nonlinear optoelectronic processes in organic optoelectronic devices:Triplet-triplet annihilation and singlet fission”, Mater. Sci. Eng., R 139, 100519 (2019).
[34] V. K. Thorsmølle, R. D. Averitt, J. Demsar, D. L. Smith, S. Tretiak, R. L. Martin, X. Chi, B. K. Crone, A. P. Ramirez, A. J. Taylor, “Morphology effectively controls singlet-triplet exciton relaxation and charge transport in organic semiconductors”, Phys. Rev. Lett. 102, 017401 (2009).
[35] N. J. Rolfe, M. Heeney, P. B. Wyatt, A. J. Drew, T. Kreouzis, W. P. Gillin, “Elucidating the role of hyperfine interactions on organic magnetoresistance using deuterated aluminium tris(8-hydroxyquinoline)”, Phys. Rev. B 80, 241201 (2009).
[36] P. Janssen, M. Cox, S. H. W. Wouters, M. Kemerink, M. M. Wienk, B. Koopmans, “Tuning organic magnetoresistance in polymer-fullerene blends by controlling spin reaction pathways”, Nat. Commun. 4, 2286 (2013).
[37] M. Segal, M. A. Baldo, R. J. Holmes, S. R. Forrest, Z. G. Soos, “Excitonic singlet-triplet ratios in molecular and polymeric organic materials”, Phys. Rev. B 68, 075211 (2003).
[38] U. E. Steiner, T. Ulrich, “Magnetic field effects in chemical kinetics and related phenomena”, Chem. Rev. 89, 51 (1989).
[39] E. L. Frankevich, “On mechanisms of population of spin substates of polaron pairs”, Chem. Phys. 297, 315 (2004).
[40] B. Hu, L. Yan, M. Shao, “Magnetic-field effects in organic semiconducting materials and devices”, Adv. Mater. 21, 1500 (2009).
[41] Ö. Mermer, G. Veeraraghavan, T. L. Francis, Y. Sheng, D. T. Nguyen, M. Wohlgenannt, A. Köhler, M. K. Al-Suti, M. S. Khan, “Large magnetoresistance in nonmagnetic π–conjugated semiconductor thin film devices”, Phys. Rev. B 72, 205202 (2005).
[42] P. A. Bobbert, T. D. Nguyen, F. W. A. van Oost, B. Koopmans, M. Wohlgenannt, “Bipolaron mechanism for organic magnetoresistance”, Phys. Rev. Lett. 99, 216801 (2007).
[43] P. Desai, P. Shakya, T. Kreouzis, W. P. Gillin, “The role of magnetic fields on the transport and efficiency of aluminum tris(8-hydroxyquinoline) based organic light emitting diodes”, J. Appl. Phys. 102, 073710 (2007).
[44] B. Hu, Y. Wu, “Tuning magnetoresistance between positive and negative values in organic semiconductors”, Nat. Mater. 6,985 (2007).
[45] M. Wohlgenannt, Z. V. Vardeny, “Spin-dependent exction formation rates in π–conjugated materials”, J. Phys. Condens. Matter 15, 83 (2003).
[46] I. V. Tolstov, A. V. Belov, M. G. Kaplunov, I. K. Yakuschenko, N. G. Spitsina, M. M. Triebel, E. L. Frankevich, “On the role of magnetic field spin effect in photoconductivity of composite films of MEH-PPV and nanosized particles of PbS”, J. Lumin. 112, 368 (2005).
[47] Z. H. Xu, B. Hu, “Photovoltaic processes of singlet and triplet excited states in organic solar cells”, Adv. Funct. Mater. 18, 1 (2008).
[48] R. Eisberg, R. Resnick, “Quantum physics of atoms, molecules, solids, nuclei, and particles”, 2nd edition, Wiley press (1985).
[49] W. Helfrich, “Destruction of triplet excitons in anthracene by injected electrons”, Phys. Rev. Lett. 16, 401 (1966).
[50] M. Wittmer, I. Z. Gränacher, “Exciton-charge carrier interactions in the electroluminescence of crystalline anthracene”, J. Chem. Phys. 63, 4187 (1975).
[51] J. Levinson, S. Z. Weisz, A. Cobas, A. Rolón, “Determination of the triplet exciton-trapped electron interaction rate constant in anthracene crystals”, J. Chem. Phys. 52, 2794 (1970).
[52] C. J. Brabec, G. Zerza, G. Cerullo, S. D. Silvestri, S. Luzzati, J. C. Hummelen, S. Sariciftci, “Tracing photoinduced electron transfer process in conjugated polymer/fullerene bulk heterojunctions in real time”, Chem. Phys. Lett. 340, 232 (2001).
[53] W. Wagemans, B. Koopmans, “Spin transport and magnetoresistance in organic semiconductors”, Phys. Status Solidi B 248, 1029 (2011).
[54] Y. Wang, K. S. Tiras, N. J. Harmon, M. Wohlgenannt, M. E. Flatté, “Immense magnetic response of exciplex light emission due to correlated spin-charge dynamics”, Phys. Rev. X 6, 011011 (2016).
[55] T. D. Nguyen, G. H. Markosian, F. Wang, L. Wojcik, X. G. Li, E. Ehrenfreund, Z. V. Vardeny, “Isotope effect in spin response of π-conjugated polymer films and devices”, Nat. Mater. 9, 345 (2010).
[56] M. Ahmadi, Y. C. Hsiao, T. Wu, Q. Liu, W. Qin, B. Hu, “Effect of photogenerated dipoles in the hole transport layer on photovoltaic performance of organic–inorganic perovskite solar cells”, Adv. Energy Mater. 7, 1601575 (2016).
[57] M. Pope, C. E. Swenberg, “Electronic processes in organic crystals and polymers”, Oxford University Press: New York, (1999).
[58] R. E. Merrifield, “Theory of magnetic field effects on the mutual annihilation of triplet excitons”, J. Chem. Phys. 48, 4318 (1968).
[59] H. Rademaker, A. J. Hoff, R. Van Grondelle, L. N. M. Duysens, “Carotenoid triplet yields in normal and deuterated rhodospirillum rubrum”, Biochim. Biophys. Acta, Bioenerg. 592, 240 (1980).
[60] R. H. Austin, G. L. Baker, S. Etemad, R. Thompson, “Magnetic field effects on triplet exciton fission and fusion in a polydiacetylene”, J. Chem. Phys. 90, 6642 (1989).
[61] C. Y. Cheng, N. Chitraningrum, X. M. Chen, T. C. Wen, T. F. Guo, “Magnetic field effect of the singlet fission reaction in tetracene-based diodes”, Org. Electron. 56, 11 (2018).
[62] M. Quaranta, S. M. Borisov, I. Klimant, “Indicators for optical oxygen sensors.” Bioanal Rev. 4, 115 (2012).
[63] C. A. Nelson, N. R. Monahan, X. Y. Zhu, “Exceeding the Shockley–Queisser limit in solar energy conversion”, Energy Environ. Sci. 6, 3508 (2013).
[64] S. R. Yost, J. Lee, M. W. B. Wilson, T. Wu, D. P. McMahon, R. R. Parkhurst, N. J. Thompson, D. N. Congreve, A. Rao, K. Johnson, M. Y. Sfeir, M. G. Bawendi, T. M. Swager, R. H. Friend, M. A. Baldo, T. V. Voorhis, “A transferable model for singlet-fission kinetics”, Nat. Chem. 6, 492 (2014).
[65] K. Lu, C. Zhao, L. Luan, J. Duan, Y. Xie, M. Shaoa, B. Hu, “Exploring the role of spin-triplets and trap states in photovoltaic processes of perovskite solar cells”, J. Mater. Chem. C 6, 5055 (2018).
[66] N. S. Sariciftci, L. Smilowitz, A. J. Heeger, F. Wud, “Photoinduced electron transfer from a conducting polymer to buckminsterfullerene”, Science 27, 1474 (1992).
[67] N. Aggarwal, A. Patnaik, “Dimeric conformation sensitive electronic excited states of tetracene congeners and their unconventional non-fluorescent behaviour”, J. Chem. Sci. 52, 131 (2019).