title: Understanding the Control of Singlet-Triplet Splitting for Organic Exciton Manipulating: A Combined Theoretical and Experimental Approach.
abstract: Developing organic optoelectronic materials with desired photophysical properties has always been at the forefront of organic electronics. The variation of singlet-triplet splitting (ΔEST) can provide useful means in modulating organic excitons for diversified photophysical phenomena, but controlling ΔEST in a desired manner within a large tuning scope remains a daunting challenge. Here, we demonstrate a convenient and quantitative approach to relate ΔEST to the frontier orbital overlap and separation distance via a set of newly developed parameters using natural transition orbital analysis to consider whole pictures of electron transitions for both the lowest singlet (S1) and triplet (T1) excited states. These critical parameters revealed that both separated S1 and T1 states leads to ultralow ΔEST; separated S1 and overlapped T1 states results in small ΔEST; and both overlapped S1 and T1 states induces large ΔEST. Importantly, we realized a widely-tuned ΔEST in a range from ultralow (0.0003 eV) to extra-large (1.47 eV) via a subtle symmetric control of triazine molecules, based on time-dependent density functional theory calculations combined with experimental explorations. These findings provide keen insights into ΔEST control for feasible excited state tuning, offering valuable guidelines for the construction of molecules with desired optoelectronic properties.
authors.affiliation: Key Laboratory for Organic Electronics and Information Displays &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts &Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Chen
authors.affiliation: Key Laboratory for Organic Electronics and Information Displays &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts &Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Key Laboratory for Organic Electronics and Information Displays &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts &Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Yuan
authors.affiliation: 1] Key Laboratory for Organic Electronics and Information Displays &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts &Telecommunications, 9 Wenyuan Road, Nanjing 210023, China [2] Key Laboratory of Flexible Electronics &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, China.
authors.forename: Zhongfu
authors.initials: Z
authors.lastname: An
authors.affiliation: Key Laboratory for Organic Electronics and Information Displays &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts &Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
authors.forename: Runfeng
authors.initials: R
authors.lastname: Chen
authors.affiliation: Key Laboratory for Organic Electronics and Information Displays &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts &Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Tao
authors.affiliation: Key Laboratory for Organic Electronics and Information Displays &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts &Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
authors.forename: Huanhuan
authors.initials: H
authors.lastname: Li
authors.affiliation: Key Laboratory of Flexible Electronics &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, China.
authors.forename: Xiaoji
authors.initials: X
authors.lastname: Xie
authors.affiliation: 1] Key Laboratory for Organic Electronics and Information Displays &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts &Telecommunications, 9 Wenyuan Road, Nanjing 210023, China [2] Key Laboratory of Flexible Electronics &Institute of Advanced Materials, Jiangsu National Synergistic Innovation Center for Advanced Materials, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang