@article{yonemoto_papa_sheykhi_castellano_2021, title={Controlling Thermally Activated Delayed Photoluminescence in CdSe Quantum Dots through Triplet Acceptor Surface Coverage}, volume={12}, ISSN={["1948-7185"]}, url={https://doi.org/10.1021/acs.jpclett.1c00746}, DOI={10.1021/acs.jpclett.1c00746}, abstractNote={Quantum-dot/molecule composites (QD/mol) have demonstrated useful photochemical properties for many photonic and optoelectronic applications; however, a comprehensive understanding of these materials remains elusive. This work introduces a series of cadmium(II) selenide/1-pyrenecarboxylic acid (CdSe/PCA) nanomaterials featuring bespoke PCA surface coverage on CdSe585 (coded by the peak of the first exciton absorption band) to glean insight into the QD/mol photophysical behavior. Tailoring the energy gap between the CdSe585 first exciton band (2.1 eV) and the lowest PCA triplet level (T1 = 2.0 eV) to be nearly isoenergetic, strong thermally activated delayed photoluminescence (TADPL) is observed resulting from reverse triplet-triplet energy transfer. The resultant average decay time constant (τobs) of the photoluminescence emanating from CdSe585 is deterministically controlled with surface-bound PCAn chromophores (n = average number of adsorbed PCA molecules) by shifting the triplet excited state equilibrium from the CdSe585 to the PCA molecular triplet reservoir as a function of n.}, number={15}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, publisher={American Chemical Society (ACS)}, author={Yonemoto, Daniel T. and Papa, Christopher M. and Sheykhi, Sara and Castellano, Felix N.}, year={2021}, month={Apr}, pages={3718–3723} }
 @article{wells_yarnell_palmer_lee_papa_castellano_2020, title={Energy Migration Processes in Re(I) MLCT Complexes Featuring a Chromophoric Ancillary Ligand}, volume={59}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/acs.inorgchem.0c00644}, DOI={10.1021/acs.inorgchem.0c00644}, abstractNote={We present the synthesis, structural characterization, electronic structure calculations, and ultrafast and supra-nanosecond photophysical properties of a series of five Re(I) bichromophores exhibiting metal to ligand charge transfer (MLCT) excited states based on the general formula fac-[Re(N∧N)(CO)3(PNI-py)]PF6, where PNI-py is 4-piperidinyl-1,8-naphthalimidepyridine and N∧N is a diimine ligand (Re1–5), along with their corresponding model chromophores where 4-ethylpyridine was substituted for PNI-py (Mod1–5). The diimine ligands used include 1,10-phenanthroline (phen, 1), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bcp, 2), 4,4′-di-tert-butyl-2,2′-bipyridine (dtbb, 3), 4,4′-diethyl ester-2,2′-bipyridine (deeb, 4), and 2,2′-biquinoline (biq, 5). In these metal–organic bichromophores, structural modification of the diimine ligand resulted in substantial changes to the observed energy transfer efficiencies between the two chromophores as a result of the variation in 3MLCT excited-state energies. The photophysical properties and energetic pathways of the model chromophores were investigated in parallel to accurately track the changes that arose from introduction of the organic chromophore pendant on the ancillary ligand. All relevant photophysical and energy transfer processes were probed and characterized using time-resolved photoluminescence spectroscopy, ultrafast and nanosecond transient absorption spectroscopy, and time-dependent density functional theory calculations. Of the five bichromophores in this study, four (Re1–4) exhibited a thermal equilibrium between the 3PNI-py and the 3MLCT excited state, drastically extending the lifetimes of the parent model chromophores.}, number={12}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Wells, Kaylee A. and Yarnell, James E. and Palmer, Jonathan R. and Lee, Tia S. and Papa, Christopher M. and Castellano, Felix N.}, year={2020}, month={Jun}, pages={8259–8271} }
 @article{papa_garakyaraghi_granger_anthony_castellano_2020, title={TIPS-pentacene triplet exciton generation on PbS quantum dots results from indirect sensitization}, volume={11}, ISSN={2041-6520 2041-6539}, url={http://dx.doi.org/10.1039/d0sc00310g}, DOI={10.1039/d0sc00310g}, abstractNote={Many fundamental questions remain in the elucidation of energy migration mechanisms across the interface between semiconductor nanomaterials and molecular chromophores.}, number={22}, journal={Chemical Science}, publisher={Royal Society of Chemistry (RSC)}, author={Papa, Christopher M. and Garakyaraghi, Sofia and Granger, Devin B. and Anthony, John E. and Castellano, Felix N.}, year={2020}, pages={5690–5696} }
 @article{yonemoto_papa_mongin_castellano_2020, title={Thermally Activated Delayed Photoluminescence: Deterministic Control of Excited-State Decay}, volume={142}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/jacs.0c03331}, DOI={10.1021/jacs.0c03331}, abstractNote={Thermally activated photophysical processes are ubiquitous in numerous organic and metal-organic molecules, leading to chromophores with excited state properties that can be considered an equilibrium mixture of the available low-lying states. Relative populations of the equilibrated states are governed by temperature. Such molecules have been devised as high quantum yield emitters in modern organic light-emitting diode technology and for deterministic excited state lifetime control to enhance chemical reactivity in solar energy conversion and photocatalytic schemes. The recent discovery of thermally activated photophysics at CdSe nanocrystal-molecule interfaces enables a new paradigm wherein molecule-quantum dot constructs are used to systematically generate material with predetermined photophysical response and excited state properties. Semiconductor nanomaterials feature size-tunable energy level engineering, which considerably expands the purview of thermally activated photophysics beyond what is possible using only molecules. This Perspective is intended to provide a non-exhaustive overview of the advances that led to the integration of semiconductor quantum dots in thermally activated delayed photoluminescence (TADPL) schemes and to identify important challenges moving into the future. The initial establishment of excited state lifetime extension utilizing triplet-triplet excited-state equilibria is detailed. Next, advances involving the rational design of molecules composed of both metal-containing and organic-based chromophores that produce the desired TADPL are described. Finally, the recent introduction of semiconductor nanomaterials into hybrid TADPL constructs is discussed, paving the way towards the realization of fine-tuned deterministic excited state lifetime control. It is envisioned that libraries of synthetically facile composites will be broadly deployed as photosensitizers and light emitters for numerous synthetic and optoelectronic applications in the near future.}, number={25}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Yonemoto, Daniel T. and Papa, Christopher M. and Mongin, Cedric and Castellano, Felix N.}, year={2020}, month={Jun}, pages={10883–10893} }
 @article{salehi_dong_shin_zhu_papa_thy bui_castellano_so_2019, title={Realization of high-efficiency fluorescent organic light-emitting diodes with low driving voltage}, volume={10}, ISSN={2041-1723}, url={http://dx.doi.org/10.1038/s41467-019-10260-7}, DOI={10.1038/s41467-019-10260-7}, abstractNote={Abstract}, number={1}, journal={Nature Communications}, publisher={Springer Science and Business Media LLC}, author={Salehi, Amin and Dong, Chen and Shin, Dong-Hun and Zhu, Liping and Papa, Christopher and Thy Bui, Anh and Castellano, Felix N. and So, Franky}, year={2019}, month={May} }
 @article{chen_liu_guo_peng_garakyaraghi_papa_castellano_zhao_ma_2018, title={Energy Transfer Dynamics in Triplet–Triplet Annihilation Upconversion Using a Bichromophoric Heavy-Atom-Free Sensitizer}, volume={122}, ISSN={1089-5639 1520-5215}, url={http://dx.doi.org/10.1021/acs.jpca.8b05901}, DOI={10.1021/acs.jpca.8b05901}, abstractNote={A heavy-atom-free triplet sensitizer suitable for triplet-triplet annihilation-based photon upconversion was developed from the thermally activated delayed fluorescence (TADF) molecule 4CzPN by covalently tethering a pyrene derivative (DBP) as a triplet acceptor. The triplet exciton produced by 4CzPN is captured by the intramolecular pyrenyl acceptor and subsequently transferred via intermolecular triplet-triplet energy transfer (TTET) to freely diffusing pyrenyl acceptors in toluene. Transient absorption and time-resolved photoluminescence spectroscopy were employed to examine the dynamics of both the intra- and intermolecular TTET processes, and the results indicate that the intramolecular energy transfer from 4CzPN to DBP is swift, quantitative, and nearly irreversible. The reverse intersystem crossing is suppressed while intersystem crossing remains efficient, achieving high triplet yield and long triplet lifetime simultaneously. The ultralong excited state lifetime characteristic of the DBP triplet was shown to be crucial for enhancing the intermolecular TTET efficiency and the subsequent triplet-triplet annihilation photochemistry. It was also demonstrated that with the long triplet lifetime of the tethered DBP, TTET was enabled under low free acceptor concentrations and/or with sluggish molecular diffusion in polymer matrixes.}, number={33}, journal={The Journal of Physical Chemistry A}, publisher={American Chemical Society (ACS)}, author={Chen, Qi and Liu, Yiming and Guo, Xinyan and Peng, Jiang and Garakyaraghi, Sofia and Papa, Christopher M. and Castellano, Felix N. and Zhao, Dahui and Ma, Yuguo}, year={2018}, month={Jul}, pages={6673–6682} }
 @article{wang_deloach_jiang_papa_myahkostupov_castellano_liu_dougherty_2017, title={Tuning interfacial spin filters from metallic to resistive within a single organic semiconductor family}, volume={95}, ISSN={2469-9950 2469-9969}, url={http://dx.doi.org/10.1103/PhysRevB.95.241410}, DOI={10.1103/physrevb.95.241410}, abstractNote={Jingying Wang,1 Andrew Deloach,1 Wei Jiang,2 Christopher M. Papa,3 Mykhaylo Myahkostupov,3 Felix N. Castellano,3 Feng Liu,2 and Daniel B. Dougherty1,* 1Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202, USA 2Department of Material Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA 3Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA (Received 6 January 2017; revised manuscript received 26 May 2017; published 30 June 2017)}, number={24}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Wang, Jingying and Deloach, Andrew and Jiang, Wei and Papa, Christopher M. and Myahkostupov, Mykhaylo and Castellano, Felix N. and Liu, Feng and Dougherty, Daniel B.}, year={2017}, month={Jun} }