Lukas Naimovičius

Vilnius University

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Karolis Kazlauskas

Vilnius University

Edvinas Radiunas

Vilnius University

Edvinas Orentas

Vilnius University

Paulius Baronas

Vilnius University

Augustina Jozeliūnaitė

Vilnius University

Saulius Juršėnas

Vilnius University

Andrew B. Pun

University of California, San Diego

Pankaj Bharmoria

Instituto de Ciencia de Materiales de Sevilla

Gediminas Kreiza

Vilnius University

Kasper Moth‐Poulsen

Institució Catalana de Recerca i Estudis Avançats

Cooperative Institutions

Vilnius University

Instituto de Ciencia de Materiales de Sevilla

Institut de Ciència de Materials de Barcelona

Institute of Nanotechnology

Applied Research (United States)

Center for Physical Sciences and Technology

Centre de Géosciences

University of California, San Diego

ETH Zurich

Chalmers University of Technology

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NIR-to-vis photon upconversion in rubrenes with increasing structural complexity

Journal of Materials Chemistry C (2021)

Edvinas Radiunas Manvydas Dapkevičius Lukas Naimovičius Paulius Baronas Steponas Raišys

Peripheral linking of rubrene emitters is found to deliver enhanced TTA efficiency vs. core linking. This provides valuable insight for their rational modification towards improved NIR-to-vis photon upconversion efficiency in the solid state.

Photon Upconversion

Rubrene

10.1039/d1tc00296a

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Citations (13)

Cyano-substituted rubrene compounds for NIR-to-visible photon upconversion

Lukas Naimovičius Edvinas Radiunas Augustina Jozeliūnaitė Edvinas Orentas Karolis Kazlauskas

Rubrene

Photon Upconversion

10.1117/12.2621183

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The statistical probability factor in triplet mediated photon upconversion: a case study with perylene

Journal of Materials Chemistry C (2023)

Lukas Naimovičius Edvinas Radiunas Manvydas Dapkevičius Pankaj Bharmoria Kasper Moth‐Poulsen

Triplet-triplet annihilation photon upconversion (TTA-UC) is a process where two low-energy photons are converted into one higher-energy photon. A crucial component for an efficient upconversion process is the statistical probability factor (f), defined as the probability of the formation of a high-energy singlet state upon coupling of two low-energy triplet states. Theoretically, f depends on the energy level distribution, molecular orientation, inter-triplet exchange coupling of triplet dyads, and spin-mixing of resulting spin states (singlet, triplet, and quintet). However, experimental values of f for acene-based annihilators have been subject to large variations due to many factors that have resulted in the reporting of different f values for the same molecule. In this work, we discuss these factors by studying perylene as a case study annihilator, for which by far the largest variation in f = 16 to 100% has been reported. We systematically investigated the TTA-UC of PdTPBP:perylene, as a sensitizer-annihilator pair and obtained the experimental f = 17.9 ± 2.1% for perylene in THF solution. This limits the maximum TTA-UC quantum yield to 9.0% (out of 50%) for this annihilator. We found that such a low f value for perylene is largely governed by the energy-gap law where higher non-radiative losses due to the small energy gap between 2 × T1 and T2 affect the probability of singlet formation. Interestingly, we found this observation true for other acene-based annihilators whose emission ranges from the UV to the yellow region, thus providing a blueprint for future design of efficient TTA-UC systems.

Photon Upconversion

Singlet fission

10.1039/d3tc03158f

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Citations (9)

CCDC 2169522: Experimental Crystal Structure Determination

The Cambridge Structural Database (2022)

Paulius Baronas Gediminas Kreiza Lukas Naimovičius Edvinas Radiunas Karolis Kazlauskas

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

10.5517/ccdc.csd.cc2btklb

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CCDC 2170150: Experimental Crystal Structure Determination

The Cambridge Structural Database (2022)

Paulius Baronas Gediminas Kreiza Lukas Naimovičius Edvinas Radiunas Karolis Kazlauskas

10.5517/ccdc.csd.cc2bv6v8

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Impact of Steric Effects on the Statistical Probability Factor in Triplet-Triplet Annihilation Upconversion

Journal of Materials Chemistry C (2024)

Lukas Naimovičius Simon K. Zhang Andrew B. Pun

The statistical probability factor (f) in triplet-triplet annihilation (TTA) upconversion (UC) is one of the key elements governing UC performance. This factor indicates the probability that an emissive singlet state...

Annihilation

Photon Upconversion

10.1039/d4tc03269a

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Citations (1)

Optimizing Upconversion Quantum Yield via Structural Tuning of Dipyrrolonaphthyridinedione Annihilators

Angewandte Chemie (2024)

Alexandra J. Lyons Lukas Naimovičius Simon K. Zhang Andrew B. Pun

Abstract Triplet‐triplet annihilation upconversion (TTA‐UC) is a photophysical process in which two low‐energy photons are converted into one higher‐energy photon. This type of upconversion requires two species: a sensitizer that absorbs low‐energy light and transfers its energy to an annihilator, which emits higher‐energy light after TTA. In spite of the multitude of applications of TTA‐UC, few families of annihilators have been explored. In this work, we show dipyrrolonaphthyridinediones (DPNDs) can act as annihilators in TTA‐UC. We found that structural changes to DPND dramatically increase its upconversion quantum yield (UCQY). Our optimized DPND annihilator demonstrates a high maximum internal UCQY of 9.4 %, outperforming the UCQY of commonly used near‐infrared‐to‐visible annihilator rubrene by almost double.

Photon Upconversion

Quantum yield

10.1002/ange.202411003

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Sweet Spot of Intermolecular Coupling in Crystalline Rubrene: Intermolecular Separation to Minimize Singlet Fission and Retain Triplet–Triplet Annihilation

The Journal of Physical Chemistry C (2022)

Paulius Baronas Gediminas Kreiza Lukas Naimovičius Edvinas Radiunas Karolis Kazlauskas

Singlet fission is detrimental to NIR-to-vis photon upconversion in the solid rubrene (Rub) films, as it diminishes photoluminescence efficiency. Previous studies have shown that thermally activated triplet energy transport drives singlet fission with nearly 100% efficiency in closely packed Rub crystals. Here, we examine triplet separation and recombination as a function of intermolecular distance in the crystalline films of Rub and the t-butyl substituted rubrene (tBRub) derivative. The increased intermolecular distance and altered molecular packing in tBRub films cause suppressed singlet dissociation into free triplets due to slower triplet energy transport. It was found that the formation of correlated triplet pairs 1(TT) and partial triplet separation 1(T···T) occurs in both Rub and tBRub films despite differences in intermolecular coupling. Under weak intermolecular coupling as in tBRub, geminate triplet annihilation of 1(T···T) outcompetes dissociation into free triplets, resulting in emission from the 1(TT) state. Essentially, increasing intermolecular distance up to a certain point (a sweet spot) is a good strategy for suppressing singlet fission and retaining triplet–triplet annihilation properties.

Singlet fission

Rubrene

Annihilation

10.1021/acs.jpcc.2c04572

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Citations (14)

Triplet-Triplet Annihilation Mediated Photon Upconversion Solar Energy Systems

Materials Chemistry Frontiers (2023)

Lukas Naimovičius Pankaj Bharmoria Kasper Moth‐Poulsen

Triplet–triplet annihilation mediated solar energy harvesting systems for a global transition toward carbon-neutral energy technologies.

Annihilation

Photon Upconversion

10.1039/d3qm00069a

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Citations (32)

CN‐Tuning: A Pathway to Suppress Singlet Fission and Amplify Triplet‐Triplet Annihilation Upconversion in Rubrene

Advanced Optical Materials (2025)

Edvinas Radiunas Lukas Naimovičius Paulius Baronas Augustina Jozeliūnaitė Edvinas Orentas

Abstract Incoherent photon upconversion (UC) mediated by triplet‐triplet annihilation (TTA) offers multiple implementation pathways, from bio‐related applications to energy harvesting in photovoltaics. Despite its potential, TTA‐UC efficiency in the near‐infrared (NIR) range is notably low, particularly in solid‐state systems. Rubrene ( Rub ), a key annihilator in this spectral range, faces significant concentration quenching, primarily due to singlet fission (SF). To mitigate this issue, herein, the cyano (CN) functionalization of Rub is explored to reduce SF and boost solid‐state UC performance. By systematically increasing the number of CN groups, the modified Rub is examined in both solution and solid‐state environments, benchmarking it against unmodified Rub and assessing each energy transfer step. The findings reveal that CN modification, while detrimental to UC efficiency in solution, markedly improves solid‐state UC performance. Specifically, Rub functionalized with two peripheral CN groups achieves a UC quantum yield (Φ UC ) of 3.0% (out of a theoretical maximum of 50%) in the solid‐state–nearly tripling the maximum yield achieved with unmodified Rub . This advancement not only presents a more efficient and stable alternative to conventional Rub annihilators but also highlights the potential of CN‐tuning for enhancing other NIR annihilators in the solid state.

Rubrene

Photon Upconversion

Singlet fission

Annihilation

10.1002/adom.202403032

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