Constructing Multiresonance Thermally Activated Delayed Fluorescence Emitters for Organic LEDs: A Computational Investigation

In organic light-emitting diodes (OLEDs), the pursuit of efficient molecular emitters has led to the development of thermally activated delayed fluorescence (TADF) molecules. While TADF compounds have promising properties, they face challenges such as energy gap constraints and uphill exciton transfer. Inverted emitters (INVEST) offer a novel solution with an inverted singlet−triplet energy (ΔE ST ) gap, enabling efficient utilization of excitons. This study examines the design and computational analysis of an array of molecules, including 23 INVEST emitters and remaining with positive energy gaps. Within the STEOM-DLPNO−CCSD framework, we explore the role of various molecular fragments in determining ΔE ST . We also assess the importance of dynamic spin-polarization (DSP) obtained via the Pariser−Parr−Pople (PPP) scheme in energy gap determination. Exciting trends emerged from our results, with pentalenecontaining compounds consistently manifesting negative ΔE ST values while their naphthalene counterparts exhibited contrasting behavior. Moreover, we observed a negative DSP correlates with inverted singlet−triplet gaps. Overall, this research advances OLED materials through molecular design and computational analysis, offering avenues for optimizing exciton management and enhancing device performance.

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Modeling MR-TADF Emitters: Excited-State Decay Rate Constants and Wave Function Descriptors

T. do Casal,

Badawy,

Escudero

2024

J. Phys. Chem. C

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Multiresonance thermally activated delayed fluorescence (MR-TADF) emitters have gained popularity given their potential of attaining negligible singlet−triplet energy gaps, i.e., ΔE ST , without hindering emission, thus increasing the reverse and direct intersystem crossing rates without affecting fluorescence. This is achieved due to the singlet and triplet states' short-range charge transfer character (SRCT). Thus, obtaining quantitative information about SRCT would help develop new MR-TADF emitters. This work studies three different families of MR-TADF emitters: DOBOA, DiKTa, and OQAO. First, we compute their adiabatic ΔE ST with four different methods (TDA-CAM-B3LYP, STEOM-DLPNO-CCSD, ADC(2), and SCS-CC2). Then, we compute fluorescence (k r ), direct (k ISC ), and reverse intersystem crossing rate constants. For k r , we assessed the effect of different levels of approximations on the rate calculations. We show that k r does not depend significantly on the different harmonic models (adiabatic Hessian or vertical Hessian), coordinate systems, and broadening widths. Moreover, Herzberg−Teller effects are negligible for k r but are the main contribution for k ISC and k RISC . The computed rate constants agree well with the experimental results. Moreover, we propose the use of two wave function descriptors, Q a t and LOC a , based on the 1-particle transition density matrix, which assigns the amount of charge centered on the atoms. We compute these descriptors for three transitions: S

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Constructing Multiresonance Thermally Activated Delayed Fluorescence Emitters for Organic LEDs: A Computational Investigation

Cited by 5 publications

References 66 publications

Sunlight induced C-H arylation of aromatic heterocycles: First example of A3 and A2B type corroles as photoredox catalysts

Sunlight induced C-H arylation of aromatic heterocycles: First example of A3 and A2B type corroles as photoredox catalysts

Rational Design of Organic Emitters with Inverted Singlet–Triplet Gaps for Enhanced Exciton Management

Modeling MR-TADF Emitters: Excited-State Decay Rate Constants and Wave Function Descriptors

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