Browsing by Author "Poudel, B."

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    A Molecular-Level Exploration of Dopant-Free Pyrazine-Derived Hole Transport Materials: Investigation of Interfacial Interaction in Perovskite Photovoltaics
    (John Wiley and Sons Inc, 2025) Sheshachala, A.; Keremane, K.S.; Bhat, V.G.; Karunakar Shankar, S.; Asuo, I.M.; Doumon, N.Y.; Poudel, B.; Udayakumar, U.
    The development of innovative core structures and peripheral groups for organic hole-transporting materials (HTMs) continues to be a focal point in enhancing the performance of perovskite solar cells (PVSCs). This study reports the design and synthesis of dopant-free pyrazine-based HTMs. PS1 features a D–A–D type structure with pyrazine as the acceptor and 4,4?-dimethoxy triphenylamine (4,4?-OMe-TPA) as the donor, while PS2 adopts a D–?–A–?–D configuration with an additional thiophene unit as ?-spacer along with 4,4?-OMe-TPA as donor. Both compounds are synthesized through a simple two-step synthetic procedure. These HTMs are subjected to structural, photophysical, electrochemical, theoretical, and photoelectrochemical studies with an emphasis on evaluation of structure–property relationships. Theoretical studies are conducted to explore the electronic distribution, optimized molecular structure, and frontier molecular orbitals. Their performance in PVSCs is systematically evaluated without adding dopants. PS2 exhibits superior photoluminescence quenching compared to PS1, indicating more efficient charge transfer from the perovskite layer. Notably, PS2 achieves a power conversion efficiency (PCE) of 11.9%, surpassing the performance of PS1 (PCE of 10.15%). These findings highlight the potential of adjusting the electron-deficient core and ?-bridge units as an effective strategy to optimize the properties of HTMs and improve their performance in PVSC applications. © 2025 Wiley-VCH GmbH.
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    Dopant-free hydrophobic fluorene-based hole transport materials: impact of methoxy-substituted triphenylamine and carbazole peripheral groups on the performance of perovskite solar cells
    (Royal Society of Chemistry, 2025) Bhat, V.G.; Keremane, K.S.; Subramanya, K.S.; Archana, S.; Hegde, A.; Asuo, I.M.; Poudel, B.; Udayakumar, U.
    Hole-transporting materials (HTMs) are crucial for charge separation in perovskite solar cells (PVSCs). Besides possessing suitable HOMO/LUMO energies, HTMs should ideally be hydrophobic to protect the perovskites from atmospheric moisture to enhance device stability. We designed two fluorene-core D-?-D-type organic HTMs (V1 and V2), consisting of either 4,4?-methoxy triphenylamine (V1) or N-phenyl-3,6-methoxy carbazole (V2) as the peripheral donor moiety. Optoelectronic characterization and density functional theory calculations confirmed the intramolecular charge transfer within these new HTMs. UPS and REELS analyses revealed favorable HOMO-LUMO energy level alignment of V1 and V2 with the work functions of MAPbI3 and gold electrode for effective charge extraction. TRPL and transient absorption studies commendably explained better quenching of perovskite's luminescence by V1 over V2, suggesting a better interfacial contact of V1 with the perovskite layer. Accordingly, the PVSCs with V1 and V2 as HTMs in an architecture ITO/SnO2/MAPbI3/HTM(V1 or V2)/Au demonstrated power conversion efficiency (PCE) of 14.05% and 12.73% respectively. Also, the device with V1 retains 75% of its initial efficiency for more than 480 hours. The contact angle measurements revealed the strong hydrophobicity of both alkylated fluorene molecules (V1 and V2), and impedance spectroscopy measurements further revealed higher Rrec values for these HTMs, indicating improved charge transport and reduced recombination losses. These findings demonstrate the potential of the newly developed hydrophobic fluorene-based HTMs for achieving long-lasting performance in PVSCs. © 2025 The Royal Society of Chemistry.