The approach uses pi-conjugation extension of triphenylamine-based semiconducting ligands. Two new ligands were designed - N-TPEAI (fused-ring) and P-TPEAI (covalently-linked) - with structural similarities to the PTAA backbone itself. Density functional theory calculations reveal that P-TPEAI's flexible biphenyl tail enables parallel-displaced pi-pi stacking with multiple charge channels, achieving larger binding energies (-16.42 eV) and hole-transfer integrals (118.8 meV) than its fused-ring counterpart. This enhanced intermolecular coupling strengthens interactions both within the 2D perovskite layers and at the perovskite/PTAA interface, creating synergistic pathways for hole transport.
The optimized 2D/3D PSCs deliver a champion efficiency of 26.13% - the highest reported for PTAA-based devices - with an open-circuit voltage of 1.201 V and a fill factor of 83.96%. Transient photocurrent decay accelerates from 3.82 microseconds to 1.32 microseconds, while Mott-Schottky analysis confirms reduced non-radiative recombination.
Stability performance is equally strong. Unencapsulated devices retained 84.9% of initial performance after 1,000 hours under the ISOS-L-2 light-heat stress protocol, demonstrating exceptional resistance to the conditions that typically degrade perovskite devices in real-world deployment.
The work establishes molecular engineering guidelines for organic spacer design in PSCs, with broad applicability expected in inverted architectures and tandem cell configurations. The results are published in the journal Nano-Micro Letters.
Research Report:Interfacial Coupling Design Enhancing Hole Transport in PTAA-Based Perovskite Solar Cells with Efficiency over 26%
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