Interfacial coupling design enhancing hole transport in PTAA‑based perovskite solar cells with efficiency over 26%

As the quest for high-efficiency, stable perovskite solar cells (PSCs) intensifies, the challenge of carrier transport at 2D/3D heterojunctions remains a critical bottleneck. Now, researchers from Dalian University of Technology, Fudan University, and City University of Hong Kong, led by Professor Ze Yu, Professor Yingguo Yang, and Professor Hin-Lap Yip, have unveiled a breakthrough molecular design strategy that pushes PTAA-based PSCs beyond 26% efficiency.

Why This Interface Matters

Conventional 2D/3D perovskite heterojunctions suffer from quantum well effects that hinder hole extraction, while structural mismatches at the perovskite/PTAA interface create additional transport barriers. The team addresses both issues simultaneously through π-conjugation extension of triphenylamine-based semiconducting ligands—designing N-TPEAI (fused-ring) and P-TPEAI (covalently-linked) to mirror the backbone of PTAA itself.

Innovative Design and Mechanism

Density functional theory reveals that P-TPEAI's flexible biphenyl tail enables parallel-displaced π-π stacking with multifarious 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 2D perovskites and at the perovskite/PTAA interface, creating synergistic pathways for hole transport.

Outstanding Performance

The optimized 2D/3D PSCs deliver a champion efficiency of 26.13%—the highest reported for PTAA-based devices—with open-circuit voltage of 1.201 V and fill factor of 83.96%. Transient photocurrent decay accelerates from 3.82 μs to 1.32 μs, while Mott-Schottky analysis confirms reduced non-radiative recombination. Crucially, unencapsulated devices retain 84.9% of initial performance after 1,000 hours under ISOS-L-2 protocol, demonstrating exceptional light-heat stability.

Future Outlook

This work establishes molecular engineering guidelines for organic spacer design, opening avenues for next-generation high-efficiency PSCs with commercial-grade stability. The PTAA-compatible strategy promises broad applicability in inverted architectures and tandem configurations.

Stay tuned for more innovations from this collaborative team!