Ammonia borane all‑in‑one modification strategy enables high‑performance perovskite solar cells

As perovskite photovoltaics edge toward gigawatt production, buried SnO₂/perovskite defects and iodine-volatilization losses still cap industrial yield. Now, researchers from Beijing National Laboratory for Molecular Sciences, CAS, led by Prof. Jizheng Wang, report a single-molecule “all-in-one” additive—ammonia borane (BNH₆)—that is spin-coated on both the electron-transport and hole-transport sides of the perovskite layer during normal processing. Published in Nano-Micro Letters, the treatment lifts certified efficiency to 25.98 % and retains 90 % of that value after 500 h continuous illumination without encapsulation.

Why BNH₆ All-in-One Matters

• Dual-Interface Healing: 30 % of BNH₆ hydrolyses to BO₂⁻ that plugs SnO₂ oxygen vacancies, while intact B–N units coordinate under-coordinated Pb²⁺ and donate electrons to reduce I⁰ back to I⁻, shutting two major recombination channels in one step.
• Stress & Crystallization Control: Delays crystal growth, enlarges grains (1.59 → 2.26 µm) and releases tensile residual stress from 43.7 to 4.3 MPa, suppressing crack initiation under thermal cycling.
• Energy-Level Realignment: Lowers SnO₂ work function (4.50 → 4.40 eV) and upshifts perovskite valence band, improving electron extraction and hole blocking without extra buffer layers.

Innovative Design & Features

• Single-Step Compatibility: One 1 mg mL^-1 aqueous or IPA solution replaces conventional multi-molecule cocktails; full process carried out in ambient air (< 30 % RH) and fits existing roll-to-roll coaters.
• In-Situ Diagnostics: XPS, UPS, LEIPS, ToF-SIMS and GIXRD verify BO₂⁻ occupancy of O-vac, Pb–N coordination and stress release throughout the 500 nm-thick film depth.
• Carrier Dynamics: Time-resolved PL and fs-TAS show lifetime lengthening to 9.1 µs and trap density falling ~40 %, corroborating suppressed non-radiative recombination.

Applications & Future Outlook

• Record Metrics: Champion cell yields 26.43 % in-house (25.98 % certified by IEE, CAS) with negligible J–V hysteresis; EQE-integrated Jsc of 25.36 mA cm^-2 matches J–V value within 3 %.
• Triple ISOS Durability: Unencapsulated devices retain 84 % PCE after 800 h @ 65 °C (ISOS-T-1), 93 % after 500 h LED (ISOS-L-1) and 96 % after 500 h 50 % RH ambient air (ISOS-D-1).

Manufacturing Edge: Process eliminates separate interface treatments, cutting coating steps by 30 % and offering an immediate drop-in upgrade for gigawatt-scale perovskite production lines.