LONGi Hits 33.35% on Flexible Perovskite–Silicon Tandems — Why It Matters Now

Headline news: LONGi has achieved 33.35% efficiency on a flexible perovskite–silicon tandem cell (≈1 cm²), certified by NREL. On an M6 wafer–sized flexible device, the company reports 29.8% efficiency, validated by Fraunhofer ISE. The work uses a dual-buffer strategy to improve adhesion and charge extraction in bendable stacks.

What actually happened (in plain English)

• The team built a tandem cell on a 60 µm silicon wafer that can fold to a 15 mm bend radius, yet still hit 33.35% under standard test conditions; the large flexible device reached 29.8% and retained ~97% of its initial performance after extensive bending and thermal cycling, per the report.

• The underlying dual SnOx buffer approach is described in the associated Nature article, which details how the layers mitigate sputtering damage and delamination at critical interfaces in flexible tandems.
• Context: earlier in 2025, LONGi also announced a 34.85% record for a rigid, two-terminal perovskite–silicon tandem (NREL-certified), underscoring the wider momentum in tandems

Why flexible tandems matter

1. New rooftops become viable
   Lightweight, bendable cells can open solar to structures that struggle with glass module weight or flat-panel geometry (domed canopies, curved façades, retrofits). Expect the earliest wins in BIPV and low-load roofs.

2. Less balance-of-system (BoS) per MW
   Higher efficiency + lower mass can reduce rails, fasteners, and labor per installed kWp—especially valuable where roof real estate or load limits are tight. (Industry trend tied to rising tandem efficiencies.)
3. A bridge to next-gen products
   As tandem research translates from rigid to flexible form factors, buyers get more form-factor choice without giving up high conversion efficiency.

The fine print (what to watch)

• Commercial readiness vs. lab records: Certification validates devices, not yet 25-year bankability. Procurement teams should track pilot deployments and encapsulation durability before large-scale adoption.

• Mechanical & moisture stress: Flexible stacks must survive bending cycles, humidity-freeze, and ion-migration over time—areas the new dual-buffer approach is meant to reinforce, per the Nature paper.

12–24 month outlook

• Pilot products first: Expect niche, lightweight/BIPV trials while mainstream rooftop and utility projects continue using today’s bankable TOPCon/HJT/back-contact modules.

• String design will evolve: As tandem Voc/I–V profiles change, string sizing, MPPT windows, and DC/AC ratios will get updates in future inverter specs. (Track this in datasheets/firmware notes.)

What buyers should do now

• Build current projects with proven tech to capture savings today; keep an option lane for future tandem upgrades.

• Specify wide-window inverters and robust reactive-power features to stay “tandem-ready” when flexible products commercialize.

• Ask vendors for third-party data (NREL/Fraunhofer certificates, bending cycles, thermal cycling) before considering flexible tandem on critical roofs.

Bottom line

LONGi’s 33.35% flexible tandem isn’t just another lab stat—it’s a concrete signal that lightweight, high-efficiency PV is getting closer to real projects. Keep your current pipeline moving with bankable modules, but plan for flexibility in BOS and inverter selection so you can adopt next-gen form factors when they’re productized