Surpassing Shockley–Queisser efficiency limit in photovoltaic cells

The 33 % Shockley–Queisser (S-Q) ceiling has stood as the ultimate barrier for single-junction photovoltaics since 1961. Now, Prof. Zhigang Li (Taizhou University) and Prof. Bingqing Wei (University of Delaware) report the first experimental breach: n-type monocrystalline Si cells delivering 50–60 % power-conversion efficiency at 30–50 K, effectively doubling the room-temperature record and opening a practical route to cryogenic and deep-space power.

Why Low-Temperature PV Matters

• Freeze-Out Paradox: Below ~150 K conventional cells collapse as carriers become trapped; prior wisdom declared “cooler ≠ better”.
• Thermal-Loss Suppression: Phonon population plummets, hot-carrier cooling slows and VOC can approach the band-gap energy.
• Space & Quantum Applications: Lunar South-Pole rovers, superconducting electronics and quantum sensors demand watt-level power at 30–40 K where sunlight is weak but constant.

Innovative Design & Features

• Cryogenic Hot-Carrier Management: Laser lines tuned 0.1–0.4 eV above Eg generate mobile photocarriers that outrun lattice cooling, raising VOC to 1.1 V (≈ Eg).
• Impact-Ionization Boost: Momentum-conservation rules relax at <50 K; 980 nm photons (≈ Eg) trigger multiple-exciton generation, pushing EQE >140 %.
• Thickness–Penetration Matching: Micro-thin cells (<3 µm) paired with 635 nm light suppress carrier freeze-out while maintaining near-unity absorptivity.
• Intensity-Independent Gain: PCE plateau is robust from 0.01 to 1 sun, enabling star-light harvesting at 2.7 K cosmic-background temperature.

Applications & Future Outlook

• Lunar Polar Missions: Remote light-emitting reflectors on crater rims can wirelessly power mining bots operating in permanent shadow.
• Deep-Space Probes: Star-light PV with 50 % efficiency extends mission life without nuclear sources.
• Next Steps: Team is fabricating 4 cm² flight-style cells, testing under rapid thermal cycling (20–300 K) and 1 MeV proton irradiation to qualify for NASA Commercial Lunar Payload Services.

This work rewrites the low-temperature PV playbook, turning the once-dreaded freeze-out regime into an ultra-efficiency window—pointing toward >50 % single-junction devices for extreme-environment energy harvesting. Stay tuned for vacuum-chamber and lunar-simulant tests from the Wei–Li joint lab!