Key Takeaways & Executive Findings
- •• A record power conversion efficiency of 50%–60% was achieved in Si solar cells by inhibiting the lattice atoms’ thermal oscillations at low temperatures. • Enhancing the light penetration depth can effectively mitigate carrier freeze-out and expand the operational temperature range of silicon cells to 10 K. • The breakthrough challenges the classical Shockley–Queisser limit and opens new avenues for high-efficiency photovoltaics in extreme environments. • The findings have significant implications for powering cryogenic devices and deep-space exploration missions.
Abstract
The Shockley–Queisser (S-Q) model sets a theoretical limit on the power conversion efficiency (PCE) of single-junction solar cells at around 33%. Recently, a PCE of 50%-60% was achieved for the first time in n-type single-junction Si solar cells by inhibiting light conversion to heat at low temperatures. Understanding these new observations opens tremendous opportunities for designing solar cells with even higher PCE to provide efficient and powerful energy sources for cryogenic devices and outer and deep space explorations.
1. Introduction
The Shockley–Queisser (S-Q) model is widely recognized in the scientific community, setting a theoretical limit on the power conversion efficiency (PCE) of single-junction solar cells at around 33% [1]. This limitation arises because most solar energy is lost as heat, especially from photons with energies significantly higher than the solar cell’s bandgap. Breaking the S-Q limit to achieve a considerably higher PCE is highly desirable and a long-standing pursuit for both fundamental and applied research.
To overcome this efficiency barrier, two primary strategies have been proposed [1]. The first involves extracting hot carriers before they lose energy and settle at the band edge, potentially enabling the generation of an open-circuit voltage (VOC) higher than the bandgap (Eg). The second strategy focuses on increasing photocurrent by generating multiple electron–hole pairs through impact ionization, which could lead to an external quantum efficiency (EQE) greater than 100%. Despite these promising approaches, surpassing the S-Q efficiency limits in solar cells remains a formidable challenge.
Reducing the temperature to inhibit thermal loss is a straightforward method; extensive research has examined the impact of temperature on the PCE of solar cells [1]. However, when the temperature is < 150–200 K, the PCE will decrease with decreasing temperature due to the effects linked to carriers. The hypothesis that increasing PCE by cooling no longer applies at low temperatures appears to challenge the law of thermodynamics. Furthermore, the temperature limitation constrains their utility for cryogenic apparatuses and exploratory missions in outer, deep, or planetary environments, such as the lunar South Pole, where the temperature hovers around 30–50 K [2].
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Zhigang Li, Bingqing Wei (2025). Surpassing Shockley–Queisser Efficiency Limit in Photovoltaic Cells. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01844-8
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Frequently Asked Questions
What is the Shockley-Queisser limit?
The Shockley-Queisser limit is a theoretical maximum efficiency of about 33% for a single-junction solar cell, set by the balance of photon absorption and thermalization losses.
How was the efficiency limit surpassed?
By operating silicon solar cells at extremely low temperatures (30-50 K), researchers inhibited thermal oscillations of lattice atoms, reducing energy loss and achieving efficiencies of 50-60%.
What are the practical applications of this breakthrough?
The high-efficiency low-temperature solar cells could power cryogenic devices and spacecraft in deep space or lunar missions where temperatures are very low.
What is carrier freeze-out?
Carrier freeze-out is a phenomenon at low temperatures where dopant atoms do not ionize fully, reducing free carrier concentration. The study suggests enhancing light penetration depth can mitigate this effect.
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