LONGi's Double-end Tandem Perovskite Solar Cells Have An Efficiency Of 34.85%

In April 2025, LONGi announced that its independently developed crystalline silicon-perovskite double-end tandem solar cells were certified by the National Renewable Energy Laboratory (NREL) of the United States, with a power conversion efficiency of 34.85%, once again breaking the global record of this technology route. This breakthrough not only marks the entry of photovoltaic technology into a new era of "34%+", but also means that crystalline silicon-perovskite stacked cells have officially broken through the theoretical efficiency limit of single-junction cells (33.7%), laying the foundation for the next generation of ultra-high-efficiency photovoltaic technology.

LONGi's technical path is based on crystalline silicon cells, and achieves spectral complementarity through the stacking design of perovskite layers. Specifically, the perovskite layer (bandgap of about 1.7 eV) is responsible for absorbing the visible light part, while the crystalline silicon layer (bandgap of 1.1 eV) captures infrared light. The two work together to increase the solar energy conversion efficiency to 34.85%. The core of this structure lies in the breakthrough of interface engineering. The LONGi team has developed a double-layer interlaced passivation strategy. Through the synergistic effect of lithium fluoride (LiF) and ethylenediamine diiodide (EDAI) molecules, it effectively suppresses non-radiative recombination at the interface and optimizes the carrier transfer efficiency.

It is worth noting that LONGi's technology iteration speed far exceeds industry expectations: the efficiency exceeded 33.9% in November 2023, increased to 34.6% in June 2024, and reached a new high in April 2025. This "fast iteration" capability stems from its R&D system of "mass production generation, R&D generation, and reserve generation", as well as in-depth cooperation with institutions such as Soochow University, Huaneng Clean Energy Research Institute, and Hong Kong Polytechnic University. For example, the research of Professor Li Yaowen's team at Soochow University on perovskite lattice stress regulation provides key support for improving battery stability; Huaneng Clean Energy Research Institute has contributed engineering experience in large-area component preparation and industrial application.

Breakthrough In Efficiency Ceiling

The theoretical limit efficiency of crystalline silicon-perovskite tandem cells is as high as 43%, far exceeding the 29.4% of single crystalline silicon cells. LONGi's 34.85% efficiency is close to 80% of this theoretical value, leaving ample room for subsequent technology upgrades. If the triple-junction tandem (such as perovskite/crystalline silicon/perovskite) technology matures in the future, the efficiency is expected to be further increased to more than 40%, completely rewriting the efficiency competition landscape of the photovoltaic industry.

Disruptive Optimization Of Cost Structure

The silicon material cost of traditional crystalline silicon cells accounts for about 40%, while the tandem cells can reduce the silicon material cost to less than 20% by reducing the thickness of silicon wafers (from 180 μm to less than 100 μm) and increasing the power generation per unit area. In addition, the solution preparation process of the perovskite layer (such as slit coating and inkjet printing) consumes only 1/10 of the energy of crystalline silicon cells, further reducing manufacturing costs. It is estimated that the levelized cost of electricity (LCOE) of stacked cells can be reduced by 25% compared with traditional PERC cells, and it has significant competitiveness in distributed photovoltaics, BIPV and other scenarios.

Release Of Industrial Chain Synergy Effect

Longi's technological breakthroughs will accelerate the maturity of the perovskite industry chain. For example, TCO glass (transparent conductive oxide), as a key material for the perovskite layer, has increased its localization rate from 30% in 2023 to 70% in 2025; the large-area laser scribing technology developed by Huaneng Clean Energy Research Institute has increased the yield of perovskite modules from 85% to 95%. In addition, Longi's cooperation with GCL-Poly Optoelectronics, Xianna Optoelectronics and other companies is building a "perovskite-crystalline silicon" collaborative industrial ecology.

Although The Efficiency Breakthrough Is Exciting, Commercialization Still Faces Multiple Challenges:

Stability and life bottleneck

Perovskite materials are sensitive to water, oxygen, light and temperature, and lack long-term stability. Longi's stacked cells have not yet disclosed specific life data, but the industry generally believes that its T80 life (the time it takes for efficiency to decay to 80%) needs to exceed 5,000 hours to meet commercial requirements. To solve this problem, Longi may have adopted the following technical paths:

Interface passivation: For example, the dual host-guest complexation strategy developed by Zhang Hong's team at Fudan University can extend the life of perovskite cells to 1,050 hours.

Packaging technology: The graphene-polymer enhancement technology of Huaneng Clean Energy Research Institute can increase the life of perovskite modules to 3,670 hours.

Complexity of mass production process

Dual-terminal tandem cells require precise control of the lattice matching and interface contact between the perovskite layer and the crystalline silicon layer. The following problems need to be solved during mass production:

Thin film uniformity: The thickness of the perovskite layer needs to be controlled at 300-500 nm, and the thickness deviation needs to be less than 5%.

Process compatibility: There is a contradiction between the high-temperature process of crystalline silicon cells (>800℃) and the low-temperature preparation of perovskites (<150℃), and new materials such as low-temperature silver paste need to be developed.

Policy and market uncertainty

Although the country's "14th Five-Year Plan" lists perovskites as key technologies, there is currently a lack of clear subsidy policies and industry standards. In addition, the recycling system for perovskite components has not yet been established, and lead pollution issues may cause environmental disputes.

Longi's 34.85% efficiency breakthrough marks the leap of photovoltaic technology from "crystalline silicon dominance" to "stacked era". This breakthrough is not only a technological victory, but also a model of collaborative innovation in the industrial chain - Suzhou University's material research, Huaneng's engineering capabilities, and Hong Kong Polytechnic's device design together constitute the cornerstone of technological breakthroughs.

Looking ahead, crystalline silicon-perovskite tandem cells will reshape the industry landscape in the following areas:

Distributed photovoltaics: Its lightweight (module weight <5 kg/㎡) and high power density (>400 W/㎡) characteristics will promote the outbreak of BIPV, vehicle-mounted photovoltaics and other scenarios.

Centralized power stations: Efficiency improvement can reduce land occupation per unit area, which is more advantageous in areas with scarce land resources.

Space exploration: The research and development of flexible tandem cells may provide more efficient energy solutions for deep space probes.

However, the road to commercialization still needs to break through multiple obstacles such as stability, mass production process and policy support. LONGi's technological breakthrough has pointed the way for the industry, but to achieve the "perovskite revolution", the joint efforts of the entire industry chain are still needed. In the next five years, the photovoltaic industry will usher in the dual transformation of technological iteration and industrial reconstruction, and LONGi's 34.85% efficiency is the starting point of this transformation.