China firm sets world record with 34.85% efficient crystalline silicon PV tandem solar cell
A Chinese solar technology company has achieved a significant breakthrough in solar cell R&D. A two-terminal crystalline silicon-perovskite tandem solar cell, developed by Longi, achieved a conversion efficiency of 34.85%. The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) confirmed the efficiency.
As a leading technology pathway for next-generation ultra-efficient solar cells, crystalline silicon-perovskite tandem solar cells boast a theoretical efficiency limit of 43%, far surpassing the Shockley-Queisser (SQ) limit for single-junction solar cells (33.7%). The Chinese firm’s tandem solar cell R&D team has consistently pushed the boundaries of this technology with power conversion efficiency records.
LONGi refreshed its own world records
With the recent breakthrough, LONGi has refreshed its own world records in both single-junction crystalline silicon solar cells and crystalline silicon-perovskite tandem solar cells.
The company claims that the dual achievement reinforces LONGi’s position as the “Dual-Champion” in solar innovation and solidifies its leadership in core photovoltaic technologies.
Back in November 2023, Longi achieved a tandem solar cell efficiency of 33.9%, approaching the SQ limit. While in June 2024, the company broke its own record with 34.6% conversion efficiency.
Now, within a year, LONGi has achieved a new world record of 34.85% efficiency.
Based on a bilayer interface passivation strategy
In September, Longi’s research team explained that the cell was based on a bilayer interface passivation strategy that reportedly maximizes both electron transport and hole blocking. This is achieved through the incorporation of a thin lithium fluoride (LiF) layer and the deposition of short-chain ethylenediammonium diiodide (EDAI) molecules.
The Longi team had highlighted earlier that the thicker LiF layer may help improve the passivation, but come with a considerable undesirable resistive loss. While the team stressed that the EDAI molecule can chemically passivate the unpassivated areas that are not contacted by the LiF layer, forming nanoscale localized contacts at perovskite/C60 interface, which can provide an optimal tradeoff between passivation and charge extraction.
The company has also maintained that it significantly reduced the crystal-pulling cost through the use of new processes such as large charge, high pulling speed and multi-time crystal pulling, supporting equipment improvement technology, as well as, the introduction of new materials and automatic control system.
With the help of automation in manufacturing, the company claims that it can improve the effective production capacity, greatly reducing the number of workers and improving the consistency of the crystal growth process. Smart automation tools are used to control the single crystal furnace, reducing human intervention in the crystal growth process.
Last week at LONGi’s Wuhu Base in Anhui, the company also announced a groundbreaking achievement: LONGi independently developed Hybrid Interdigitated-Back-Contact (HIBC) crystalline silicon solar cell has attained a 27.81% conversion efficiency, certified by Germany’s Institute for Solar Energy Research Hamelin (ISFH). This milestone elevates the exploration of monocrystalline silicon solar cell efficiency to unprecedented levels, according to a press release.