Tandem

EneCoat Technologies has announced a conversion efficiency of over 30% with a 4-terminal tandem cell consisting of stacked perovskite and crystalline silicon solar cells in a joint development project with Toyota Motor Corporation. 

This achievement underscores the profound research and development capabilities of both companies in the field of perovskite solar cells and accelerates the practical application of high-efficiency solar cells, which is the objective of the joint development project. In this project, the two companies focused on the transmittance of perovskite solar cells and succeeded in improving the infrared transmittance to 81%.

Researchers from China's Hebei University of Technology, Fudan University, Fuyang Normal University, Chinese Academy of Sciences (CAS), Macau University of Science and Technology, Kunming University of Science and Technology and France's CNRS have reported an innovative passivation strategy that is said to enable record power conversion rates and enhanced operational longevity of single junction and tandem perovskite solar cells (PSCs).

The team has developed this innovative strategy to address the issue of interfacial trap-assisted nonradiative recombination, which has been known to hinder the performance of perovskite-based photovoltaic technologies. The new passivator is identified as L-valine benzyl ester p-toluenesulfonate (VBETS) and using it under optimal conditions yielded PSCs that achieved a power conversion efficiency (PCE) of 26.28%. 

Researchers from EPFL and CSEM recently fabricated efficient (>20 %) and stable (T80 ∼ 720 h) planar FAPbI₃-based perovskite (1.54 eV) solar cells via a hybrid evaporation-spin coating process. 

FAPbI₃-based perovskite films were fabricated via a hybrid two-step evaporation-spin coating method in an inverted (p-i-n) configuration, and the effects of optimized parameters on the film growth and devices’ performances were investigated. Transferring these films into tandem devices atop single-side textured silicon heterojunction bottom cells, the team obtained an efficiency of >24 % under AM1.5 G illumination for monofacial devices with an active area of 1.21 cm². Furthermore, the bifacial devices generated >27 mW cm⁻² power output with 15 % rear illumination fraction.

Monolithic all-perovskite tandem solar cells present a promising approach for exceeding the efficiency limit of single-junction solar cells. However, the substantial open-circuit voltage loss in the wide-bandgap perovskite subcell hinders further improvements in power-conversion efficiency. Now, researchers from China's Nanjing University, Renshine Solar (Suzhou) and Ecole Polytechnique Fédérale de Lausanne (EPFL) have developed wide-bandgap perovskite films with improved crystal orientation that suppress non-radiative recombination. 

The team showed that using two-dimensional perovskite as an intermediate phase on the film surface promotes heterogeneous nucleation along the three-dimensional perovskite facets during crystallization. Preferred orientations can be realized by augmenting the quantity of two-dimensional phases through surface composition engineering, without the need for excessive two-dimensional ligands that otherwise impede carrier transport. 

JinkoSolar has announced that it has achieved a significant breakthrough in the development of its N-type TOPCon-based perovskite tandem solar cell. Independently tested by the Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, the cell achieved an impressive conversion efficiency of 33.84%, surpassing JinkoSolar's previous record of 33.24%. This achievement marks the 27th time JinkoSolar has set a world record for efficiency and power output for PV products.

The record-breaking perovskite tandem solar cell utilizes JinkoSolar's N-type high-efficiency monocrystalline TOPCon solar cell as the bottom cell, enhanced by significant advancements across multiple key technologies. Innovations such as full-area passivated contact technology, perovskite interfacial defect passivation technology, and bulk defect passivation technology have contributed to the enhanced efficiency of the perovskite/TOPCon tandem cell. This achievement highlights the compatibility of TOPCon as a mainstream solar cell technology with the next-generation perovskite/silicon tandem cell technology, paving the way for new possibilities in the future development of the photovoltaic industry.

Hanwha Solutions Qcells Division (Hanwha Qcells), a global leader in complete clean energy solutions, has announced a new world record, reaching 28.6% for tandem solar cell efficiency on a full-area M10-sized cell that can be scaled for mass manufacturing. This result was achieved despite having only begun large-area tandem development in 2023.

“The tandem cell technology developed at Hanwha Qcells will accelerate the commercialization process of this technology and, ultimately, deliver a great leap forward in photovoltaic performance,” said Danielle Merfeld, Global CTO at Hanwha Qcells. “We are committed to advancing the next generation of solar energy efficiency and will keep investing significantly in research and development to drive progress in this field, as every kilowatt counts on the path to building a more sustainable future.”  

In November 29, Hangzhou Xianna Optoelectronic Technology Co., Ltd. delivered its perovskite α-tandem modules for the China Three Gorges New Energy 50 MW PV demonstration project, in what is said to mark the first commercial application of four-terminal perovskite-silicon tandem modules in China. 

Once the PV power plant utilizing these tandem modules is completed and connected to the local grid, it will significantly alleviate the local grid's supply-demand imbalance, reduce environmental pollution, and improve air quality. The design work for a 500 kW demonstration plant has already been completed, with plans to collaborate with engineering institutes for on-site module layout design. The demonstration plant is expected to be connected to the grid and operational by the end of 2024.

According to reports, China Huaneng (China Huaneng Group Co., Ltd.) has achieved a power conversion efficiency of 26.12% on its self-developed large-size perovskite silicon tandem cell, and the result was certified by a third-party testing institution.

China Huaneng stated that after more than ten years of research, it has established a systematic platform for R&D, pilot testing and analysis of perovskite cells, mastered the technology of large-area high-efficiency perovskite and tandem solar modules, and taken the lead in the application of perovskite photovoltaic technology, carried out the verification of kilowatt-scale solar systems using perovskite modules in various scenarios, and built the first megawatt-scale solar system using large-scale perovskite products in overseas.

Researchers from Huaqiao University, Gold Stone (Fujian) Energy Company, Beijing Huairou Laboratory and Kunshan Shengcheng Photoelectric Technology have reported a four-terminal (4T) perovskite-silicon solar cell with a perovskite-based top cell, with an energy bandgap of 1.67 and lower surface defects. 

Structure of the 4T perovskite/silicon tandem solar cells. Image from Nature Communications

The team integrated a wide-bandgap perovskite solar cell with a hybrid back contact device in a four-terminal tandem cell that achieves high efficiency and stability. The group used a new surface passivation strategy that reportedly helped gain the cell's strong performance.

Over the past five years, six Fraunhofer Institutes combined their expertise in the Fraunhofer lighthouse project "MaNiTU" to identify the most sustainable paths to market of perovskite-silicon tandem solar cells made of stable materials and manufactured using scalable production processes. They were able to show that high cell efficiencies can be achieved using industry-oriented processes, however, they found that such high efficiencies were only currently achievable with lead perovskite materials. Based on these findings, the researchers developed suitable recycling concepts to ensure sustainability.

In the "MaNiTU" project, the Fraunhofer researchers produced new materials with perovskite crystal structures and compared them with existing materials at the cell level. The comparisons showed that high efficiencies can only be achieved with lead perovskites. They then successfully fabricated highly efficient demonstrators, for example, a perovskite silicon tandem solar cell of more than 100 square centimeters with screen-printed metallization and produced mini modules for single and interconnected tandem solar cells. Subsequent life cycle analyses showed that by using suitable production and recycling processes and degradation rates comparable to today's silicon technology, it is feasible to make a sustainable product.