Recently, a groundbreaking research on low-cost silicon heterojunction (SHJ) cell from Maxwell has been published in Nature Energy, the world's top academic journal focusing on energy research. This paper delves into the methodology and fundamental principles underpinning the creation of SHJ solar cell, boasting an impressive photoelectric conversion efficiency of 25.94%. This achievement is attributed to the integration of a transparent conductive oxide (TCO) thin film process with a low-indium content and copper-plated electrodes.
The paper, which is titled Silicon solar cell with undoped tin oxide transparent electrode, with Suzhou Maxwell Technologies Co., Ltd. as the main unit, and Ms. Cao Yu, the head of solar cell R&D center, as the main author, is a collaborative effort involving Maxwell team, Nankai University and SunDrive Corporation.
The critical cell technologies, including TCO films and deposition processes, were innovated by the Maxwell team. The equipment used in the solar cell preparation process in this paper is all home-made (including the equipment used in texturing and cleaning, chemical vapor deposition, physical vapor deposition and screen printing).. Throughout this progression, the Maxwell team meticulously optimized the sputtering unit within the physical vapor deposition (PVD) equipment to reduce the target material consumption. This optimization was coupled with a novel approach involving a low-indium layered film (with 50% indium to minimize indium consumption substantially. This dual-pronged approach not only slashes cell manufacturing costs but also upholds its distinct high-efficiency attributes.
Nankai University provided technical support for testing and mechanism analysis. Simultaneously, the SunDrive team contributed the electroplated copper electrodes of the champion cell.
About Nature Energy
Nature Energy stands as a prestigious sub-journal under the umbrella of the top internationally renowned publication, Nature. It mainly focuses on significant breakthroughs within the energy sector, spotlighting high-quality research findings that showcase notable advancements. The influence and popularity of Nature Energy rank top 1 in the industry all year round. It holds a coveted place within the authoritative SCI database. Notably, in 2022-2023, it boasted an impressive impact factor of 56.7, while maintaining an annual publication volume of approximately 100 articles.
Elaborate Research Findings
The limited supply of rare indium and the high cost of silver paste are among the most critical problems that the mass production of SHJ solar cells will face. To overcome the obstacle of indium-based transparent electrodes for high-efficiency SHJ solar cells, the R&D Team of Maxwell successfully prepared cheap and mass-producible undoped tin oxide (SnOx) electrode materials by sputtering at room temperature. SnOx films have excellent chemical stability and can withstand corrosion by acid and alkali solutions during electroplating processes. The team also reduced the contact resistance with n-μc-SiOx:H utilizing hydrogenated transition metal-doped indium oxide (IMO:H)+SnOx bilayer films, which facilitates the enhancement of the fill factor (FF) and further improves the performance of the SHJ solar cells.
To curtail the consumption of the precious metal "silver" during cell manufacturing, the team ingeniously employed a copper plating process. This strategic approach entailed elevating the height-to-width ratio of the electrode, consequently augmenting the cell's conversion efficiency. Simultaneously, this innovation eliminated the costly requirement of silver paste.
Ultimately, by fusing low-indium TCO and a copper-plated electrode, the Maxwell team triumphed in achieving an ISFH-certified efficiency of 25.94% (a total area of 274.4cm2). These remarkable research findings harbor the potential to be extended to other tin oxide rotating targets dopped with trace elements. The utilization of the magnetron sputtering system, crafted by Maxwell, unlocks the doors to large-scale production applications. In addition, the company's endeavors extend to the research and development of copper plating complete line equipment, encompassing pivotal components such as PVD seed layer equipment, graphical equipment, and plating equipment.
As an industry-leading solar cell equipment manufacturer, Maxwell channels substantial efforts into technological research and development. Anchored by a seasoned research and development team with over a thousand personnel, combined with augmented research investments year by year, the company perpetuates momentum for innovative technological strides. Within the realm of SHJ technology, Maxwell has carved significant breakthroughs, notably introducing pioneering technology for bifacial microcrystalline SHJ high-efficiency cells, complete with their complete line manufacturing equipment. These strides have catalyzed marked improvements in SHJ cell efficiency. The company's successes further extend to the development of technology for Non-Busbar SHJ cells and its module stringer equipment, resulting in substantial reductions in silver consumption and associated costs. As a testament to our exceptional research and development capabilities and trailblazing achievements, Maxwell clinched recognition as a "National Enterprise Technology Center" at the end of the previous year.
The unveiling of Maxwell's innovative findings presents pragmatic solutions that trim costs and amplify the efficiency for manufacturers of SHJ cells. This achievement is poised to substantially propel the scaled application of SHJ technology, ultimately bolstering the enduring expansion of solar energy.