New pathway to improve polycrystalline thin-film solar cell performance

Jun 10, 2021 11:29 AM ET
  • Puzzling out and also checking new ways to enhance the performance of cadmium telluride (CdTe) polycrystalline thin-film photovoltaic products is a common day in the life of National Renewable Energy Laboratory (NREL) research study researchers Matthew Reese and also Craig Perkins.
New pathway to improve polycrystalline thin-film solar cell performance
Image: Unsplash/CC0 Public Domain

Like any type of great puzzlers, they bring interest as well as eager observation to the task. These abilities led them, in time, to make an appealing observation. In fact, their discovery may prove to be an advantage for the next generation of a number of various sorts of thin-film solar cells.

When pieces of solar cell material are taken shape with each other, or "expanded"-- think about a piece of rock candy expanding in layers in a mug of sugar-- they produce a polycrystalline solar cell. With numerous layers come several surface areas, where one layer ends and an additional starts. These surface areas can create issues that restrict the liberty of electrons to relocate, reducing the cell's performance. As the cells are expanded, researchers can introduce particular substances that decrease the loss of electrons at these defects, in a process called "passivation.".

Reese, Perkins, and Colorado School of Mines doctoral trainee Deborah McGott observed that the three-dimensional (3D) CdTe solar cells' surfaces seemed covered in a very thin, two-dimensional (2D) layer that naturally eliminated surface area problems. This 2D passivation layer kinds in sheets on the 3D light-absorbing layer as the cell is expanding, in a common handling strategy that is used around the globe. Despite the ubiquity of this 2D passivation layer, it had not been observed or reported in the research literature. Reese, Perkins, and McGott thought 2D passivation was likewise happening naturally in various other thin-film solar cells, like copper indium gallium selenide (CIGS) as well as perovskite solar cells (PSCs). They understood that this monitoring could bring about the growth of new methods to improve the performance of several sorts of polycrystalline thin-film cells.

To confirm their hypothesis, they discussed it with NREL colleagues in the CdTe, CIGS, as well as PSC research groups. With lots of informal conversations including coffee, corridor chats, and also unscripted conferences, Reese, Perkins, and also McGott came to an "aha" minute. Their CdTe and also CIGS associates confirmed that, while their research study communities were not typically attempting to do 2D surface passivation in the 3D light-absorbing layer, it was, as a matter of fact, happening. The PSC researchers said that they had discovered a 3D/2D passivation effect and were beginning to intentionally include substances in gadget processing to boost performance. The "aha" minute took on much more significance.

" One of the special things about NREL is that we have huge groups of specialists with different pools of understanding working on CdTe, CIGS, as well as PSC technologies," Reese stated. "And we talk with each other! Verifying our hypothesis regarding normally taking place 3D/2D passivation with our coworkers was simple since we share the successes and troubles of our diverse study in an ongoing, informal, and collective way. We pick up from each other. It is not something that typically occurs in scholastic or for-profit-based polycrystalline thin-film solar cell research study, where details is carefully held, and also researchers often tend to stay siloed in their particular modern technology.".

The details of Reese, Perkins, and McGott's discovery are presented in the post "3D/2D passivation as a secret to success for polycrystalline thin-film solar cells," published in the journal Joule.

Sustaining Evidence in the Literature.

To verify their searchings for, McGott conducted a considerable literature search as well as found substantial supporting evidence. The literary works confirmed the existence of passivating 2D compounds in each of the CdTe, CIGS, as well as PSC technologies. No reference was made, however, of the 2D substances' capability to enhance device performance in CdTe and CIGS technologies. While many short articles on PSC innovations noted the normally happening 3D/2D passivation effect and discussed initiatives to intentionally consist of certain compounds in gadget processing, none suggested that this result could be active in various other polycrystalline thin-film photovoltaic technologies.

Polycrystalline thin-film solar cells are made by depositing thin layers, or a thin film, of photovoltaic product on a support of glass, plastic, or steel. Thin-film solar cells are economical, and many people are familiar with their even more one-of-a-kind applications. They can be installed on rounded surfaces-- to power consumer goods, for instance-- or laminated flooring on window glass to create electrical energy while allowing light through. The biggest market for thin-film solar cell applications, however, is for CdTe thin film on stiff glass to make solar modules. CdTe modules are deployed at utility range, where they compete directly with standard silicon solar modules. Currently, industrial thin-film modules are normally less efficient than the best solitary crystal silicon solar modules, making performance improvements a high top priority for polycrystalline thin-film scientists.

Secret Quality of 2D Products.

Reese, Perkins, and McGott's team made use of surface science methods integrated with crystal growth experiments to reveal that the 2D layers existed at and also passivated 3D absorber surface areas in the three leading polycrystalline thin-film photovoltaic innovations. They then assessed the crucial residential or commercial properties of successful 2D materials as well as established a collection of principles for selecting passivating compounds.

Ultimately, the team detailed essential layout approaches that will certainly enable 3D/2D passivation to be utilized in polycrystalline thin-film solar technologies a lot more normally. This is especially essential due to the fact that each 3D material requires a details passivation strategy.

The literature results, incorporated with lab-based monitorings, reveal that 3D/2D passivation may be the key to success in making it possible for next-generation thin-film solar cells, specifically if scientists freely share the expertise established for every innovation. The lack of 3D/2D passivation may also clarify the stalled efficiency improvements of some polycrystalline modern technologies such gallium arsenide. By drawing parallels between the three innovations, Reese, Perkins, and also McGott want to show just how the expertise established in each can-- as well as need to-- be leveraged by various other modern technologies, a strategy that is hardly ever seen in polycrystalline thin-film solar cell research.

Solar Installers, Manufacturers