Stability

Scientists from King Abdullah University of Science and Technology (KAUST) and Solar Energy Research Institute of Singapore (SERIS) have examined the potential-induced degradation (PID) susceptibility of perovskite-silicon tandem devices fabricated in their lab. They exposed tandem cell devices to PID stress and found that they lost as much as 50% of their initial performance after just one day. This led the team to assess that more work needs to be done on the issue before perovskites can be commercialized and deployed at scale.

Research on perovskite solar cells' stability challenges has largely focused on the material’s sensitivity to moisture, high temperatures, and other environmental conditions. Potential-induced degradation (PID), caused by currents leaking from the cell and driving various damaging mechanisms, has long been a threat to performance in silicon PV modules, but has so far been much less explored in emerging PV technologies such as perovskite.

Scientists from Kaunas University of Technology and Vilnius University in Lithuania and University of Colorado in the U.S have proposed a method for increasing the stability and performance of perovskite solar cells. The team synthesized a new class of carbazole-based cross-linkable materials, which are resistant to various environmental effects, including strong solvents used in the production of solar cells.

When applied as hole transporting layers, the new materials helped achieve the 16.9% efficiency of the inverted-architecture perovskite cells at the first attempt. It is expected to reach higher efficiency upon optimization.

Researchers at the U.S. Department of Energy’s (DOE’s) National Renewable Energy Laboratory (NREL), in collaboration with scientists from the University of Toledo, the University of Colorado–Boulder, and the University of California–San Diego, have announced a technological breakthrough and constructed a perovskite solar cell with the dual benefits of being both highly efficient and highly stable.

A unique architectural structure enabled the researchers to record a certified stabilized efficiency of 24% under 1-sun illumination, making it the highest reported of its kind. The highly efficient cell also retained 87% of its original efficiency after 2,400 hours of operation at 55 degrees Celsius.

Scientists from China's Huaqiao University and Henan Normal University have developed a controllable moisture treatment for perovskite films that can promote the mass transportation of organic salts. The films were used to fabricate a 0.2 cm² perovskite solar cell that was able to retain 80% of its initial efficiency after 1200 h.

The group investigated the effects of moisture in the air on the intermediate and final perovskite films in solar cells and developed the controllable moisture treatment that relies on a series of nitrogen (N₂)-protected characterization techniques.

Sweden-based Evolar, which has developed a unique perovskite-based solar cell technology, has announced that it can now present results from climate tests that show at least 25 years lifespan with stable electricity yield.

Evolar's tandem technology reportedly provides 25% more electricity at a low cost. However, to be commercially ready, solar panels also need to have a guaranteed lifespan of at least 25 years with stable electricity generation throughout this period.

Perovskite LEDs can be produced quite easily and at low cost. They show great promise as they are lightweight and can offer flexibility compared to OLEDs, with color purity and tunability similar to LEDs based on III-V semiconductors. However, the poor device stability of perovskite LEDs will have to be overcome before commercial applications can emerge. Typical lifespans of perovskite LEDs are on the order of 10 to 100 hours. In contrast, the minimum lifetime required for an OLED display is 10,000 hours. It is currently challenging to reach this threshold, as halide perovskite semiconductors can be intrinsically unstable due to the ionic nature of their crystal structures—the ions can move around when voltages are applied to the LEDs, leading to material degradation.

In their recent work, a research group led by Prof. Di Dawei and Prof. Zhao Baodan at the College of Optical Science and Engineering of Zhejiang University discovered that by using a dipolar molecular stabilizer, it is possible to make efficient and stable perovskite LEDs with ultralong lifetimes, satisfying the demands of commercial applications. The research was carried out in collaboration with the research groups of Prof. Li Cheng at Xiamen University, Prof. Hong Zijian at Zhejiang University, and Prof. Li Weiwei at NUAA and formerly at Cambridge University. 

Researchers from Ulsan National Institute of Science and Technology (UNIST), Wuhan University of Technology and Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory have announced their success in manufacturing a high-efficiency, stable perovskite solar cell through a vacuum thin film deposition process.

Vacuum thin film deposition is a technique that is already widely used in the manufacture of large OLED TVs by evaporating raw materials in a vacuum and coating them thinly on a substrate. The perovskite solar cell developed this way displayed a photovoltaic-to-electricity conversion efficiency of 21.4%, which the team said is the highest among perovskite solar cells manufactured by vacuum thin film deposition process.

University of New South Wales (UNSW) team, led by renowned PV scientist Martin Green, have shown that perovskite solar cells may be especially susceptible to damage from reverse bias, caused by uneven shading or other issues that may appear in real-world environments. Both the reverse-bias itself and resulting build up of heat can cause several of the materials commonly used in perovskite solar cells to degrade, and these issues have received only limited attention in research published thus far. 

Stability issues with perovskite solar cells linger, despite impressive research achievements in the last few years. Much of the research focused on improving stability to date has focused on the issues that arise under normal operating conditions – for example sensitivity to oxygen and moisture, which can be solved through encapsulation, or degradation under UV light, which can be solved with reflective coatings. Other issues, however, may present serious challenges to developing perovskite devices that can function in outdoor conditions for years and even decades. “…thermal degradation and reverse-bias instability are remaining issues that pose challenges even for intrinsically much more stable silicon cells, suggesting that innovative approaches may be required to satisfactorily address these for perovskite cells”, explain the authors of the new paper.

Researchers led by Prof. LIU Shengzhong from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) have developed a facile surface redox engineering (SRE) strategy for vacuum-deposited NiOx to match the slot-die-coated perovskite, and fabricated high-performance large-area perovskite submodules.

Inverted PSCs could be even more valuable than their normal counterparts because the former have easily-mitigated hysteresis behavior and long-term durability. NiOx has been demonstrated as a promising hole transport material for inverted PSCs. But for most vacuum-processed NiOx films, the relatively hydrophobic surface attenuates the adhesion of perovskite ink, making it challenging to deposit large-area perovskite films.

The U.S. Department of Energy Solar Energy Technologies Office (SETO) selected University of Arizona chemical and environmental engineering associate professor Erin Ratcliff for a $300,000 grant to advance the near-term scalability of perovskites.

“Perovskites are the highest-performing printable solar cell technology,” Ratcliff said. “But the operating hypothesis in the field is that defects are contributing to instability”. With the SETO grant, Ratcliff and her team will develop a method for detecting these defects during manufacturing. The low-cost, scalable method will help scientists understand the way different parts and materials of the manufacturing process may contribute to defects and instability, and, in turn, how to mitigate these effects. The grant is part of SETO’s Small Innovative Projects in Solar 2022 Funding Program, which funds targeted, early-stage ideas in solar energy research that can produce significant results within the first year of performance. Nineteen projects received a total of $5 million in funding.