Perovskite solar cells (PSCs) are an innovative photovoltaic technology with efficiencies close to current traditional Silicon. However, perovskite-based devices have low stability in environmental conditions, particularly in high relative humidity (RH%) environments. The moisture cause the degradation of the perovskite and a several power conversion efficiency (PCE) losses. Our invention addresses the stability issue by introducing the highly hydrophobic material ZIF-8 into the device, which acts as a moisture barrier preventing perovskite degradation and increasing device lifespan.
Patent Status
Pending
Priority Number
102021000031412 PCT/IB2022/062299
Priority Date
15/12/2021
License
International
Market
The instability problem of perovskite solar cells is the main issue to be solved before commercialization.
Currently, there are numerous efforts and investments in both academic and industrial fields aimed at solving this problem. The perovskite solar cell market is predicted to reach a size of 5-10 billion USD by 2030 (alliedmarketresearch.com). Our invention initially targets a niche in this market, with a focus on the academic sector, and then expands on a large scale to the industrial market.
Problem
Perovskite solar cells are photovoltaic devices that aim to be the new frontier in the field of renewable energies. The efficiencies achieved (25.7%) are very close to current Silicon panels, however, their easy processability, excellent optoelectronic properties, and industrial scalability make them the most suitable technology to replace current ones. Perovskites have a crystal structure of the ABX3 type, where A is the organic cation (methylammonium, formamidinium, etc.), B is the metal cation (Pb2+), and X is the halogen. High humidity conditions promote the formation of the hydrated complex with the perovskite causing structural deformation. This results in a decay of the optoelectronic properties and ultimately the efficiency of the devices. To overcome this problem, there are various encapsulation techniques based on processes in which the device is isolated from the external environment through the use of hydrophobic polymers. However, not all devices have shown a sufficient increase in stability to make them commercially available, and the available polymers have shown issues, such as EVA, related to partial degradation following exposure to high humidity conditions.
Current technology limits / Solutions
Currently, various strategies are being adopted to increase the stability of perovskite-based devices. The use of interlayers and passivating layers between the perovskite film and the other layers that form the cell has led to an increase in device stability, but they are still not comparable to the working lifetime of a silicon panel. Better results have been achieved with the use of encapsulating polymers that are used in the glass-glass lamination process. The perovskite cell is isolated from the external environment by encapsulation between two glass sheets; butyl rubber is used as a sealant while the most commonly used encapsulating polymers are Surlyn, PDMS, EVA, but also POE (polyolefin) and TPU (thermoplastic polyurethane). The key parameters for evaluating an encapsulant are transmittance in the absorption range of the photoabsorbing material, Tg (glass transition temperature), delamination resistance, chemical stability, WVTR (water vapor transmission rate), and OTR (oxygen transmission rate). Butyl rubber is the most commonly used sealant because it has excellent WVTR and OTR values, and it also has excellent adhesive properties. On the other hand, encapsulating polymers have higher WVTR and OTR values, which means a greater ability of the oxygen and moisture to penetrate into the device.
Killer Application
Through the use of our technology, the introduction of a highly hydrophobic material such as ZIF-8 into the encapsulant allows to increase the contact angle and makes it more hydrophobic towards moisture. The application of ZIF-8 therefore allows to maintain PCE and other photovoltaic parameters constant over time, preventing the degradation mechanism of the perovskite.
– Improvement of performance in stability of perovskite-based solar cells in academic and research and development environments
– Improvement of performance in stability of perovskite-based solar panels in industrial applications
Our Technology and Solutions
The device integrating ZIF-8 makes the surface of the encapsulating material hydrophobic. ZIF-8 is a porous material belonging to the family of MOFs (metal-organic frameworks) in which a zinc atom is coordinated by methyl-imidazole. The organic component makes the material highly hydrophobic, which can then be deposited on the polymer, increasing its contact angle and preventing both water and moisture permeation into the devices. The PCE of devices with ZIF-8 have more stable photovoltaic performance over time compared to devices with classical encapsulants.
Advantages
The use of a highly hydrophobic material such as ZIF-8 integrated with the use of encapsulating polymers allows for increased stability of perovskite solar cells over time while maintaining constant photovoltaic parameters and efficiency. The application of ZIF-8 also allows for better performance of polymers with lower values of WVTR and OTR, making them potential candidates for encapsulating the final device. Furthermore, ZIF-8 can be easily and reproducibly synthesized via solvothermal methods and its integration into the device can be carried out using simple deposition methods.
Roadmap
In the future, prototypes of devices with different layout will be developed: ZIF-8 inside the encapsulating material and on the outer surface of the sealant material. Subsequently, the devices will be tested through standardized tests in high humidity conditions, and the WVTR and OTR values of the encapsulating polymers integrating ZIF-8 will be measured.
TRL
Team
