Very effective perovskite solar cells with enhanced security as well as reduced lead leakage

• While the power conversion efficiency of perovskite solar cells (PVSCs) - a future of solar cells - has currently greatly enhanced in the past decade, the problems of instability and also potential ecological influence are yet to be gotten rid of. Lately, scientists from City University of Hong Kong (CityU) have developed a novel technique which can concurrently tackle the leakage of lead from PVSCs as well as the stability problem without compromising efficiency, paving the way for real-life application of perovskite photovoltaic or pv technology.

The study team is co-led by Professor Alex Jen Kwan-yue, CityU's Provost and Chair Professor of Chemistry and also Materials Science, along with Professor Xu Zhengtao as well as Dr Zhu Zonglong from the Department of Chemistry. Their research findings were recently released in the scientific journal Nature Nanotechnology, titled "2D metal-organic framework for secure perovskite solar cells with reduced lead leak".

Currently, the highest power conversion efficiency of PVSCs has been on par with the advanced silicon-based solar cells. Nevertheless, the perovskites made use of have lead part which raises a concern for possible environmental contamination. "As the solar cell ages, the lead species can leak with the devices, e.g. via rainwater right into the dirt, posturing a poisoning threat to the setting," clarified Professor Jen that is a professional in PVSCs. "To place PVSCs into large-scale business uses, it needs not just high power conversion efficiency but additionally lasting device security and minimised ecological influence."

Collaborating with Professor Xu whose expertise is products synthesis, Professor Jen and Dr Zhu led the team to get rid of the above difficulties by using two-dimensional (2D) metal-organic frameworks (MOFs) to PVSCs. "We are the first team to make PVSC devices with reduced lead leak, excellent lasting security and also high power conversion effectiveness concurrently," Professor Jen summarised their research advancement.

Multi-functional MOF layer

Metal-organic structure (MOF) products have actually been formerly applied as scaffolds to theme the growth of perovskites. Researchers have actually likewise used them as ingredients or surface modifiers to passivate (to reduce the reactivity of the product's surface) the flaws of perovskites for boosting the gadget efficiency and also security.

Nevertheless, the majority of the 3D MOFs are fairly electrical shielding with reduced charge-carrier flexibility, thus improper to be made use of as the charge-transporting materials.

However the MOFs prepared by Professor Xu is various. They are honeycomb-like, 2D framework geared up with countless thiol groups as an essential functionality. They possess appropriate energy levels, enabling them to be an electron-extraction layer (also called "electron-collection layer") where electrons are lastly gathered by the electrode of the PVSCs. "Our molecular engineered MOFs have the home of a multi-functional semiconductor, as well as can be made use of to boost the charge extraction efficiency," described Professor Xu.

Trapping the lead ions to prevent contamination

A lot more importantly, the dense varieties of thiol and also disulphide teams in the MOFs can "record" heavy metal ions at the perovskite-electrode user interface to alleviate lead leak.

" Our experiments showed that the MOF used as the external layer of the PVSC tool caught over 80% of the dripped lead ions from the abject perovskite and also formed water-insoluble facilities which would not contaminate the soil," Professor Jen explained. Unlike the physical encapsulation techniques made use of in decreasing lead leak in other research studies, this in-situ chemical sorption of lead by the incorporated MOF component in the device was located to be more effective and also lasting for long-term practical applications.

Lasting functional stability achieved

Additionally, this MOF product might shield perovskites against wetness as well as oxygen while maintaining high effectiveness.

The power conversion efficiency of their PVSC device changed with MOF might get to 22.02% with a fill element of 81.28% and open-circuit voltage of 1.20 V. Both the conversion performance and the open-circuit voltage taped are among the highest possible worths reported for the planar inverted PVSCs. At the same time, the gadget displayed remarkable security in an ambient environment with the relative moisture of 75%, keeping 90% of its first efficiency after 1,100 hours. On the other hand, the power conversion performance of the PVSC without MOF dropped substantially to less than 50% of its initial value.

Also, their gadget kept 92% of its initial efficiency under constant light irradiation for 1,000 hours at 85 C. "Such degree of security has currently satisfied the requirement for commercialisation set by the International Electrotechnical Commission (IEC)," claimed Dr Zhu.

" This is an extremely substantial result which confirmed our MOF technique is practically viable and has the possibility in commercialising the PVSC technology," added Professor Jen.

Extremely reliable PVSCs for tidy energy applications

It took the group nearly 2 years to achieve this encouraging study. Their next action will be to further boost the power conversion efficiency as well as check out the methods to decrease the production cost.

"We really hope in the future the production of this sort of PVSCs would resemble 'publishing out' newspapers and also quickly scaled up in production, assisting in the large-scale deployment of highly reliable PVSCs for clean power applications," concluded Professor Jen.