Researchers from the City University of Hong Kong have invented a multifunctional, non-volatile additive that can regulate the growth of perovskite films and improve the efficiency and stability of perovskite solar cells (PVSCs).

During the experiments, the new additive boosted power conversion efficiency, reaching 24.8%, with an overall energy loss of 0.36 eV.

The unencapsulated devices also demonstrated improved thermal stability, maintaining 98% of their original efficiency after continuous heating at 65 ± 5°C for over 1,000 hours.

The team also found that this strategy could be applied to different perovskite compositions and large-area devices, highlighting its potential for fabricating scalable and highly efficient PVSCs.

The study was published in Nature Photonics under the title “Hydrogen-bond-bridged intermediate for perovskite solar cells with enhanced efficiency and stability.”

The researchers said this could pave the way for the widespread adoption of PVSCs in commercial applications.

Perovskite solar cells have emerged as a cost-effective and efficient replacement for conventional silicon-based solar cells. They can be deposited from solutions onto the fabrication surfaces, making them suitable for building-integrated photovoltaics, wearable devices, and solar farm applications.

However, the efficiency and stability of PVSCs are affected by defects present at the interfaces and grain boundaries of the perovskites, leading to severe energy loss.

Previous studies have focused on enhancing the morphology and quality of perovskite films using volatile additives.

However, these additives tend to evaporate from the film following annealing, forming a void at the perovskite-substrate interface.

The researchers at CityU said they addressed this challenge by adjusting the perovskite film growth to enhance the film’s quality.

The team discovered that adding a multifunctional molecule – 4-guanidinobenzoic acid hydrochloride (GBAC) – to the perovskite precursor creates a hydrogen-bond-bridged intermediate phase that alters the crystallization process.

This leads to high-quality perovskite films with large perovskite crystal grains and uniform grain growth from the bottom to the film’s surface.

Additionally, this molecule acts as a defect passivation linker that reduces the defect density of the perovskite film due to its non-volatility, resulting in significantly lower non-radiative recombination loss and improved film quality.

The researchers tested this approach by adding GBAC to the perovskite precursor and found that it significantly reduced the defect density of perovskite films and enhanced their quality.

Various organizations, including CityU, the Innovation and Technology Commission, the Research Grants Council, the Green Tech Fund of the Environment and Ecology Bureau in Hong Kong, the Guangdong Major Project of Basic and Applied Basic Research, and the Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials supported the study.

Last December, researchers from the Fraunhofer Institute of Solar Energy Systems (ISE) collaborated with industry partners to achieve an efficiency of 22.55% in a perovskite-silicon tandem solar cell measuring over 100 square centimeters.

Earlier in the month, scientists at the Swiss Laboratories for Material Science & Technology, Empa, claimed to have developed a low-temperature method using silver to produce a bifacial perovskite-copper indium gallium selenide tandem solar cell.