Advancements in Perovskite-Based Solar Cells

What is it?

According to the United States Department of Energy, a perovskite solar cell is a crystal-structured material used in creating most photovoltaic (PV) solar cells, which are utilized in projects involving solar energy, such as solar panels. However, "perovskite" actually refers to a group of materials known for their potential high performance and low production cost. In such fields as energy, the type of perovskite that is used is one in particular, called “metal-halide perovskites” due to their composition of organic ions, metals and halogens. In energy applications, the most commonly used type is "metal-halide perovskites," which consist of organic ions, metals, and halogens. While perovskites are widely recognized in the energy sector, their versatile composition—some containing oxygen or being entirely inorganic—allows them to be applied in various other fields.

           These metal-halide perovskite’s main task is to absorb the light, exciting electrons, resulting in electricity being produced. The cells in which they are based are typically referred to as “thin-film”, as the layer of active perovskite required is much thinner than their silicone counterpart (“Perovskite”). It is common for both silicon and perovskite to be stacked on top of each other in order to boost absorption rates. Such cells are called “Tandem PV” cells as they work together to more efficiently collect and produce energy. Furthermore, several factors enhance the appeal of perovskites, including their resistance to imperfections in the crystal structure, their ability to convert light energy into electrical energy with comparable efficiency and speed to silicon, and their flexibility in engineering applications, allowing them to be integrated into various solar cells or modules and work well with other materials. However, the perovskite’s thin state is usually not an attractive feature in terms of its quality. Many attempts have been made to improve the quality of the films to reduce “interfacial nonradiative recombination due to defects and interface mismatch energy levels” (Chen et al.). In other words, higher quality film is needed to ensure the efficiency of transfer from light energy to electric, as perovskite is a light-absorbing material. To accommodate, different fabrication methods have been introduced as separate solutions. 

Currently, there are four commonly used methods in fabricating inverted perovskite solar cells. One such method is called Vacuum Deposition. During this process, the initial materials are “thermally evaporated” and introduced to each other to form perovskite crystals on top of a substrate (Chen et al.) Utilizing this method, it seems that the wettability of the substrate is negligible as the perovskite will form as usual, ensuring a dense and uniform film. One of the major advantages of using Vacuum Deposition is the control of the accuracy with film thickness. However, a downside to this method is the cost, as high energy consumption, complexity, and low material utilization are all heavy expenditures.

Another is called the Two-Step Solution Method. This method allows for a “more flexible modulation” of perovskite crystallization when compared to a simpler one-step method. However, this method in particular often creates excess lead iodide when utilized for creating planar structures and can serve as a blockade when interacting with the organic carbon used for creating the perovskite cells. In this way, the carbon only interacts with the top layer of the lead iodide, leaving the rest of the layer as residual, endangering the longevity of the cell. To address this problem, researchers have produced a method of recombining the excess lead through photolysis and an MAI solution to diffuse into the lead and control the thickness of the resulting cells. Additional engineering has also been introduced during the fabrication process in order to boost the collective efficiency of the solar cells. Efforts were made in order to decrease the number of defects, enhance stability, and increase quality of the film. One study utilized the natural additive of capsaicin to change the energetics of the perovskite surface, achieving an “impressive efficiency of 21.88% with a remarkable FF of 83.81%” (Chen et al.). However, capsaicin is not the only organic compound to be introduced as an additive. NH3+, organic ammonia cations, have also been broadly used for increasing efficiency and improving stability through the “organic moieties of the alkyl ligands,” which increased the overall crystallinity of perovskite films by “regulating the crystal growth orientation” (Chen et al.).

Impacts?

Since their introduction into solar cells in 2009, perovskite-based cells have been working in tandem with their silicone counterparts to lessen the impacts of non-renewable energy sources that are damaging to the environment. In particular, a group of scientists in Germany conducted a study on the life-cycle of perovskites within a tandem PV cell to determine the effects the technology would have on the sustainability of the solar energy and manufacturing sphere. According to the study, which analyzed the life-cycle of tandem PV cells rather than just the perovskite-based cell on its own, the production cost increased with the addition of silicon. Despite this, scientists discovered that “the additional energy required to manufacture a tandem module could be more than offset by the extra energy it will produce over its lifetime” (Hutchins). They also found that “the perovskite-on-silicon module has 6% to 18% less environmental impact than a silicon module” over a lifespan of about 25 years. This statistic alone contributes a great deal in the sustainability of perovskite in general, as the profits of energy largely outweighs the cost to produce. Moreover, as time goes on technology will continue to improve and increase the effectiveness of the tandem model. Oxford PV, a company established in Oxford, United Kingdom that focuses on developing perovskite-based solar technology, has improved the tandem cell efficiency mark up to 31%. 

Similarly, there has been a fair amount of improvement in other categories. Groups such as global warming potential, terrestrial ecotoxicity, freshwater consumption, fossil fuel depletion, and metal depletion have all been reported to be 7% higher impact in tandem modules specifically (Hutchins). A noteworthy advancement from Oxford PV’s model was constructed in 2023 by researchers at Helmholtz Zentrum Berlin (HZB) and certified by Fraunhofer Institute for Solar Energy Systems. This model was approved by the European Solar Test Installation and included a “conversion efficiency of 33.5% for silicon-perovskite tandem solar cells utilising commercial CZ silicon wafers” (Alsharif et al., 2024). It’s likely that the improvement of conversion efficiency will continue to rise in the coming years, thanks to the efforts of the researchers working to improve the current technology.

​​Advancements like these highlight the growing progress in technology and development, not only in response to potential crises like global warming, but also in the realm of scientific discovery. As scientists continue to research and experiment with perovskite technology, its effectiveness is bound to improve further. However, these improvements in solar energy technology are vital to reduce production cost so that decades of environmental damage can finally be halted. 

References 

Biju, Chen, Liu, Liu, and Qi, Yanqing. “Recent progress in the development of high-efficiency inverted perovskite solar cells.” NPG Asia Materials, 15, No. 27, 5 May 2023, doi:10.1038/s41427-023-00474-z. Accessed 29 January 2025.

Hutchins, Mark. “Environmental impacts of perovskite PV.” pv magazine, 11 July 2022, https://www.pv-magazine.com/2022/07/11/environmental-impacts-of-perovskite-pv/. Accessed 30 January 2025.

“Perovskite Solar Cells.” US Department of Energy, https://www.energy.gov/eere/solar/perovskite-solar-cells. Accessed 30 January 2025.

Alsharif, Beenarani, Elangovan, Kannadasan, Inamul, and Kim Mun-Kyeom. “Recent developments in perovskite materials, fabrication techniques, band gap engineering, and the stability of perovskite solar cells.” Energy Reports, vol. 11, pp. 1171-1190, June 2024, ScienceDirect, doi:10.1016/j.egyr.2023.12.068. Accessed 30 January 2025.