By Kristen Abels

If you read last month’s article on Energy Past, Present, and Future: Solar Energy, you’ll know that development and widespread adoption of solar photovoltaic (PV) technology for electricity generation has been a process decades in the making. While it has taken upwards of 40 years for solar PV panels to get to where they are today in terms of efficiency, cost-effectiveness, and large-scale manufacturability, we now find ourselves on the verge of the next generation of solar cells [1]. Organic photovoltaic (OPV) and hybrid organic-inorganic ‘perovskite’ PV cells are two of these next generation technologies, and are some of the exciting focuses of the Turak Research Group in the Department of Engineering Physics at McMaster University. Dr. Ayse Turak and her team aim to revolutionize the way people use clean energy by making organic and perovskite solar PV devices less expensive, more accessible, and more flexible [2].

So, what makes these ‘next-generation’ solar cells special? Unlike the traditional solar cell made of silicon, OPVs are polymer-based (they’re made of plastic!) which offers potential for distinct advantages in terms of cost, ease, and energy-intensity of manufacturing in today’s ever-growing solar energy market [3]. Perovskites also hold transformational potential for large-scale solar deployment in the future. These materials are named for their particular crystallographic structure – in this case, their composition of a positively charged organic component, a positively charged inorganic metal component, and a negatively charged halogen component in a particular arrangement [3]. As Dr. Turak explains, these OPV and perovskite PV cells offer a number of advantages over the traditional silicon PV cell:

Form factor: Silicon is brittle and stiff, limiting traditional solar PV cells to a particular mode of fabrication and application; OPV and perovskite PV cells are thin and flexible, allowing for easy fabrication and a wide range of applications not achievable with silicon PV cells.
Ease of fabrication: The manufacture of silicon PV cells is a very energy intensive process, involving high-temperatures and specialized equipment. OPV and perovskite PV cells have the distinct advantage of improved processability; the thin film coatings of OPV solar cells can be prepared in liquid form and coated onto the cells at ambient temperature in a simpler and less expensive process compared to traditional solar cell production [4] [5]. Imagine simple ‘spray-on’ solar cells for electricity generation – these were first demonstrated with perovskite solar paints in 2014 [6]!
Operation in low-light and diffuse-light conditions: Silicon solar cells work very well in high-light conditions, but their power conversion efficiency drops off in low- or diffuse-light conditions. At these conditions, OPV and perovskite technologies can outperform silicon, offering the opportunity to expand the range of solar power applications.

These are just a few of the advantages that these next-generation solar cell technologies permit. Imagine solar roofs on cars and buses, solar roof tiles and siding on houses, and solar perovskite paints that can be sprayed onto walls – OPVs and perovskite PVs open the door to incorporating solar power into applications not previously thought possible with traditional silicon PV cells! Organic materials also have narrow absorption wavelengths, which make it possible to develop transparent solar cell coatings on windows that let visible light through while using ultraviolet or infrared light to generate electricity instead. Altogether, these next generation technologies have the potential to make solar a cheap and ubiquitous source of power in the clean energy landscape of the future. Some companies like Oxford PV already plan to sell tandem perovskite-silicon cells to the public in early 2022 [7].

Dr. Ayse Turak, a professor at McMaster University.

That said, there are still some hurdles to overcome for them to become competitive with current technologies, namely improving efficiency, long-term stability, and scalability in the manufacturing process [8]. For reference, commercially available silicon-based solar panels can achieve up to 22.6% power conversion efficiency [9]. To date, OPV technologies have shown lower, but still promising cell efficiencies (the most recent OPV certified efficiency was 18.2%) and encouraging lifetimes (>5,000 hours) [5] [10]. Since the first application of perovskites for solar cells in 2012, this class of materials has reached even higher efficiencies up to 25.5% in the lab-setting, as high as some second-generation solar cells that have been in development for over 40 years [1] [10]! Despite the higher efficiency compared to OPVs, perovskites also suffer from poor stability. Improving stability and manufacturability of these next-generation technologies are some of the key challenges that researchers in the Turak Group are tackling by taking advantage of the wide range of tunability achievable with organic materials and their interfaces.

The improvement of power conversion efficiencies of different types of solar cells over time, with a focus on emerging technologies. Original image can be found here [1].

By making these technologies less expensive, more accessible, and more flexible, Dr. Turak’s mission is to change the narrative on solar power from ‘why’ utilize these technologies to ‘why not?’ - even at lower power conversion efficiencies, they allow us to passively generate electricity from solar power in applications not thought possible before.

Needless to say, the work being done in the Turak Research Group and other labs around the world has the potential to be game-changing in the widespread adoption of solar PVs in the clean energy landscape of the future. In addition to the focus on OPV and perovskite PV research for conversion of sunlight to electricity, Dr. Turak and her team are also focused on organic light emitting diodes (OLEDs) for the reverse conversion of electricity to light! For more information about Dr. Ayse Turak and all of the exciting work taking place in her research group, visit the Turak Research Group website here.

If you are interested in learning more, sign up for the McMaster Energy Conference, where the Dr. Turak will be one of our Energy Executives Panelists!

References

[1] “Perovskites Solar Cell Structure, Efficiency & More | Ossila.” [Online]. Available: https://www.ossila.com/pages/perovskites-and-perovskite-solar-cells-an-introduction [Accessed: 19-Feb-2021].

[2] Department of Engineering Physics, “Dr. Ayse Turak.” [Online]. Available: https://www.eng.mcmaster.ca/engphys/people/faculty/ayse-turak#overview. [Accessed: 19-Feb-2021].

[3] “Perovskite Solar Cells | Photovoltaic Research | NREL.” [Online]. Available: https://www.nrel.gov/pv/perovskite-solar-cells.html. [Accessed: 19-Feb-2021].

[4] G. F. Alapatt, R. Singh, and K. F. Poole, “Fundamental issues in manufacturing photovoltaic modules beyond the current generation of materials,” Adv. Optoelectron., vol. 2012, 2012, doi: 10.1155/2012/782150.

[5] “Organic Photovoltaic Solar Cells | Photovoltaic Research | NREL.” [Online]. Available: https://www.nrel.gov/pv/organic-photovoltaic-solar-cells.html. [Accessed: 19-Feb-2021].

[6] “Solar Paint: The Next Big Thing in Renewable Energy?” [Online]. Available: https://www.solarreviews.com/blog/solar-paint-hydrogen-quantum-dot-perovskite-solar-cells. [Accessed: 23-Feb-2021].

[7] M. Gallucci, “Perovskite Solar Out-Benches Rivals in 2021 - IEEE Spectrum,” 01-Jan-2021. [Online]. Available: https://spectrum.ieee.org/tech-talk/energy/renewables/oxford-pv-sets-new-record-for-perovskite-solar-cells. [Accessed: 27-Feb-2021].

[8] E. Spooner, “Organic Photovoltaics: An Introduction.” [Online]. Available: https://www.ossila.com/pages/organic-photovoltaics-introduction. [Accessed: 19-Feb-2021].

[9] “Most efficient solar panels 2021 — Clean Energy Reviews.” [Online]. Available: https://www.cleanenergyreviews.info/blog/most-efficient-solar-panels. [Accessed: 19-Feb-2021].

[10] M. Green, E. Dunlop, J. Hohl-Ebinger, M. Yoshita, N. Kopidakis, and X. Hao, “Solar cell efficiency tables (version 57),” Prog. Photovoltaics Res. Appl., vol. 29, no. 1, pp. 3–15, Jan. 2021, doi: 10.1002/pip.3371.

McMaster Spotlight: Next-Generation Solar Cells