If you are researching perovskite solar cells or are planning to do so, an article in a recent issue of the Journal of Photonics for Energy is a great resource, as it provides an excellent review of the recent major advances in the field.
The open-access article, “Pathways toward high-performance perovskite solar cells: review of recent advances in organo-metal halide perovskites for photovoltaic applications,” by four researchers from University of Toledo (USA) highlights the evolution of the “perovskite fever” in terms of device architecture, material deposition processes, and device engineering techniques.
The article reports that organic metal halide perovskite (OMHP) planar structures can be categorized as n-i-p, inverted p-i-n, and recently, mesoscopic p-i-n. To date, no perovskite photovoltaic (PV) devices with significant efficiency have been constructed on opaque substrates because the conventional deposition technologies for transparent conducting oxides (TCO) may lead to decomposition of the surface of the OMHP.
Schematic diagrams of perovskite solar cells in the n-i-p mesoscopic, n-i-p planar, p-i-n planar, and p-i-n mesoscopic structures.
The meso n-i-p structure is the most popular structure reported in the literature, with record efficiency value of 20.2%. The OMHP record solar cell efficiency is at 22.1%, held by the Korea Research Institute of Chemical Technology and certified by the US National Renewable Energy Laboratory.
The device performance of most thin-film solar cells is mainly determined by the film quality of the absorber. Critical issues include the deposition approach, precursor composition, processing condition, and additive control, all of which can greatly affect the crystallization and quality of the perovskite films.
The deposition approaches include: single-step solution deposition, two-step solution deposition, two-step vapor-assisted deposition, and thermal vapor deposition. The two-step solution deposition has been the most successful approach due to advanced engineering techniques with the best cell efficiency at 20.2%.
The advanced engineering techniques include an intermolecular exchange process involving the reaction between the lead iodide (PbI2)-dimethyl sulfoxide (DMSO) intermediate phases and the formamidinium iodide (FAI)-methyl ammonium bromide (MABr) contained solution.
COMMERCIAL VIABILITY IS THE GOAL
The crucial issues and challenges that limit the commercialization of perovskite-based PV remain. Long-term device stability during operation under stressed conditions (high humidity, elevated temperature, and intense illumination) has yet to be demonstrated.
The existence of the J−V hysteresis limits the standardized characterization of device performance. Environmental impacts during the manufacturing, operational, and disposal phases of perovskite solar cells are unclear, leaving concerns about the toxicity and contamination associated with the water-soluble lead compounds.
Although the complexity of the diverse material preparation methods and device architectures makes it more difficult to address these issues, recent progress has provided insights into these issues and the corresponding material properties.
The “perovskite fever” is expected to continue for some time, given the momentum within the research community. Whether the technology will reach commercial viability in the PV market, however, is a question that remains unanswered.
Lead authors Zhaoning Song and Suneth C. Watthage are PhD students at University of Toledo. Coauthors Adam B. Phillips and Michael J. Heben are professors at the Wright Center for Photovoltaics Innovation and Commercialization at Toledo. The article appeared in the April issue of the journal, in a special series on perovskite-based solar cells.
–Fatima Toor is an assistant professor at University of Iowa and a guest editor for a forthcoming special section on tandem-junction solar cells in the Journal of Photonics for Energy.