In a new study published in Advanced Materials, Purdue researchers have successfully constructed a new perovskite interlayer that exhibits both superior thermal and moisture stability in ambient conditions.

Perovskite solar cells (PSCs) are semiconducting materials that have become a strong candidate for future power generation. Used to create solar energy and other photovoltaic technologies, PCSs have delivered more than 25% of power conversion efficiency (PCE). “Enhancing the stability and lifetime of perovskite devices is necessary in order to realize the goal of commercialization for perovskite photovoltaics,” said Jiaonan Sun. “Today, the stability of commonly used hole transporting layers (HTL) is still a bottleneck for achieving the required lifetime.” 

Poly(triaryl amine) (PTAA) is a promising polymeric hole transporting material used in PSC applications, however, it’s hydrophobicity causes problematic interfacial contact with perovskite, limiting the device’s performance. Led by Dr. Letian Dou, Purdue researchers successfully constructed a uniform two-dimensional (2D) perovskite interlayer with conjugated ligands, between three-dimensional (3D) perovskites and PTAA to improve the power conversion efficiency and the interfacial adhesion of the devices. These increased-ion migration, energy barrier conformal, 2D coated unencapsulated devices with new ligands provide greater thermal and moisture stability in different environments.

Still, constructing 2-D perovskites atop of 3D with energy landscape management remains a challenge. Purdue researchers conducted a second study published in the June edition of Science Advances, where they designed a series of p-conjugated organic cations to construct stable 2D perovskites, and to realize delicate energy level tunability at 2D/3D heterojunctions. They found that conjugated ligand designs for 2D/3D heterojunctions improves band alignment and charge transport in perovskite solar cells, which offers opportunities to realize high efficiency, without using unstable HTLs. 

 “The conjugated cations can influence the electronic structures of 2D/3D heterojunctions as much as the inorganic materials. This is the overlooked component in 2D/3D heterojunctions, which can actually break the charge transfer barrier with conventional insulating cations.” said Ke Ma. “In combination with the stable hole transporting materials, we are expecting this strategy will remove the roadblock to achieving both stable and efficient solar cells.” 

The two studies were supported by the DOE EERE and were completed in collaboration with Purdue Postdoctoral Researchers Dr. Ke Ma, Dr. Jiaonan Sun, and Purdue chemical engineering undergraduate student Anika Bhoopalam. Purdue Chemical Engineering’s Dr. Brett Savoie and Purdue Department of Chemistry’s Drs. Jiangui Mei and Libai Huang were also key collaborators in the studies. Additional coauthors of this work are affiliated with University of Kentucky, Chemistry and Nanoscience Center, National Renewable Energy Laboratory and University of California, San Diego. 

News release about this patent: https://www.purdue.edu/newsroom/releases/2023/Q1/purdue-engineers-improve-solar-cell-efficiency,-stability.html