EAPSI: Illuminating fundamental material properties to enable highly efficient and inexpensive solar cells

Katahara John K, Seattle WA

Investigators

Abstract

The price of electricity generated from solar cells remains too high to be economically competitive with traditional fossil fuel sources in most regions of the US. To effect widespread adoption of sustainable energy technologies, it is imperative that new methods to fabricate inexpensive and high efficiency solar cells be discovered. This project will explore an exciting family of materials known as hybrid organic perovskites (HP), which have shown efficiencies as high as 20% through solution processing. In spite of their superlative performance, much of the fundamental optical and electronic properties of these materials remains unclear, and additional studies are necessary to shed light on avenues for further improvement in efficiency. Optical characterization of these materials will be conducted in collaboration with Professor Yoshihiko Kanemitsu, an expert in ultrafast spectroscopy, at Kyoto University in Kyoto, Japan. By depositing a layer of the HP on another solar cell material like Silicon or Copper Indium Selenide (CISe), one creates a tandem solar cell that can harness more sunlight and reach even higher efficiencies (>30%). Much of the literature on HP has focused on the lower bandgap (1.6 eV) Methylammonium Lead Iodide composition. However, to maximize the efficiency of a tandem HP-CISe solar cell, the bandgap of the HP must be higher. Previous research has shown that the bandgap may be tuned by replacement of Iodine with Bromine. This research will explore the fundamental optoelectronic properties and carrier dynamics of hybrid perovskites as Bromine composition increases. Specifically, this project will utilize the expertise and equipment of the Kanemitsu lab for femtosecond transient absorption spectroscopy (TAS) and photoluminescence lifetime experiments. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science (JSPS).