Seminar: Semi-monolithic tandem solar cell architecture for photoelectrochemical water splitting

M.S. Student
Department of Mechanical Engineering
University of Hawaiʻi at Mānoa

Abstract
Tandem devices are necessary architectures for unassisted photoelectrochemical water splitting because of their ability to maximize the power conversion efficiency and provide a high photo- voltage necessary to drive the reaction. The traditional tandem integration process involves a monolithic tandem stack where the wide bandgap top cell is grown onto the narrow bandgap bottom cell, which places limitations on material selection and fabrication processes due to restrictions such as deposition techniques and temperature. To overcome this challenge and provide flexibility in material selection and manufacturing processes, a semi-monolithic tandem device architecture is investigated.

The semi-monolithic tandem device architecture is a novel approach of tandem cell manufacturing aimed at providing cost-effective, scalable photoelectrochemical water splitting technology. This technique employs a lift off and transfer method to combine two independently processed cells into one cell architecture using a transparent conductive adhesive (TCA) to create a multi-junction photovoltaic stack. This allows combination of materials which a standard deposition technique would not allow due to bottom cell degradation during deposition.

In this communication, we report our latest results for semi-monolithic tandem devices research. Being an essential steppingstone in the semi-monolithic tandem manufacturing process, characterization of the relative conversion efficiency of a single junction solar cell before and after the lift off process was investigated. Continued efforts in integration are being pursued through various semi-monolithic tandem device architectures.

About the speaker
Kai Outlaw-Spruell received his BS in Mechanical Engineering in 2020 from the University of Hawai‘i at Mānoa where he is currently an MS student in the Department of Mechanical Engineering. His research focuses on semi-monolithic tandem solar cell devices for photoelectrochemical water splitting. He performs research under Dr. Nicolas Gaillard in the Thin Films Lab of the Hawaii Natural Energy Institute.