Decarbonizing the electric grid is an important component of supporting net-zero economies. Canada has a legislated commitment to achieve net-zero greenhouse gas (GHG) emissions by 2050. Achieving this will require several deep decarbonization pathways including the use of solar and wind power for the electrification of our power grid.
Zhaoxin Zhang, an undergraduate student researching solar cells under Professor Jacob Krich’s supervision, is on a quest to make solar cells more efficient. A solar cell converts sunlight into electricity, and its efficiency is the portion of the energy in the sunlight that can be converted into electricity. The efficiency of the solar cells used in a photovoltaic system, in combination with latitude and climate, determines the annual energy output of the system. While most photovoltaics used today are made of a single semiconductor – silicon – new materials can in principle increase solar cell efficiencies by absorbing more sunlight while producing a higher voltage. These so-called intermediate band materials have been studied for twenty years, but none has yet produced a highly efficient solar cell.
Zhaoxin considered a new way to use these same intermediate band materials. While a standard intermediate band solar cell (IBSC) has the novel intermediate band material in the centre of the device, he considered the effect of moving the novel material to the rear, making a device called an electronically couple upconverter (ECUC). Using a combination of advanced MATLAB simulation and design principles guided by physics, Zhaoxin demonstrated that putting one of today’s imperfect intermediate band materials into an ECUC can achieve higher efficiency than putting the same material into an IBSC. His work is the first to analyze ECUC devices with realistically flawed materials, as we have today. He mapped out the solar cell efficiency that can be achieved using intermediate band materials with different band gaps and material quality, giving clear guidance to which materials have the greatest near-term potential.
In June 2021, Zhaoxin presented his research findings as a poster and manuscript at the 48th IEEE Photovoltaic Specialists Conference (PVSC). He hopes that someday photovoltaic technology will produce enough affordable sustainable energy to help mitigate the effects of climate change caused by GHGs. Zhaoxin attributes his success to the supervision and mentorship of Prof. Krich and the support that he received from the Krich research group. He received the Association of Professors of the University of Ottawa Student Award for 2019 and 2020 and is on the Dean’s honor list (2018-2021) with a CGPA of 9.92 for both the Department of Electrical Engineering and the Department of Physics. Zhaoxin is currently studying quantum information and preparing for graduate school at the University of Waterloo.
