Ulsan National Institute of Science and Technology (UNIST) has increased the efficiency of a quantum dot solar cell, which converts sunlight into electricity using quantum dots, to 11.53 percent by combining quantum dots and organic polymers.
UNIST announced on April 23 that Professor Jang Seong-yeon of the Department of Energy and Chemical Engineering has developed a photovoltaic device that maximizes the performance of quantum dot solar cells by using organic polymers.
The research team explained that solar cells use a property that absorbs sunlight (photoactive layer) to create electrons and holes. When electrons escape from the photoactive layer, holes are formed as if they were formed in places where electrons were removed. At this time, electrons and holes move to the cathode and anode of the solar cell, respectively, leading to power generation. Therefore, in order to increase the efficiency of the solar cell, the number of electron-hole pairs must increase, and these must be transported well to the electrodes.
The research team switched one side of the quantum dot solar cell to an organic polymer to better create and transport holes. This is because the newly developed organic polymer has an excellent hole creating capability and prevents electrons and holes from recombining, thereby transporting holes to the anode.
Normally, a quantum dot solar cell combines electron-rich quantum dots (n-type quantum dots) and 'hole-rich quantum dots (p-type quantum dots). In this study, organic polymers are attached instead of p-type quantum dots. A solar cell was constructed by synthesizing it with a certain molecular weight in consideration of the chemical structure of monomers constituting a polymer, and bonding it to an n-type quantum dot. The efficiency of the resulting quantum dot solar cell was 11.53 percent higher than that of current p-type quantum dot-based devices (10.80 percent). In particular, the newly developed organic polymer material can be made through an easy solution process, so that it is possible to manufacture an entire solar cell device via a solution process at room temperature.
This research was selected as the back cover of the Feb. 24 edition of “Advanced Energy Materials,” an authoritative academic journal in the field of energy materials.