A new quantum dot approach could enhance the electrical conductivity of solar cells

A team led by Professor Jongmin Choi from the Department of Energy Science and Engineering has developed a PbS quantum dot that can rapidly enhance the electrical conductivity of solar cells. The results are published in the journal small.

The team identified a way to enhance electrical conductivity by using “pulse-shaped” light, which generates significant energy in a concentrated manner at regular intervals. This method can replace the heat treatment process, which requires a significant amount of time to achieve the same result. This approach is expected to facilitate the production and commercialization of PbS quantum dot solar cells in the future.

PbS quantum dots are nanoscale semiconductor materials that are actively researched for the development of next-generation solar cells. It can absorb a wide range of wavelengths of sunlight, including ultraviolet, visible light, near-infrared, and shortwave infrared, and has low processing costs due to solution processing and excellent photovoltaic properties.

The fabrication of PbS quantum dot solar cells involves several process steps. Until recently, the heat treatment process was considered an essential step because it effectively covers a layer of quantum dots on a substrate and heat-treats the material to increase its electrical conductivity.

However, when PbS quantum dots are exposed to light, heat, and humidity, the formation of defects on their surface can be accelerated, leading to charge recombination and degradation of device performance. This phenomenon makes it difficult to market these materials.

To suppress the formation of defects on the surface of PbS quantum dots, a team led by Professor Choi proposed a heat treatment that involves exposing the dots to light for a brief period of a few milliseconds. Conventional techniques for thermal treatment of PbS quantum dot layers involve heating them for tens of minutes at high temperatures using hot plates, ovens, etc.

The “pulse-type heat treatment technology” proposed by the research team overcomes the shortcomings of the current method by using strong light to complete the heat treatment process in a few milliseconds. This results in the suppression of surface defects and a prolongation of the transport life of charges (electrons and holes) that generate an electric current. Moreover, it achieves high efficiency.

“Through this research, we were able to improve the efficiency of solar cells by developing a new heat treatment process that can overcome the limitations of the current quantum dot heat treatment process,” said Professor Choi from the Department of Energy Science and Engineering at DGIST. .

“Furthermore, the development of a quantum dot process with an excellent multiplier effect is expected to facilitate widespread application of this technology to a range of optoelectronic devices in the future.”

This research was conducted in collaboration with Professor Changyeong Lim from the Department of Energy Chemical Engineering at Kyungpook National University and Professor Jungcheol Lim from the Department of Energy Engineering at Chungnam National University.