New quantum dot approach can improve 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 quickly increase the electrical conductivity of solar cells. The results were published in the journal Small.

The team identified a method for improving electrical conductivity through the use of “pulsed” light that produces significant concentrated energy at regular intervals. This method could replace the heat treatment process that requires a lot 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 being researched for the development of next-generation solar cells. They can absorb a wide range of wavelengths of sunlight, including ultraviolet, visible light, near-infrared and short-wave infrared, and have low processing costs due to solution processing and excellent photoelectric properties.

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

However, when PbS quantum dots are exposed to light, heat, and moisture, 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 commercialize 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 short period of a few milliseconds. Traditional techniques for heat treating PbS quantum dot layers involve heating them to high temperatures for tens of minutes using hot plates, ovens, etc.

The “pulse heat treatment technique” proposed by the research team overcomes the shortcomings of the existing method by using strong light to complete the heat treatment process in a few milliseconds. This leads to the suppression of surface defects and the extension of the traveling life of charges (electrons, holes) that generate electric current. In addition, high efficiency is achieved.

“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 existing quantum dot heat treatment process,” said Professor Choi from the Department of Energy Science and Engineering at DGIST.

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

This research was carried out in collaboration with Professor Changyong Lim from the Department of Energy Chemical Engineering, Kyungpook National University and Professor Jongchul Lim from the Department of Energy Engineering, Chungnam National University.

Provided by DGIST (Daegu Gyeongbuk Institute of Science and Technology)