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 improve the electrical conductivity of solar cells. The findings are published in the journal Small.

The team identified a method to improve electrical conductivity through the use of “pulse” light, which generates significant energy in a concentrated manner at regular intervals. This method could replace the heat treatment process, which takes 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 being researched for the development of the next generation of solar cells. They can absorb a wide range of sunlight wavelengths, including ultraviolet, visible light, near infrared and shortwave infrared, and have low processing costs due to solution processing and excellent photoelectric properties.

The manufacturing 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 on 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 surfaces can be accelerated, leading to charge recombination and deterioration of device performance. This phenomenon makes it challenging to bring these materials to market.

To suppress the formation of defects on the surface of PbS quantum dots, a team led by Professor Choi proposed a heat treatment in which the dots were exposed to light for a short period of several milliseconds. Conventional techniques for heat treating PbS quantum dot layers involve heating at high temperatures for tens of minutes using hotplates, ovens, etc.

The “pulse-type 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 results in the suppression of surface defects and the extension of the lifetime of charges (electrons, holes) that generate electric current. In addition, a high return is achieved.

“Through this research, we have been 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 DGIST’s Department of Energy Sciences and Engineering. .

“Moreover, 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 done in collaboration with Professor Changyong Lim of the Department of Energy Chemical Engineering of Kyungpook National University and Professor Jongchul Lim of the Department of Energy Engineering of Chungnam National University.

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