By Will Soutter
A team of scientists from the King Abdullah University of Science & Technology (KAUST) and University of Toronto (U of T) headed by Ted Sargent, an U of T Engineering Professor, has achieved a significant progress in the advancement of colloidal quantum dot (CQD) films, which in turn results in a CQD solar cell with an unprecedented efficiency of 7%.
The researchers have fabricated the solar cell from low-cost materials. They have described their work in the Nature Nanotechnology journal. Lead co-author, Dr. Susanna Thon explained that previously, the huge internal surface areas of the nanoparticles present in the film have been a limiting factor for quantum dot solar cells, thus making electricity extraction very difficult. In this work, the researchers have completely covered all the exposed surfaces by utilizing both organic and inorganic chemistry.
The fabrication of CQD films is rapid and inexpensive. This work opens the door to fabricate solar cells on flexible substrates just as the rapid printing of newspapers in mass quantities. The U of T solar cell demonstrates a 37% efficiency increase over the earlier certified record. To facilitate efficiency improvement, the researchers required a method to decrease the count of traps for electrons related to inferior surface quality, while concurrently ensuring denser films to capture maximum amount of light. The solution was a ‘hybrid passivation’ method.
Lead co-author, Alex Ip informed that the researchers covered the earlier inaccessible crevices that created the electron traps through the immediate introduction of tiny chlorine atoms subsequent to the synthesis of the dots. They then bonded quantum dots in the film tightly utilizing short organic linkers.
Work headed by Aram Amassian, a professor at KAUST, demonstrated the significance of the organic ligand exchange in achieving the densest films featuring the tightly-packed nanoparticles.
This work paves the way to optimize device efficiencies, which in turn leads to reliable and economical solar energy.