Up to 10% Efficiency For Lead Free Quantum Dot Cells

• A new research work from Los Alamos National Laboratory sees good potential to scale up quantum dot technology for solar industry
• They have managed to get consistent photovoltaic performance with 85% photon-to-electron conversion efficiency
• Power efficiency level was discovered as up to 10% for zinc-doped cells by the team

Researchers at the Los Alamos National Laboratory in the US claim to have reached an efficiency level of 9% to 10% for a novel quantum dot solar cell without the presence of lead or other toxic elements. They were able to achieve a consistent photovoltaic performance with 85% photon-to-electron conversion efficiency.

This research work was published in the online scientific journal Nature Energy under the titled Spectroscopic insights into high defect tolerance of Zn:CuInSe₂ quantum-dot-sensitized solar cells.

For their work, the Los Alamos team used a reaction of copper, indium, and selenium adding zinc to make zinc-doped quantum dots while incorporating these into voids of a highly porous titania film that served as a charge collecting electrode. They explain that the quantum dots absorbed incident solar photons releasing tightly bound elements into a high-mobility conduction band. The electrons were then transferred to the titania electrode to produce a photocurrent.

"Due to their very complex composition (four elements are combined in the same nanosized particle), these dots are prone to defects," said Victor Klimov, lead author of the report and Los Alamos Physicist specializing in semiconductor nanocrystals. "Despite these imperfections, they showed nearly perfect performance in our solar cells—per each 100 absorbed photons we detected 85 photogenerated electrons, implying that the photon-to-electron conversion efficiency was 85%."

The research work sees these quantum dots with their defect tolerance and toxic element free composition along with photoconversion efficiencies as a promising material for 'implementing inexpensive, readily scalable and potentially disposable solar cells'.

Quantum dot cells are third-generation solar cells that that uses quantum dots as absorbing photovoltaic material in an attempt to replace typical bulk materials such a silicon, CIGS, CdTe. Unlike bulk materials, quantum dots have bandgaps that are tunable across a wide range of energy levels by changing their size. In bulk materials, the bandgap is fixed by the material chosen.