PbSe/PbS Quantum Dots

PbSe/PbS Quantum Dots List

PbSe/PbS quantum dots are tiny semiconductor particles with the size of three dimensions below 100 nanometers, belonging to the lead group of sulfur quantum dots. PbSe/PbS quantum dots are direct bandgap semiconductor materials with high absorption coefficient and narrow bandgap. The absorption and emission wavelengths of PbSe/PbS quantum dots can range from 800 nm to 3000 nm, which can cover the whole near-infrared band. Based on quantum size effect, the optical and electronic properties of PbSe/PbS quantum dots are completely different from their corresponding bulk materials. In addition, PbSe/PbS quantum dots have many other properties, including quantum confinement effect, surface effect, quantum tunneling effect, small size effect, Coulomb blocking effect, multiple exciton generation, and the others. With the advantages of multiple excitons generation, high light absorption and other good excitonic properties, PbSe/PbS quantum dots have become popular research subjects for many scientific researchers.

Applications:

With the excellent optoelectronic performances, PbSe/PbS quantum dots are widely used in optical components.

• Solar cell field: Due to the existence of multiple exciton generation effect, the external quantum efficiency of solar cells designed by PbSe/PbS quantum dots can be over 100% and up to 114%. Moreover, the performances of solar cells can be greatly improved by using PbSe/PbS quantum dots with well-distributed particle size.

Figure 1. An example of PbSe/PbS quantum dots applied in solar cell.

• The others: PbSe/PbS quantum dots are widely used in many other fields, such as infrared photodetectors, field effect transistors, flexible light-emitting devices, optical communication and the others.

Classification:

According to particle size distribution, PbSe/PbS quantum dots can be divided into narrow-distributed PbSe/PbS quantum dots and wide-distributed PbSe/PbS quantum dots.

• Narrow-distributed PbSe/PbS quantum dots: The particle size distribution of this type PbSe/PbS quantum dots is narrow, and the absorption and emission peaks of PbSe/PbS quantum dots are concentrated. Therefore, it is suitable for application in the field of optoelectronics.
• Wide-distributed PbSe/PbS quantum dots: The particle size difference of this type PbSe/PbS quantum dots is large, which is not conducive to the performance improvement of optoelectronic devices.

Production processes:

The preparation methods of PbSe/PbS quantum dots include "Heat injection method" and "Cation exchange method".

• Heat injection method: Heat injection method is a traditional preparation method. PbS quantum dots are usually synthesized using (TMS)₂S as a sulfur precursor, which is not only expensive but also highly toxic and environmentally unfriendly. As for the synthesis of PbSe quantum dots, TOPSe is usually used as the precursor of selenium and PbO, OA and ODE as the precursor of lead. In this method, the size distribution of PbSe quantum dots obtained is good, but the stability in the air is poor.
• Cation exchange method: In cation exchange method, CdS or ZnS quantum dots are used as sulfur precursors and CdSe or ZnSe quantum dots are used as selenium precursors. By exchanging Cd²⁺ or Zn²⁺ into Pb²⁺, PbS/PbSe quantum dots can be obtained.

Figure 2. An example of cation exchange method

References

1. Etgar L, Yanover D, Capek R K, et al. Core/Shell PbSe/PbS QDs TiO₂ Heterojunction Solar Cell[J]. Advanced Functional Materials, 2013, 23(21): 2736-2741.
2. Zhang J, Crisp R W, Gao J, et al. Synthetic conditions for high-accuracy size control of PbS quantum dots[J]. The journal of physical chemistry letters, 2015, 6(10): 1830-1833.