Tel Aviv University's School of Chemistry’s Professor Eran Rabani and Hebrew University Professors Oded Millo and Uri Banin have revealed how semiconductor nanocrystals can be made into conductors by doping them.
Prof. Rabani says that changing the electronic properties of semiconductor nanocrystals will be useful for applications including photodiodes, diodes, electric parts used in digital cameras, solar panels, and mobile phones.
Prof. Rabani explains that using the new technique, nanocrystals can be doped to generate both p and n type, which will help to manufacture solar panels that are efficient and inexpensive, he says. The details of the research have been recorded in the journal Science.
According to Prof. Rabani, doping nanocrystals electrically is a challenging task. The crystals are capable of eliminating dopants by themselves. He added that some of the synthetic doping processes at the nano-scale were difficult. Prof. Rabani explains that the solution was to devise a way to dope the nanocrystals without affecting their optical properties or drastically reducing their absorption capabilities..
These difficulties were avoided by performing diffusion controlled reactions at room temperature. When the crystals were immersed in a solution with the dopants, the impurities slow diffused into the nanocrystal.
The researchers determined the success of their doping procedure using a scanning tunneling microscope (STM). It has been found from the measurements that there was a change in Fermi energy of nanocrystals after doping, which impacted the electronic properties of electronic equipment. The results prove that the nanocrystals have been doped with p-type and n-type dopants, which make it useful for electronics devices with a pn junction, such as light emitting diodes and solar panels.
The researchers were also able to vary the optical properties, including the color range produced by the nanocrystals. The nanocrystal particles on doping could turn more blue or red in color. Prof. Rabani and his coworkers could develop a theory to clarify these observations.