Research groups such as Tokyo Institute of Technology have succeeded in developing semiconductors that show high conduction carrier mobility in both p-type and n-type using copper nitride.
Copper nitride is attracting attention as a new thin-film solar cell material because it is a semiconductor composed of only common elements and has a bandgap suitable for the sunlight spectrum and a high light absorption coefficient.However, it is difficult to produce high-quality crystals, and the characteristics as a semiconductor have not been clarified so far.
This time, the research group focused on the catalytic function of copper metal and devised a direct nitriding reaction of copper using ammonia and an oxidizing gas as a new nitride synthesis method.This made it possible to produce a high-quality copper nitride thin film, which was difficult in the past.The pure copper nitride thin film obtained by this method was an n-type semiconductor, which was a high-performance semiconductor with high electron mobility.
Semiconductors include p-type semiconductors in which holes are responsible for electrical conduction and n-type semiconductors in which electrons are responsible.In solar cells, high conversion efficiency can be obtained by combining p-type and n-type semiconductors made of the same material.
Therefore, in order to produce a p-type semiconductor, we attempted to design carrier doping based on first-principles calculations, and produced copper nitride to which fluorine ions, which were predicted to be effective, were added.When this was evaluated by observation with an atomic resolution electron microscope and electronic state analysis with emitted light, it was found that it was a p-type semiconductor, and its hole mobility was higher than that of gallium nitride, which is a typical nitride semiconductor. It showed a high value.
In this way, we have realized a high-quality copper nitride semiconductor that can produce both p-type and n-type.Since the synthesis method devised this time is suitable for large area and low cost, it is expected to be applied to inexpensive thin-film solar cells using p-type and n-type semiconductors of the same material.
Paper information: [Advanced Materials]] High-Mobility p-Type and n-Type Copper Nitride Semiconductors by Direct Nitriding Synthesis and In Silico Doping Design
