Synthesis of CuInSe₂ nanocrystals using a continuous hot-injection microreactor

A very rapid and simple synthesis of CuInSe₂ nanocrystals (NCs) was successfully performed using a continuous hot-injection microreactor with a high throughput per reactor volume. It was found that copper-rich CuInSe₂ with a sphalerite structure was formed initially followed by the formation of more ordered CuInSe₂ at longer reaction times along with the formation of Cu₂Se and In₂Se₃. Binary syntheses were performed and the results show a much faster formation rate of Cu₂Se than In₂Se₃. The rate limiting step in the formation of CuInSe₂ is forming the In₂Se₃ intermediate. Rapid synthesis of stoichiometric CuInSe₂ NCs using a continuous-flow microreactor was accomplished by properly adjusting the Cu/In precursor ratio. Tuning the ratio of coordinating solvents can cause size differences from 2.6 to 4.1 nm, bandgaps from 1.1 to 1.3 eV, and different production yields of NCs. The highest production yield as determined by weight was achieved up to 660 mg/h using a microreactor with a small volume of 3.2 cm³.