Growth of dandelion-shaped CuInSe₂ nanostructures by a two-step solvothermal process

CuInSe₂ (CIS) nanodandelion structures were synthesized by a two-step solvothermal approach. First, InSe nanodandelions were prepared by reacting In(acac)₃ with trioctylphosphine-selenide (TOP-Se) in 1-octadecene (ODE) at 170 °C in the presence of oleic acid. These InSe dandelions were composed of polycrystalline nanosheets with thickness < 10nm. The size of the InSe dandelions could be tuned within the range of 300nm-2νm by adjusting the amount of oleic acid added during the synthesis. The InSe dandelion structures were then reacted with Cu(acac)₂ in the second-step solvothermal process in ODE to form CIS nanodandelions. The band gap of the CIS dandelions was determined from ultraviolet (UV) absorption measurements to be ∼ 1.36eV, and this value did not show any obvious change upon varying the size of the CIS dandelions. Brunauer-Emmett-Teller (BET) measurements showed that the specific surface area of these CIS dandelion structures was 44.80m²g^-1, which was more than five times higher than that of the CIS quantum dots (e.g. 8.22m²g^-1) prepared by using reported protocols. A fast photoresponsive behavior was demonstrated in a photoswitching device using the 200nm CIS dandelions as the active materials, which suggested their possible application in optoelectronic devices.