In situ one-step synthesis of CuInS2 thin films with different morphologies and their optical properties

CuInS2 (CIS) thin films with petal-like nanostructures were synthesized in situ on copper substrates through a facile, one-step solvothermal method using InCl3 and thioacetamide ethylene glycol solution. In order to reveal the growth mechanism of CIS petal-like nanostructures, we synthesized CIS thin films with different morphologies at various reaction times. CIS thin films had a petal-like nanostructure. The petal possesses the preferentially exposed (222) facet, which becomes bigger and thicker as the increase of the reaction time. CIS petal-like nanostructures exhibited excellent light absorption properties. The average light absorption value of CIS synthesized at a reaction time of 4 h reached to 96.5%, and the minimum light absorption value even reached to 92% for that synthesized at a reaction time of 10 h. The CIS petal-like nanostructures synthesized at a reaction time of 4 h exhibit a band gap of 1.58 eV, which is much larger than that of the corresponding bulk material (1.04 eV). Furthermore, the band gap of CIS petal-like nanostructure decreases with increasing reaction time due to the increased "petal" thickness. All these results showed that the light absorption properties and band gap of CIS petal-like nanostructures can be adjusted by controlling the reaction time, which also indicated the application advantages of CIS petal-like nanostructures in photovoltaic and photocatalysis.