Methods for preparing colloidal nanocrystal-based thin films
Methods of exchanging ligands to form colloidal nanocrystals (NCs) with chalcogenocyanate (xCN)-based ligands and apparatuses using the same are disclosed. The ligands may be exchanged by assembling NCs into a thin film and immersing the thin film in a solution containing xCN-based ligands. The ligands may also be exchanged by mixing a xCN-based solution with a dispersion of NCs, flocculating the mixture, centrifuging the mixture, discarding the supernatant, adding a solvent to the pellet, and dispersing the solvent and pellet to form dispersed NCs with exchanged xCN-ligands. The NCs with xCN-based ligands may be used to form thin film devices and/or other electronic, optoelectronic, and photonic devices. Devices comprising nanocrystal-based thin films and methods for forming such devices are also disclosed. These devices may be constructed by depositing NCs on to a substrate to form an NC thin film and then doping the thin film by evaporation and thermal diffusion.
1. A method of preparing a dispersion of colloidal nanocrystals (NCs) for use as NC thin films, the method comprising the steps of:
depositing a dispersion of NCs capped with ligands on a substrate; and
immersing the substrate with the deposited NCs in a solution containing chalcogenocyanate (xCN)-based ligands to exchange the ligands of the deposited NCs with the xCN-based ligands.
2. The method of claim 1 , further comprising the step of forming the dispersion of NCs into a NC thin film on the substrate.
3. The method of claim 2 , following the immersing step, further comprising the step of forming at least one additional NC thin film on the substrate.
4. The method of claim 1 , wherein the substrate is flexible.
5. The method of claim 1 , wherein the NCs are at least one of cadmium-based, zinc-based, lead-based, gold-based, or silver-based.
6. The method of claim 1 , wherein the steps are conducted at about room temperature.
7. The method of claim 1 , further comprising nanoimprinting the dispersion of NCs on the substrate.
8. The method of claim 7 , wherein the steps are conducted at about room temperature.