Microwave-assisted polyol synthesis of aluminium- and indium-doped ZnO nanocrystals

Microwave heating is applied to prepare suspensions of ZnO:In (IZO) and ZnO:Al (AZO) nanocrystals in diethylene glycol as a high-boiling multidentate alcohol (so-called polyol). Both n-doped zinc oxides are realized with high yields and in suspensions with solid contents up to 10 wt-%. These suspensions are colloidally stable for months. According to dynamic light scattering, scanning electron microscopy, transmission electron microscopy, X-ray diffraction patterns and Brunauer–Emmett–Teller analysis as-prepared particles turn out to be single crystalline with an average diameter of 10–15 nm, a near monodisperse size distribution, and a low degree of agglomeration. As-prepared samples exhibit high resistivities due to the adhesion of DEG as a stabilizer on the particle surface. Subsequent to specific thermal post-treatment resistivities of 2.0 × 10−1 and 5.7 × 10−1 Ωcm are obtained for IZO and AZO powders, respectively. As a proof of the concept, thin layers are deposited on glass plates using a simple solvent evaporation technique. Post-treated layers exhibit a visible transmittance of about 80% and resistivities of 2.1 × 10−1 Ωcm (IZO) and 2.6 × 10−1 Ωcm (AZO). The bandgap of post-treated powders and thin layers is calculated to 3.2 and 3.3 eV, respectively.

Graphical abstractNon-agglomerated and redispersible ZnO:Al (AZO) and ZnO:In (IZO) are prepared via a polyol-mediated synthesis as nanoscale transparent conductive oxides. Chemical, electrical and optical properties are investigated in detail.Figure optionsDownload full-size imageDownload as PowerPoint slide