A new microwave-assisted synthesis route to produce doped ZnO nanocrystals in non-polar media for the design of IR emissivity modulation devices

• Fast microwave solvothermal synthesis (MSS) of AZO nanocrystals (NCs) • LSPR of doped NC gives absorption in the MWIR and LWIR wavelength. • MSS method produced larger particles than the conventional one. • Stable electrophoretic inks at 30 mg/mL of doped NCs. • Emissivity variations up to 8 % for AZO-based inks in LWIR. This study describes the microwave solvothermal synthesis (MSS) of aluminum-doped ZnO nanocrystals (NCs) in a non-polar solvent, namely a hydrocarbon solvent. These NCs are compared with those obtained by the conventional solvothermal method. Both methods resulted in NCs with similar morphologies and IR absorption properties. However, the MSS method produced larger particles than the conventional one. These NCs were utilized to formulate an electrophoretic ink, then embedded in an electrophoretic display unit. Such a device is capable of modulating its emissivity and its apparent temperature observed by a long wave infrared (LWIR) camera. When the electrophoretic device was switched between its reflective and emissive states, the difference in apparent temperatures reached 4.2 °C, corresponding to an emissivity variation of 8.4 % in the LWIR.