Aging of electroluminescent ZnS:Mn thin films deposited by atomic layer deposition processes

Electroluminescent ZnS:Mn thin films were deposited by the atomic layer deposition (ALD) technique. The deposition processes were based on ZnI2 or ZnCl2 as the Zn source and Mn(thd)3 (thd=2,2,6,6-tetramethyl-3,5-heptanedionato) as the Mn source. The ZnI2 process was found to have a wide temperature range between 300 and 490°C where the growth rate was independent of the deposition temperature, which offers the possibility to select the deposition temperature according to the thermal stability of the dopant precursor without reducing growth of ZnS. The electro-optical measurements suggested that the amount of space charge was lower within the phosphors made with the iodide process, which resulted in higher efficiency of the “iodide” devices as compared to the “chloride” devices. Brightness and efficiency of the best iodide device after 64h aging were 378cd∕m2 and 2.7lm∕W, respectively, measured at 60Hz and at 40V above threshold voltage. Conversely, brightness and efficiency of the best chloride device aft...