FIG. 8a illustrates a method 800 for formulating the electroluminescence layer. Step 630 from method 600 comprises the method 800 and its steps. Method 800 commences at step 802. Step 802 comprises providing a water borne polyurethane. The urethane compound may be provided in a liquid form. Step 804 comprises adding ZnS powders and the hydroxylated BN nanosheets into the urethane liquid. In this example approximately 1 g of ZnS powder is used and 0.3 g of BN nanosheets were used. The BN nanosheets and ZnS are preferably formed using any suitable method. The urethane liquid may be hydrophilic. Step 806 comprises stirring the mixture for a set time e.g. 6 hours to obtain a uniform dispersion of ZnS powders and BN nanosheets. Step 808 comprises pouring the mixture into one or more moulds. The moulds may be glass moulds. Step 810 comprises placing the mould into an oven to cure at a set temperature and a set time. The set temperature in this example is 40 degrees Celsius and the set time is 12 hours. The curing causes water to evaporate from the polyurethane (PU) matrix. The curing forms a composite material that is the electroluminescence layer. The electroluminescence layer is sandwiched within two electrodes.