Now I know it is a bit hard for high school students to obtain apparatus for a first-hand investigation. Your research can be a first-hand investigation or a second-hand investigation of other people's data; they are both valid for depth studies. You could investigate modern devices that exploit the photoelectric effect. Devices such as silicon photocells (solar cells), or photodiodes used in fibre-optical communication, or perhaps electronic digital cameras (the light sensor array). They all depend on the photoelectric effect.