A method is described for forming a partially transparent thin film solar panel by providing an array of unconnected holes in an opaque layer of the panel the holes being sufficiently small so that they are not discernable to the human eye and the light transparency factor caused by the holes being selectively controlled so that it can be graded in two dimensions by varying the size and/or spacing of the holes. A thin film solar panel with an opaque layer which is made partially transparent by providing an array of unconnected holes therein, the holes being sufficiently small so that they arenot discernable to the human eye and the light transparency factor caused by the holes being graded in one or two dimensions by variations in the size and/or spacing of the holes is also described together with a laser ablation tool for forming such a panel, the tool comprising a laser, a scanner for scanning a laser beam relative to the panel, focussing means for focussing the laser beam on the opaque layer and control means for selectively controlling the laser repetition rate, the scanning speed, the pulse energy and/or the focussing of the laser beam whereby the light transparency factor caused by the holes can be graded in two dimensions by varying the size and/or spacing of the holes.