Methods, employing a polycyclic hydrocarbon or a polycyclic heteroaromatic compound as sensitizers, are provided to increase the efficiency of removing, by irradiation, photolabile protecting groups that mask reactive sites on synthesis intermediaries. Preferred groups of photolabile protecting moieties include: ((.alpha.-methyl-2-nitropiperonyl)-oxy)carbonyl (MeNPOC), ((Phenacyl)-oxy)carbonyl (PAOC), O-(9-phenylxanthen-9-yl) (PIXYL), and ((2-methylene-9,10-anthraquinone)-oxy)carbonyl (MAQOC). In conjunction with using the sensitizers and protecting groups described above, a method of forming, from component molecules, a plurality of compounds on a support, each compound occupying a separate predefined region of the support is provided. These resulting solid-phase arrays are useful, for example, to assay for the presence of biochemical products in biological samples.