Described area system and computer program product for producing a point in time copy of source data. Also, a problem involved has been that even a failure of one light-emitting element causes the entire device to fail, making improvement of production yield difficult. The photoactive layer includes an electron acceptor and at least two electron donors. The sorbent can then be applied to oil to sorb six times its own weight in oil. The encryption keys include a random encryption key generated randomly and chain encryption keys generated sequentially by performing a Hash function on the random encryption key at least one time. Methods to fabricate of such devices and to program, to erase and to read the device are provided.