In mid-2018, the editor learned that an article [1] published in 2013 contained some redundancies when compared with an earlier publication from the same authors published in Materials Letters [2]. The Optics Express article [1] neither mentioned nor referenced the earlier published work [2].

Following this notification, The Optical Society’s Editorial Ethics Subcommittee investigated the matter in accordance with OSA Ethical Guidelines. It determined that the Optics Express article [1] violated those guidelines because it overlapped significantly with the earlier paper, reusing much of the introduction and Figs. 1, 3, 4 and 5 to introduce the ZnO/Cu₂O heterojunction system for PV application. Other aspects of the work, however, were new.

After careful consideration, the Subcommittee has determined that publication of this notice of redundant publication is the best course of action. The Subcommittee acknowledges the cooperation of the authors in addressing this matter and notifying the readership.