Origin of photovoltaic effect in (Bi, Pb)2Sr2Ca2Cu3O10+δ/Ag heterostructure

We report I-V characteristics and remarkable photovoltaic effect of (Bi, Pb)(2)Sr2Ca2Cu3O10+delta/Ag (Bi-2223/Ag) heterostructure in the temperature range between 50 K and 340 K induced by purple-laser irradiation, which is closely related to the superconductivity of Bi-2223 and the charge transfer between silver electrode and the superconductor. Obvious photo-induced voltage has been observed in the whole temperature range with two polarity reversals at a critical temperature (T-pr1) above room temperature and at the superconducting transition temperature (T-c). A maximum value of the photo-induced voltage appears at the onset of superconducting transition temperature (T-m). We confirm that there exists a built-in electrical field at the interface of Bi-2223/Ag heterostructure, similar to that found in YBCO/Ag systems, which provides the separation force for the photo-induced electron-hole pairs. The origin of the built-in electric field below T-c is a result of charge diffusion or redistribution between silver and the superconducting Bi-2223 associated with the Proximity effect and Andreev reflection. The direction of the field is always pointing from the superconductor to the metallic electrode. Between T-c and T-pr1, the interface field pointing from metal to superconductor arises from the diffusion of electrons in the metal and holes in the superconductor. The additional polarity reversal of photo-induced open circuit voltage (V-oc) at T-pr1, which was not observed in YBCO/Ag system, implies a possible change of charge carrier type in Bi-2223. Our data provide a new dimension of information for depicting a more comprehensive picture of Bi-2223/Ag heterostructure and may lead to new applications of this high temperature superconductor in the field of photo-electronic sensing devices. (C) 2017 Elsevier B.V. All rights reserved.