Field-Effect Passivation of the Cu₂O/ZnO Transparent Heterojunction Photovoltaic Device Using Ga₂O₃ Thin Film

Abstract

Photovoltaics (PV) would be more promising if light could generate electric power invisibly. This will endow more degrees of freedom to PV cells for wide-range deployment. Transparent photovoltaic (TPV) devices are the groundwork of the buildingintegrated photovoltaic (BIPV) systems that provide aesthetics to the buildings and solar energy convertor modules. TPV is adequate for the BIPV system of windows. Heterojunctions between p-type Cu 2 O and n-type ZnO have emerged as one of the most promising TPV devices. However, their inadequate transparency and a deficit of open-circuit voltage (V OC ) and shortcircuit current density (J SC ) remained an open challenge. In this work, we have fabricated a thin Ga 2 O 3 buffer layer embedded transparent ZnO/Cu 2 O heterojunction photovoltaic device, showing an average visible transmittance of more than 50%. The insertion of the Ga 2 O 3 buffer layer remarkably increases the J SC and V OC to ∼860% and ∼41%, respectively. The TPV device also demonstrated a high J SC of 3.41 mA/cm 2 under UV light. The Ga 2 O 3 layer provides a graded conduction band alignment and passivates the interface by the field-effect passivation mechanism. The Ga 2 O 3 buffer layer embedded device also demonstrated a broadband photodetection with remarkably high responsivity and detectivity of 250 mA/W and 5 × 10 11 Jones at self-biased conditions.