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

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 building-integrated 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 short-circuit 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.