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 Cu2O 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 (VOC) and short-circuit current density (JSC) remained an open challenge. In this work, we have fabricated a thin Ga2O3 buffer layer embedded transparent ZnO/Cu2O heterojunction photovoltaic device, showing an average visible transmittance of more than 50%. The insertion of the Ga2O3 buffer layer remarkably increases the JSC and VOC to ∼860% and ∼41%, respectively. The TPV device also demonstrated a high JSC of 3.41 mA/cm2 under UV light. The Ga2O3 layer provides a graded conduction band alignment and passivates the interface by the field-effect passivation mechanism. The Ga2O3 buffer layer embedded device also demonstrated a broadband photodetection with remarkably high responsivity and detectivity of 250 mA/W and 5 × 1011 Jones at self-biased conditions.