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 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