Enhanced photovoltaic and piezo-photovoltaic effects in flexible oxide ferroelectric film directly coated on polyimide substrate

Flexible ferroelectric photovoltaic (FePV) films have drawn widespread attention. However, in addition to the low filling factor (FF) and large bandgap of ferroelectrics, the direct fabrication of oxide FePV film on polymer substrate is also a challenging research topic. Here, we demonstrate high-performance FePV devices can be obtained with partially crystallized Zn_0.92-xCu_x(Fe_0.04Li_0.04)O (ZCFLO) film directly coted on polyimide substrate utilizing a cheap and simple dip-coating method at low-temperature processing. By introducing the local ferroelectricity and the piezo-photovoltaic effect, enhanced carrier transportation is achieved in designed ferroelectric/amorphous nanostructures, and the photovoltaic performances of the ZCFLO devices are enhanced in broadened spectral range. Under the AM 1.5 G light and the tensile strain of 0.39%, the markedly improved FF (> 86%), large photoresponse (>15 mA/W), giant piezo-photovoltaic (PPV) tensor (∼1.94 mA∙W⁻¹∙GPa⁻¹) and resulted high PCE (>2.9%) were obtained in flexible ZCFLO (x = 0.05) FePV devices. This work not only offers a cost-efficient pathway to design high-performance FePV devices but also further broadens the research scope of piezo-phototronics.