Enhanced photovoltaic response in ferroelectric Ti-doped BFO heterojunction through interface engineering for building integrated applications

The transparent nature of photovoltaic (PV) cell can replace the windows and facades in conventionally integrated buildings to harvest energy from natural sunlight and spontaneously generate electric power for various mankind applications. To demonstrate this idea, Ti-doped BiFeO3 (BFTO) lead-free ferroelectric material was explored as an active material in Pt/CuCrO2/BFTO/WS2/ITO PV cell where WS2 formed the n-type electron transport material (ETL), an unconventional p-type CuCrO2 was responsible for the hole-transportation (HTL) and bottom ITO and Pt top electrodes, were employed to extract the electrical properties of the device. A single heterojunction PV unit yielded a large short-circuit current density (JSC) and an open-circuit voltage (VOC) of 2.60 mA/cm2 and 0.95 V, respectively, which resulted in an improved efficiency of 100 orders or more as compared to the plain BFO based PVs. Different structural and absorption studies performed on 5% and 10% Ti-doped BFO revealed lower bandgap for 5% (2 eV) and thus higher absorption in visible region. The elevated ferroelectricity in 5% BFTO along with the indispensable driving force offered by ETL and HTL promoted enhanced band bending and thus efficient carrier separation and extraction in the heterostructure. A well-defined band diagram was proposed to explain the PV operating mechanism. For the integration of the transparent PV, a series connection of two 1 × 1 cm PV unit cells has been demonstrated to offer a significant amount of photogenerated voltage. This establishes the prospects of ferroelectric heterojunctions to realize PV power generation sources for emerging electronic applications.