Impact of TiO2 buffer layer on the ferroelectric photovoltaic response of CSD grown PZT thick films

Chemical solution deposition technique has been utilized to grow polycrystalline PZT thick films on Pt/Ti/SiO2/Si and TiO2-buffered Pt/Ti/SiO2/Si substrates. Effect of thin TiO2 buffer layer on the structural, dielectric and electrical properties of PZT films has been investigated in the present work. Polycrystalline single-phase PZT thick film is achieved using the buffer layer of TiO2. The disappearance of cracks in PZT films deposited on TiO2/Pt/Ti/SiO2/Si substrate indicates the role of the buffer layer as a diffusion barrier for platinum into PZT. The dielectric constant of the PZT film is found to be increased from 104 to 403, while the dielectric loss is reduced from 0.19 to 0.06 at 1MHz using the buffer layer of TiO2. Reduction in the leakage current density from 4.45x10(-5) to 2.42x10(-10) A/cm(2) is obtained for the titanium dioxide buffer layered PZT film. The saturation polarization (P-s = 45 mu C/cm(2)) is achieved for the optimized TiO2-buffered PZT thick film. Optimized PZT film shows well-defined butterfly loop revealing its ferroelectric nature. Free carrier concentration of the optimized film is determined from the Mott Schottky analysis and found to be 4.28x10(19) cm(-3). The ferroelectric photovoltaic device is fabricated using the optimized PZT thick film, and photovoltaic measurements are done under UV illumination with variation in UV intensity from 2 to 24 mW/cm(2). Short circuit current (I-sc) increased from 1.42 x 10(-9) to 0.63 x 10(-7) A with increase in the UV intensity from 2 to 24 mW/cm(2). However, open circuit voltage (-1.7V) is observed to remain constant with increase in the UV intensity 2 mW/cm(2) to 24 mW/cm(2), respectively. The power conversion efficiency is found to be increased from 0.15 to 0.58% with increase in the UV intensity from 2 to 24 mW/cm(2). The transient photocurrent is increased from 1.80 x 10(-9) to 1.57x10(-7) A with increase in the UV intensity from 2 to 24 mW/cm(2) at fixed DC bias voltage (5V) for the fabricated photovoltaic device. Response of the optimized fabricated photovoltaic cell to the incident UV light of different intensities is fast with excellent stability. A significant enhancement in the photocurrent from 1.68x10(-7) to 4.98x10(-7) A is found with heating along with UV illumination (intensity =24 mW/cm(2)).

Automated summary

Chemical solution deposition technique was used to grow polycrystalline PZT thick films on different substrates with and without a TiO2 buffer layer, showing significant effects on the structural, dielectric, and electrical properties of the PZT films. The optimized TiO2-buffered PZT thick film demonstrated improved dielectric properties and reduced leakage current density. Furthermore, a ferroelectric photovoltaic device fabricated using the optimized PZT thick film exhibited increased power conversion efficiency and stability under UV light of varying intensities.