| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF-TuA |
| Session: | Thin Film Photovoltaics |
| Presenter: | Vaishali Batra, The University of Alabama |
| Authors: | V. Batra, The University of Alabama S. Kotru, The University of Alabama |
| Correspondent: | Click to Email |
Exploring the viability of alternate materials to increase efficiency of the solar cells, and to decrease the fabrication cost, has gained momentum in the past decade. Ferroelectric materials are one of those materials which have become a subject of intense research for future energy applications. These materials are well established in memory and MEMS industry and nowadays are being investigated to design photovoltaic (PV) devices. These materials show PV effect without a need of p-n junction as required in semiconductor devices. Additionally they exhibit bulk PV effect due to internal electric field originating from electric polarization. Of all the materials, lanthanum doped lead zirconate titanate (Pb0.95La0.05Zr0.54Ti0.46O3/PLZT) of perovskite type crystalline structure is considered to be promising ferroelectric material for solar cell applications. The practical realization of these devices requires high PV response which is still a challenge. In this work, an innovative method based on orientation control of PLZT thin films is used to improve the PV response.
Promoting (001) orientation and suppressing (110) orientation in the PLZT films is observed to improve the electrical and optical properties of these films. This work focusses on effect of varying thickness of PLZT films on their electrical and optical properties. The reflectance and band gap energies strongly depend on film thicknesses and are found to be in the range of 3.30-3.57 eV. AFM demonstrates the change in morphology and improvement in roughness with respect to orientation. The roughness in the films is observed to increase with the increase in film thickness in the range of 2.92 nm to 4.06 nm. Raman spectroscopy reveals the shift in longitudinal and transverse optical modes with the change in film thickness suggesting the change in ferroelectric phases and crystallinity in the films. The electrical properties were studied using the model for metal-ferroelectric-metal (MFM) heterostructures with Schottky contacts using Pt electrodes. High polarization, free carrier concentration and higher photovoltaic properties are obtained from thicker PLZT films. The photovoltaic efficiency is observed to increase by ~4-10 times by controlling the orientation of the films.