Multilayer Structures for Solar Energy Harvesting Applications

Photovoltaic materials are important in the design of solar cells for solar energy harvesting applications. Until recently the harnessing of solar energy has been performed primarily by silicon-based photovoltaic materials. Limitations in the intrinsic properties of silicon results in a need for additional materials to be studied in order to harvest solar energy with greater efficiency.

The authors used a ferroelectric non-centro-symmetric material to produce a photovoltaic effect known as the ferroelectric photovoltaic effect. This effect has been observed in bismuth ferrite, BiFeO3 (BFO). However, devices that use BFO thin films for photovoltaic applications have high leakage currents that degrades its multiferroic and hence photovoltaic properties. Barium titanate, BaTiO3 (BTO), is an equally interesting materials for use as a perovskite ferroelectric (FE) material but has a wide band gap (~3.3 eV). Efforts are continuously being made to reduce the optical band gap of BTO in order to retain the good ferroelectric properties in the visible region of light.

The authors have supposed that the use of multilayers of both these materials may overcome the failures of any one material for use in photovoltaic cells. To improve the ferroelectric properties of BFO while simultaneously reducing the band gap of BTO, fabrication of the multilayered structure of BFO and BTO could be beneficial. The authors had previously reported on the crystallographic, morphological and multiferroic properties of the BFO/BTO multilayer structures. A correlation between the structural and photovoltaic properties of the multilayer BFO/BTO structures demonstrated significant PV response owing to the preferred (110) growth and interface coupling induced strain between the adjacent layers. The BFO/BTO multilayer structure with six stacking layers exhibited maximum value of Voc = 1.80 V and JON/OFF = 2.955 × 103 at 405 nm due to good ferroelectric properties related to significant interface coupling between 6 stacking layers of BFO and BTO. Good retention and high stability of transient current response observed over multiple cycles of illumination (on and off) highlight the potential of the prepared photovoltaic cell based on 6 stacking layers of BiFeO3 and BaTiO3 and pave a way towards realization of new device functionalities in ferroelectric photovoltaic cell.

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The original full article can be found at De Gruyter here.
DOI: https://doi.org/10.1515/ehs-2016-0001
Energy Harvesting and Systems. 2016, 3 (3), 237–243.

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