Efficiency improving of NEMS solar cell using piezoelectric nanowires

This paper presents a new structure of solar cells based on NEMS (Nano Electro Mechanical System) technology to eliminate dependence of cell to band gap energy and improve efficiency. In this paper, the process of converting solar energy to electrical energy using NEMS solar cell, which is able to convert the thermal to mechanical energy and then to electrical energy by changing the temperature and using direct piezoelectric effect, is investigated. Thus, unlike photovoltaic cells, these cells have ability to absorb the full spectrum of the sun’s radiation. Energy conversion is such that at first a two-layer cantilever with different thermal expansion coefficient (Al aluminum and SiO2 Silicon Oxide) is diverted by solar energy absorption, thus the solar energy is converted to mechanical energy. This structure is capable to receive heat energy from all spectrum of solar radiations. The mechanical oscillation of PZT (Lead Zirconate Titanate) nanowires, which are perpendicular to cantilever beams, is converted to electrical energy. The electrical voltage produced by the proposed structure is an alternating voltage with amplitude of 0.9 volts. Also, the efficiency of this proposed cell, which was introduced at first time and does not have a similar sample, is 40% which shows improved performance and much smaller size compared to previous works.