Photovoltaic electrochromic device for solar cell module and self-powered smart glass applications

Abstract

An innovative concept of solution type photovoltaic electrochromic (PV-EC) device has been developed. The device includes a semi-transparent silicon thin-film solar cell (Si-TFSC) substrate, an electrochromic solution, and a transparent non-conductive substrate, wherein the electrochromic solution is located between the transparent non-conductive substrate and the Si-TFSC substrate. The solution type PV-EC device has at least the following advantages: (1) the electrodes in the PV-EC device are planarly distributed in the whole semi-transparent Si-TFSC substrate to create a uniform electric field, which makes large area PV-EC module application feasible; (2) since the PV-EC device can be driven with low voltage and low current, the demand for photopotential and photocurrent produced by the Si-TFSCs is lowered and thus the thickness of an intrinsic layer in each of the Si-TFSCs can be thinned, which increases the transmittance of the device, and (3) the electrical power generated by the PV-EC module can be controlled by an additional output switch layout coupled with the Si-TFSC. When illuminated by sunlight, a portion of electronic current produced by a Si-TFSC is converted into ionic current to cause color changing of the PV-EC device, while the monolithically integrated Si-TFSC module generates electricity to a connected load. In view of photoelectric conversion and optical modulation properties, the PV-EC device can both function as solar cell module and as self-powered smart glass, which has great advantages in green energy application.