An innovative tunable photovoltaic electrochromic (PV-EC) device concept, in which planar distribution of silicon thin film solar cells (Si-TFSCs) structure with successively deposited electrochromic thin films (ECTFs) and electrolyte layer is demonstrated. The switching mechanism of a PV-EC device is realized by electrically separating the electrodes of the Si-TFSCs and ECTFs, and the connection of the two systems is achieved through an external switching apparatus that links each Si-TFSC and ECTF through one transparent conductive oxide (TCO) layer. According to the PV-EC device structure, Si-TFSCs arranged in stripes makes large area module fabrication feasible, while Si-TFSCs arranged in arrays allows pixel structure design possible. When illuminated by sunlight under short-circuit condition, the photopotential outputted from a single Si-TFSC drives ECTF layer to change color, simultaneously a portion of the photocurrent is stored in a capacitor. Once the ECTF is tinted, no power is needed to retain its colored state due to the bi-stable property of the electrochromic material. In order to revert the PV-EC device to its bleached state, the capacitor supplies reverse potential to cause discoloration of the ECTF. In addition, 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 a Si-TFSC module and as a self powered smart glass, which has great advantages in green energy application. (C) 2012 Elsevier B.V. All rights reserved.