Self-powered electrochromic device is a kind of instrument that can change transmittance with the electricity converting from solar energy. To realise the dual functions of solar energy harvesting and transmittance changing in one material, a novel derivative of triphenylamine (4-((4-(dimethylamino)phenyl)(phenyl)amino)benzyl)phosphoric acid (Ph₂ABPA-Me₂) is designed and synthesized in this paper. 1H NMR, FT-IR and MS were used to characterize the structure of the compound. Working electrode was made by dissolving the compound in chloroform and then immersing titanium dioxide-coated fluorine-doped tin oxide glass in the solution for 24 h. Its spectroelectrochemical properties were investigated with a UV-vis-IR spectrophotometer and a potentiostat, which allowed us to acquire transmittance spectra under potential control in a solution of 0.1 mol/L lithium perchlorate in propylene carbonate. The experiment was carried out with three electrodes system in which A wire acted as reference electrode and Pt wire as counter electrode. The working electrode shows light yellow with relatively high transmittance at -1.5 V and dark green with low transmittance at +2.5 V. The maximum transmittance contrast between the two states is 64.2% at 629 nm. Meanwhile, to investigate the photovoltaic properties of Ph₂ABPA-Me₂, Ph₂ABPA-Me₂-based electrochromic devices were made by sandwiching the working electrode and Pt-based counter electrode together with electrolyte of Iodolyte AN-50. The photovoltaic properties were measured with a solar simulator under 1 sun AM1.5G illumination. Energy conversion efficiency of 0.32% was obtained, with short-circuit current density of 1.32 mA/cm², open-circuit voltage of 0.44 V and fill factor of 0.54. All the results mentioned above suggest that the compound has dual functions of electrochromism and photovoltaics. Compared with traditional photoelectrochromic devices with both a photovoltaic electrode and an electrochromic electrode, the dual functional Ph₂ABPA-Me₂-based electrochromic device shows properties of simple construction, cheap to make and friendly to environment, and thus may have potential applications in buildings, vehicles and numerous types of displays.