Nanostructured metal oxides such as ZnO, TiO2, SnO2 and WO3 are essential in sensor applications due to their electrochemical properties and large chemically active surface. Tungsten (VI) trioxide (WO3) in particular, is a promising semiconductor due to its occurrence in different crystal structures (e.g., cubic, orthorhombic, monoclinic, etc.) with bandgaps in the range (~2.5−3.6 eV). However, WO3 has a low emission quantum yield at room temperature due to the non-radiative recombinations. Moreover, it has been reported that increasing the active surface of WO3 enhances its application potential. Another exciting aspect of WO3 is the oxygen vacancy-related photoluminescence centers. Electrochromic phenomenon (EC) is a phenomenon in which the optical properties (light absorption and emission) of materials change when counter balanced charges are injected or extracted from the material. WO3 is one of the most extensively studied electrochromic material and it is commonly used as an EC layer in smart windows. The EC of WO3 is found to depend on the type and concertation of impurities present in the lattice. It also depends on the concentration of oxygen vacancies. The stoichiometric WO3 has W6+ ions in the lattice. The presence of an impurity atom (electron donating) or an oxygen vacancy can create excess electrons in the lattice. These electrons can be localized on the 5d orbitals of W6+ cations. This leads to creating W5+ (in doped) or W5+ and W4+ (sub-stoichiometric) ionic states. Previously it was thought that the optical properties shown by WO3 are related to photoinduced charge hopping from W5+ to neighboring W6+ ionic states. Later reports tried to explain EC based on the polaron hopping due to the presence of lattice distortion. However, all these models could not explain the effect of oxygen vacancies on the EC characteristics of WO3. Recent publications suggest that oxygen vacancies play a crucial role in the occurrence of EC. The crystal direction in which the oxygen vacancy is formed is also important. This is because the bond length and angle can be different in the three crystal directions, for example in monoclinic WO3. The oxygen vacancies can exist in three different charge states and optical properties can be explained based on the transitions between v vacancy charge states. There are a lot of theoretical and experimental studies related to emission from the monoclinic WO3 phase. However, this is not the case with the orthorhombic phase of WO3. This project aims to synthesize and study the pure and doped orthorhombic phase of WO3 by different characterization techniques such as XRD, XPS, TEM, SEM, PL, UV-visible, etc. The high-temperature annealing of WO3 shows a structural phase transition from orthorhombic to monoclinic. The emission centers of the monoclinic structure are identified from the theoretical predictions of charge transition levels (CTL). We also show the experimental CTL, which can be used as a reference for the theoretical calculations of the orthorhombic phase. Al doping changes the bandgap and reduces emission intensity due to missing transitions compared to the undoped sample. This is attributed to the increased levels of non-radiative pathways in the doped samples.