UV Visible spectra for S1, S2, S3 and S4 on glass and quartz

Band gaps are obtained from Tauc plots of UV-Vis spectra taken on a thin film of S1,2,3,4 on a glass substrate and band gap obtained from DRS via Kubelka-Munk function from a powder sample. The band gaps obtained from UV-vis Tauc plot and DRS Kubelka-Munk method are consistent with each other; we took the former to calculate the LUMO and cyclic voltammetry to calculate the HOMO energy levels. The band gaps obtained from thin films on a quartz substrate via UV-Vis Taiuc plots do not differ from the results for studies on a glass substrate, although the UV-Vis spectra obtained for the two substrates differ markedly. The indirect band gaps in the UV-vis Tauc plots correspond to the blue emission as expected for our materials.