Synergistics of Cr(III) doping in TiO₂/MWCNTs nanocomposites: Their enhanced physicochemical properties in relation to photovoltaic studies

In the present investigation, optoelectronic modifications of the TiO₂ host lattice through insertion of Cr(III) (0.5–3.0 mol.%) as a dopant and thereafter its composites with MWCNTs prepared using single step in-situ sol-gel route and its photovoltaic performance of the hybrids was investigated using Ru(II) based sensitizer. The physicochemical properties (viz. structural, opto-electrical, morphological and charge transfer behavior) of the ternary Cr@TiO₂/MWCNTs NCs are compared with the TiO₂/MWCNTs NC through various spectroscopic (XRD, Raman, UV–Visible DRS, XPS, FT-IR, PL, TRPL and EIS measurements) and microscopic (HR-TEM with SAED) analysis. TRPL and EIS studies reveals that, average life time of the electrons in the excited state increases and interfacial charge transfer resistance decreases after the insertion of Cr(III) ion into the TiO₂ host lattice. After the detailed physicochemical investigations, binder free NCs were deposited on the F:SnO₂ (FTO) by doctor-blade technique using DMF and CH₃CN solvents and then anchored with N719 dye. Finally, sensitized photoelectrode sandwiched with Pt-counter electrode for making the sandwich dye sensitized solar cells (DSSCs) and photovoltaic performance of the assembled devices was measured under AM 1.5 solar simulator for I-V and IPCE measurements. The Cr_.0.010@Ti_0.990C NCs based DSSCs shows highest photovoltaic conversion efficiency up to η = 7.69% which is 20% (η = 6.18%) higher to that of undoped TiO₂/MWCNTs based DSSCs.