Shift Of Band Edge Research Articles

Light Harvesting and Optical-Electronic Properties of Two Quercitin and Rutin Natural Dyes

The photovoltaic properties of two dyes (quercitin (Q) and rutin (R)) were experimentally investigated. The results showed that Q had excellent photoelectric properties with J s c of 5.480 mA·cm−2, V o c of 0.582 V, η of 2.151% larger than R with J s c of 1.826 mA·cm−2, V o c of 0.547 V, and η of 0.713%. For a better understanding of the photoelectric properties of two molecules and illustrating why the performances of Q is better than R from the micro-level, the UV-VIs spectrum, Fourier transforms infrared (FT-IR) spectrum, and cyclic voltage current characteristics were experimentally investigated. What is more, density functional theory (DFT) and time dependent density functional theory (TD-DFT) have been implemented in theoretical calculation. Based on the calculated results, frontier molecular orbitals (FMOs), charge differential density (CDD), infrared vibration, first hyperpolarizability, projected density orbital analysis (PDOS), electrostatic potential (ESP), and natural bond orbital (NBO) were analyzed. Hole/electron reorganization energies ( λ h / λ e ), light harvesting efficiency (LHE), fluorescent lifetime (τ), absorption peak, and the vertical dipole moment ( μ n o r m a l ) were calculated, and the shift of conduction band edge of a semiconductor (ΔECB) has been analyzed, which has a close relationship with J s c and V o c . The results demonstrated that, due to the higher LHE, τ, μ n o r m a l , and red-shifted absorption peak, Q has better photoelectric properties than R as a promising sensitizer.

Insights into the Photoassisted Electrocatalytic Reduction of CO2 over a Two‐dimensional MoS2 Nanostructure Loaded on SnO2 Nanoparticles

AbstractPhotoelectrochemical reduction of CO2 to value‐added chemicals and fuels is an attractive strategy to store renewable energy and mitigate greenhouse gas emissions. In this study, based on the density functional theory (DFT) calculation, a two‐dimensional nanostructure MoS2 loaded on SnO2 nanoparticles (MS/SON) was prepared for photoassisted electrocatalytic reduction of CO2 to HCOOH through a two‐step process of facile hydrothermal and pyrolysis method. Through physical structure characterization and photoelectric performance test, the results indicated that the 5 % MS/SON exhibits exclusive HCOOH selectivity, the maximum FE is 43.8 %, the current density reached to 9 mA cm−2 at −1.4 V and the photocurrent value is 12.5 μA cm−2 under 0.5 V bias. The overpotential is as low as 245 mV. Besides, after the introduction of MoS2, there is a red shift in the adsorption band edge from 380 nm to 500 nm, indicating an enhancement of light response; the peak intensity of photoluminescence (PL) decreased, showing that the electron and hole are effectively separated; the values of electrochemical impedance spectroscopy (EIS) and Tafel plots (70 mV dec−1) were smaller than other ratios, demonstrating that the faster charge transfer rate; the proper introduction of MoS2 increased the specific surface area from 47.64 m2 g−1 to 55.99 m2 g−1, which was helpful to expand the number of active sites. It is demonstrated that MS/SON is an excellent CO2 reduction material.

Sharp contrast in the electrical and optical properties of vanadium Wadsley (VmO2m+1,m>1) epitaxial films selectively stabilized on (111)-oriented Y-stabilized ZrO2

Four oxidation states $({\mathrm{V}}^{2+},{\mathrm{V}}^{3+},{\mathrm{V}}^{4+},\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\mathrm{and}\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{5+})$ in vanadium oxides and the conversion between them have attracted attention for application to batteries and electronics. Compared to single-valence counterparts, however, there have been few reports on the fundamental properties of mixed-valence vanadium oxide films, as their complexity and closeness in thermodynamic phase diagrams hinder the formation of pure phases in film. Here, using an epitaxial growth technique with precise control of oxygen partial pressure (20--100 mTorr) on (111)-oriented Y-stabilized $\mathrm{Zr}{\mathrm{O}}_{2}$, we selectively stabilize pure phases of $\mathrm{V}{\mathrm{O}}_{2}(\mathrm{B})$ $(m=\ensuremath{\infty}), {\mathrm{V}}_{6}{\mathrm{O}}_{13}$ $(m=6)$, and ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$ $(m=2)$, so-called Wadsley phases $({\mathrm{V}}_{m}{\mathrm{O}}_{2m+1},mg1)$ in which ${\mathrm{V}}^{4+}$ and/or ${\mathrm{V}}^{5+}$ can coexist. Fractional increase of ${\mathrm{V}}^{4+}$ changes the electrical ground state, insulating $\mathrm{V}{\mathrm{O}}_{2}(\mathrm{B})$ and ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$, metallic ${\mathrm{V}}_{6}{\mathrm{O}}_{13}$ transition into insulators below 150 K. While $\mathrm{V}{\mathrm{O}}_{2}(\mathrm{B})$ and ${\mathrm{V}}_{6}{\mathrm{O}}_{13}$ exhibit strong spectral weights at low photon energy in the room-temperature extinction coefficients, the band-edge absorption shifts toward higher photon energy for smaller $m$, opening an indirect band gap of 2.6 eV in ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$. The sharp contrast of electrical and optical properties between vanadium Wadsley phases highlights the importance of precisely controlling the oxidation state of vanadium.

Oxygen vacancies and hydrogen doping in LaAlO3/SrTiO3 heterostructures: electronic properties and impact on surface and interface reconstruction

We investigate the effect of oxygen vacancies and hydrogen dopants at the surface and inside slabs of , , and / heterostructures on the electronic properties by means of electronic structure calculations as based on density functional theory. Depending on the concentration, the presence of these defects in a slab can suppress the surface conductivity. In contrast, in insulating slabs already very small concentrations of oxygen vacancies or hydrogen dopant atoms induce a finite occupation of the conduction band. Surface defects in insulating / heterostructure slabs with three overlayers lead to the emergence of interface conductivity. Calculated defect formation energies reveal strong preference of hydrogen dopant atoms for surface sites for all structures and concentrations considered. Strong decrease of the defect formation energy of hydrogen adatoms with increasing thickness of the overlayer and crossover from positive to negative values, taken together with the metallic conductivity induced by hydrogen adatoms, seamlessly explains the semiconductor-metal transition observed for these heterostructures as a function of the overlayer thickness. Moreover, we show that the potential drop and concomitant shift of (layer resolved) band edges is suppressed for the metallic configuration. Finally, magnetism with stable local moments, which form atomically thin magnetic layers at the interface, is generated by oxygen vacancies either at the surface or the interface, or by hydrogen atoms buried at the interface. In particular, oxygen vacancies in the interface layer cause drastic downshift of the 3d eg states of the Ti atoms neighboring the vacancies, giving rise to strongly localized magnetic moments, which add to the two-dimensional background magnetization.

Hydrothermal synthesis of Fe[sbnd] and Nb-doped titania nanobelts and their tunable electronic structure toward photovoltaic application

One-dimensional (1D) oxide nanostructures have been widely investigated to find novel properties. The study prepared titania nanobelts doped with iron (Fe) and niobium (Nb) at ultralow concentrations by one-step hydrothermal synthesis and post-calcination, and explored their electronic structure by spectroscopic and electrochemical analyses. The Fe and Nb doping generated Ti3+ donor levels and trap states as well as induced band-edge shift. The doped nanobelts produced higher photocurrents and quantum efficiencies, when evaluated as anode materials in dye-sensitized solar cells. Formation of the shallow states exerts a major influence on charge carrier diffusion in titania nanobelts, because of their roles as photoactive sites to facilitate electron transport via hopping and trapping/de-trapping events. The Fe and Nb dopants have a synergistic effect in the electronic conduction by increasing electron density and lifetime. Results demonstrate a feasibility of using aliovalent substitution by co-dopants to tailor extrinsic 1D oxide semiconductors.

Напряженно-деформируемое состояние гетероструктуры In1-xGaxAs/GaAs

There are no models in use that would take into account the influence of internal deformations in strained structures on the key parameters of heterojunctions depending on the concentration of layer's components and thickness. The aim of the present paper is to determine the dependence of elastic strains and deformations and define changes in zone diagram of In1-xGaxAs/GaA structure depending of the concentration of components and thicknesses of layer and substrate. The paper features calculation of strains in In1-xGaxAs/GaA heterostructure at different correlations between the thicknesses of contacting semiconductors. The calculated values of conduction band edge shift and valence-band splitting in substrate and layer allow the authors to define the dependence between the alteration of band gap width in presence of deformation produced by the change of the thicknesses of layer and substrate and concentration of components. The authors arrive at the definition, according to which the stress-strained state of In1-xGaxAs/GaA heterojunction leads to remarkable changes in its energy band structure. The paper includes equation of the dependence of main parameters of the energy band zone diagram of heterojunction on concentrations of components and proportion of thicknesses. The selection of correlations between substrate and layer thicknesses gives possibilities for a forecast and, further, management of parameters of the zone diagram and, consequently, of electronic properties of In1-xGaxAs/GaA heterojunctions. As a result of the research, the calculation formula of band gap width changes can be seen as a basis for analysis of changes being subject to alterations in concentration of components and correlation between layer and substrate thicknesses in elastically strained heterostructure.

Strong modulation of optical properties in rippled 2D GaSe via strain engineering

Few-layer GaSe is one of the latest additions to the family of two-dimensional semiconducting crystals whose properties under strain are still relatively unexplored. Here, we study rippled nanosheets that exhibit a periodic compressive and tensile strain of up to 5%. The strain profile modifies the local optoelectronic properties of the alternating compressive and tensile regions, which translates into a remarkable shift of the optical absorption band-edge of up to 1.2 eV between crests and valleys. Our experimental observations are supported by theoretical results from density functional theory calculations performed for monolayers and multilayers (up to seven layers) under tensile and compressive strain. This large band gap tunability can be explained through a combined analysis of the elastic response of Ga atoms to strain and the symmetry of the wave functions.

Variation of the conduction band edge of (Lu,Gd)3(Ga,Al)5O12:Ce garnets studied by thermally stimulated luminescence

Abstract The shift of the conduction band (CB) edge for thirty different (Lu,Gd)3(Ga,Al)5O12:Ce compositions, with simultaneous variation in Lu/Gd and Ga/Al content was studied using thermally stimulated luminescence (TSL). Specific TSL peaks were related to impurities of Ta, Cr, Yb, Ti and Eu in Lu1Gd2Ga3Al2O12:Ce ceramics. The shift of Yb-related peak positions (in temperature and trap depth) with composition modification was investigated as well. In Gd-containing (Lu,Gd)3(Ga,Al)5O12 compositions a non-monotonous shift of the CB edge with increasing Ga content has been affirmed. The difference between thermal trap depths evaluated from our TSL experiments and optical trap depths obtained from the literature was explained by the role of lattice relaxation.

Enhancement of solar cell performance through the formation of a surface dipole on polyacrylonitrile-treated TiO2 photoelectrodes

Polyacrylonitrile (PAN) was adsorbed onto the TiO2 surface, and the resulting photoelectrodes were applied in dye-sensitized solar cells (DSSCs). The DSSC with the PAN-modified TiO2 showed an increase in its short-circuit current (Jsc) and a decrease in its open-circuit voltage (Voc), resulting in a 17% enhancement of its photovoltaic performance when compared to the reference cell. By incorporating PAN onto the surface of the TiO2, a surface dipole was formed, which induced a conduction band edge shift of the TiO2 in a positive direction. This shift led to a considerable improvement in the electron injection efficiency, and hence the Jsc.

Performance Regulation of Thieno[3,2-b]benzothiophene π-Spacer-Based D-π-A Organic Dyes for Dye-Sensitized Solar Cell Applications: Insights From Computational Study.

Dye-sensitized solar cells (DSSCs) have been widely investigated; however, the development of promising dye sensitizers is still appealing. In this work, we perform a detailed theoretical search for high-efficiency D-π-A organic dyes using density functional theory and time-dependent density functional theory calculations. Specifically, we perform geometric optimization, and electronic structure and absorption spectra calculations for isolated dyes for two thieno[3,2-b]benzothiophene π-spacer-based D-π-A organic dyes SGT129 and SGT130, which show significant efficiency difference, before and after binding to a TiO2 semiconductor. The calculation results reveal that the coplanar configuration between the electron donor and the π-spacer can enhance electronic communication efficiently, thus facilitating intra-molecular charge transfer from the electron donor to the acceptor groups in SGT130. The absorption spectrum of SGT130 broadens and is red-shifted owing to the decreased bandgap. The higher light-harvesting efficiency, favorable intra-molecular charge transfer, larger shift of the conduction band edge in the TiO2 semiconductor, and slower charge recombination between the injected electrons in the TiO2 conduction band and the electrolyte explain the superior efficiency of SGT130 over that of SGT129. Using SGT130 as the reference dye, we further design four novel dyes 1–4 by modifying the π-spacer with electron-rich and electron-withdrawing moieties. Judging from the theoretical parameters influencing the short-circuit current and open-circuit voltage, we found that all dyes would perform better than SGT130 in terms of the favorable interfacial charge transfer (ICT) and light-harvesting efficiency, as well as the larger shift of the TiO2 conduction band edge. Our theoretical research is expected to provide valuable insights into the molecular modification of TBT-based D-π-A organic dyes for DSSC applications.

Tuning the electronic structure of GeC/WS2 van der Waals heterostructure by electric field and strain: A first principles study

Van der Waals (vdW) heterostructures made by stacking two-dimensional (2D) materials, open up a wide landscape of possibilities in bandgap engineering, due to the distinct properties of the building layers and diverse stacking arrangements possible. In this work, ab initio calculations based on density functional theory were performed to systematically investigate the tuning of electronic properties of GeC/WS2 heterostructures by applying either a vertical external electric field or a biaxial strain. GeC/WS2 heterostructures exhibit a direct band gap and a type-II vdW heterostructure. The bandgap of GeC/WS2 heterostructure can be dramatically modulated by applying a vertical external electric field or a biaxial strain, and semiconductor-metal transitions are observed under high electric field and large strain. The change of band gap is due to the shift of band edges of the heterostructure due to the static electric field induced potential energy and strain induced deformation potential. Differences in the pattern of change style can be assigned to changes of the bands assigned to CBM and VBM. It is interesting to note that the shift of band edge by electric field is screened by a factor of 3.54 as compared to the electrostatic calculation. The deformation potential of the CBM consisted of W 5d orbital is −1.58 eV, and that of the VBM consisted of C 2p orbital is −0.01 eV. In addition, the optical properties of the heterostructure exhibit a significant enhancement compared to the constituent layers, which indicates improved light absorption. The above results suggest that GeC/WS2 vdW heterostructures can find applications as opto-electronic devices and efficient solar energy harvesting materials.

Characteristics of low-frequency noise elimination in a fluid-filled pipe of dark acoustic metamaterial type

The suppression and absorption of low-frequency noise for a fluid-filled pipe system has become a challenging task. Inspired by the properties of acoustic metamaterials, we construct a fluid-filled periodic pipe system, consisting of small-size short acoustic pipes mounted on a fluid-filled main pipe system equidistantly along the axial direction of main pipe. The short acoustic pipe is filled with fluid and gas, and the fluid section is connected to the main pipe that is filled with the same liquid. In such a periodic pipe system, an ultra-low frequency and ultra-broad band gap of acoustic waves can be generated, making the acoustic waves transmitting in the pipe system effectively attenuated within the band gap frequency range. Since the attenuation effects of the band gap on the low-frequency sound are so strong (the acoustic waves almost cannot be transmitted through the pipe system) that the periodic pipe system is referred to as a dark acoustic metamaterial (DAM)-type fluid-filled pipe system. The formation mechanism of the first band gap can be ascribed to the co-resonance of the short acoustic pipe array in the piping system, and this band gap is categorized as resonant-type BG (RBG). The contribution of short acoustic pipes is to introduce a low-frequency and large impedances spatially into the system, whereupon the transmitting waves will experience a tempestuously resonance in the pipe. As a result, the transmission of acoustic waves within the RBG is stopped. The second band gap in a higher frequency range is classified as Bragg-type band gap (BBG), since it is induced by the effects of interference between the incident, the reflected and the transmitted acoustic waves existing in the periodic units. The interference effect on the suppression of wave transmission is strengthened by the ceaselessly repeating uniform cells. The lattice constant change can bring in a modulation effects on both the BBG and the upper band edge of RBG. Increasing the volume of gas chamber in the short acoustic pipe will result in a shift of lower band edge of RBG towards the low-frequency range but has no action on the upper band edge; similarly, the augment of the liquid volume of the short acoustic pipe also lowers the band edges of RBG, however, bandwidth of the RBG will be reduced. A membrane may be used to physically separate the gas from the fluid in the short acoustic pipe, rendering the design more feasible to be realized in practical engineering. The installation of membrane will not change the low-frequency band gap properties of the DAM pipe. The obtained results show that the proposed design in this study may provide a new way to solve the defiant problem of noise control in the low frequency range for fluid piping systems.

Dual Liquid Junction Photoelectrochemistry: Part II. Open-Circuit Photovoltage Variations Due to Surface Chemistry, Interfacial Dipoles, and Non-Ohmic Junctions at Back Contacts

Dual-liquid-junction photoelectrochemistry and finite-element computational modeling quantified the effect on open-circuit photovoltage, Voc, of varying barrier heights at the back, traditionally ohmic contact to a semiconductor. Variations in experimental back-contact barrier heights included changes in the redox potential energy of the contacting phase afforded by a series of nonaqueous, metallocene-based redox couples that demonstrate facile, one-electron transfer and dipole-based band edge shifts due changes in the chemical species at the semiconductor surface. Variation in semiconductor surface chemistry included hydrogen-terminated Si(111) as well as methyl-terminated Si(111) that yields a shift in band-edge alignment of ∼0.3 eV relative to hydrogen termination. While methylation of n-Si improves Voc values at rectifying contacts, methylation at an ohmic contact has a deleterious impact on Voc values. We discuss the present experimental and computational results in the context of non-ideal semiconductor contacts.

Surface engineering of ZnO nanorod for inverted organic solar cell

Crystallinity and band offset alignment of inorganic electron acceptor play a vital role in enhancing the device performance of inverted organic solar cell (IOSC). In this report, homogenous and vertically-aligned chemical treated ZnO nanorods (ZNR) were successfully grown on fluorine-doped tin oxide (FTO) substrate via a fully-solution method. It was found that the morphology of ZnO was fine-tuned from truncated surface to tubular structure under both of the anionic (KOH) and protonic (HCl) treatment. An extraordinary defect quenching phenomenon and hyperchromic energy band edge shift were observed in 0.1 M KOH-treated ZNR proven by the highest (0 0 2) peak detection and the lowest defect density. Compared with the pristine sample, the 0.1 M KOH-treated ZNR device showed a remarkable improvement in power conversion efficiency (PCE) up to 0.32%, signifying the effectiveness of anodic treatment. The robust correlation between the dependency of chemical treated ZNR and the device performance was established. This work elucidates a feasible method towards efficient IOSC devices development.

Dispersion engineering and thermo-optic tuning in mid-infrared photonic crystal slow light waveguides on silicon-on-insulator.

In this Letter, the design, fabrication, and characterization of slow light devices using photonic crystal waveguides (PhCWs) in the mid-infrared wavelength range of 3.9-3.98μm are demonstrated. The PhCWs are built on the silicon-on-insulator platform without undercut to leverage its well-developed fabrication process and strong mechanical robustness. Lattice shifting and thermo-optic tuning methods are utilized to manipulate the slow light region for potential spectroscopy sensing applications. Up to 20nm wavelength shift of the slow light band edge is demonstrated. Normalized delay-bandwidth products of 0.084-0.112 are obtained as a result of dispersion engineering. From the thermo-optic characterization results, the slow light enhancement effect of thermo-optic tuning efficiency is verified by the proportional relationship between the phase shift and the group index. This work serves as a proof of concept that the slow light effect can strengthen light-matter interaction and thereby improve device performance in sensing and nonlinearity applications.

Mechanism of Hole Trap Passivation in CdSe Quantum Dots by Alkylamines

The mechanism by which alkylamines brighten CdSe nanoparticles is investigated by transient absorption and time-resolved photoluminescence spectroscopy. The main effect of the amine is to reduce the extent of surface hole trapping, which cannot be rationalized by a model in which the amine directly binds to and thereby passivates a surface trap site. An alternative mechanism is proposed wherein the absolute energies of the valence and conduction band edges shift to more negative redox potentials upon binding of the amine. This decreases the thermodynamic driving force for hole trapping or hole transfer to an adsorbed acceptor, 4-methylbenzenethiol. Amine binding also increases the thermodynamic driving force for electron transfer to an adsorbed acceptor, methyl viologen. The rates of charge transfer to these acceptors have been measured, and the differences in the rates before and after treatment with alkylamines are consistent with the proposed mechanism.

Enhanced visible-light photocatalytic oxidation capability of carbon-doped TiO2 via coupling with fly ash

A carbon-doped TiO 2 /fly ash support (C-TiO 2 /FAS) composite photocatalyst was successfully synthesized through sol impregnation and subsequent carbonization. The carbon dopants were derived from the organic species generated during the synthesis of the C-TiO 2 /FAS composite. A series of analytical techniques, such as scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), were used to characterize the properties of the prepared samples. The results indicated that C-TiO 2 was successfully coated on the FAS surface. Coupling between C-TiO 2 and FAS resulted in the formation of Si–O–C and Al–O–Ti bonds at their interface. The formation of Si–O–C and Al–O–Ti bonds gave rise to a positive shift of the valence band edge of C-TiO 2 and enhanced its oxidation capability of photogenerated holes as well as photodegradation efficiency of methyl orange. Moreover, the C-TiO 2 /FAS photocatalyst exhibited favorable reusability and separability. This work may provide a new route for tuning the electronic band structure of TiO 2 . The coupling between C-TiO 2 and FAS led to a positive shift of the valence band edge of C-TiO 2 , enhancing its oxidation capability of photogenerated holes and improving its methyl orange photodegradation efficiency.

Optical thermometry based on cooperation of temperature-induced shift of charge transfer band edge and thermal coupling.

A novel optical thermometry is put forward, based on the cooperation of temperature-induced red shift of the charge transfer band (CTB) edge of the vanadates and thermal population of the thermally coupled energy levels (TCELs). Particularly, temperature-dependent CTB of Sm3+ (Er3+) doped LuVO4 was investigated from 300 to 480 K. Then, under the excitation of 360 nm at which the excitation efficiency enhances with temperature due to the temperature induced red shift of the CTB edge, temperature-dependent emissions of the TCELs of Sm3+ and Er3+ were investigated. The results indicate that the emission from the upper-level in the TCELs exhibits a dramatic increase, along with the increase of temperature. High relative sensitivity of 4304/T2 was obtained, which is remarkably superior to the previous reported sensors, using the temperature-dependent fluorescence intensity ratio of TCELs. This suggests that the proposed strategy is a promising candidate for highly sensitive optical thermometry.

Phase optimization study of orthorhombic structured SnS nanorods from CTAB assisted polyol synthesis for higher efficiency thin film solar cells

Orthorhombic SnS nanorods were prepared from CTAB assisted polyol synthesis method at reaction temperature of 150 °C. In this method, the source (Sn, S) concentration ratio, CTAB concentration and reaction time were optimized to obtain single phase SnS as evident from Raman and XPS analyses. Crystal structure from XRD along with SAED pattern confirmed the formation of orthorhombic SnS structure. Morphological analysis from HR-TEM revealed the formation of SnS nanorods with improved homogeneity in size and shape by increasing the reaction time and CTAB concentration. The observed shift in the absorption band edge and absorption maxima by varying the CTAB concentration and reaction time is very well correlated with the morphological and chemical structural variations. Tauc plot shows the successful tuning of band gap value to 1.5 eV which is the optimum value of thin film solar cells, by varying the reaction time of sample with 0.025 M of CTAB. Electrical properties were studied from the Hall measurement which showed p-type conductivity for single phase SnS while n-type conductivity observed for mixed phases.

Comparative study of absorption band edge tailoring by cationic and anionic doping in TiO2

Abstract Titanium dioxide (TiO2) is one of the most favored metal oxide semiconductors for the use as photoanode in photoelectrochemical cells (PEC) splitting the water into hydrogen and oxygen. However, the major impediment is its large bandgap that limits its utilization as photoanode. Doping has evolved as an effective strategy for tailoring optical and electronic properties of TiO2. This paper describes the synthesis of undoped as well as iron (Fe, cationic) and nitrogen (N, anionic) doped nanocrystalline titanium dioxide by sol-gel spin coating method for solar energy absorption in the visible region. All the prepared thin films were characterized by X-ray diffraction and UV-Vis spectroscopy. Doping of both Fe and N into TiO2 resulted in a shift of absorption band edge towards the visible region of solar spectrum.