Electron-hole Recombination Process Research Articles

Non Radiative Processes in Phosphorene

ABSTRACTNovel 2D materials with interesting properties have been synthetized and characterized recently. In particular, unlike graphene, silicene or germanene, phosphorene has attracted a lot of attention because of its intrinsic band gap. This property allows for a wide range of applications where semiconductor thin films are traditionally used (e.g. electronics, optoelectronics, thermoelectrics). For each application, the device efficiency depends on how well an electrical current is extracted from the active materials, and depends on a variety of electron scattering processes. Some of these scattering processes can considerably improve or degrade device efficiencies. In this contribution we focus on non-radiative electron-hole pair generation and recombination processes, i.e. impact ionization (charge carrier multiplication) and Auger processes (charge carrier recombination). The rate of these processes is calculated from first principles and their effects on device operation are estimated.

Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics

As carriers slowly move through a disordered energy landscape in organic semiconductors, tiny spatial variations in spin dynamics relieve spin blocking at transport bottlenecks or in the electron-hole recombination process that produces light. Large room-temperature magnetic-field effects (MFE) ensue in the conductivity and luminescence. Sources of variable spin dynamics generate much larger MFE if their spatial structure is correlated on the nanoscale with the energetic sites governing conductivity or luminescence such as in co-evaporated organic blends within which the electron resides on one molecule and the hole on the other (an exciplex). Here we show that exciplex recombination in blends exhibiting thermally-activated delayed fluorescence (TADF) produces MFE in excess of 60% at room temperature. In addition, effects greater than 4000% can be achieved by tuning the device's current-voltage response curve by device conditioning. These immense MFEs are both the largest reported values for their device type at room temperature. Our theory traces this MFE and its unusual temperature dependence to changes in spin mixing between triplet exciplexes and light-emitting singlet exciplexes. In contrast, spin mixing of excitons is energetically suppressed, and thus spin mixing produces comparatively weaker MFE in materials emitting light from excitons by affecting the precursor pairs. Demonstration of immense MFE in common organic blends provides a flexible and inexpensive pathway towards magnetic functionality and field sensitivity in current organic devices without patterning the constituent materials on the nanoscale. Magnetic fields increase the power efficiency of unconditioned devices by 30% at room temperature, also showing that magnetic fields may increase the efficiency of the TADF process.

Hybrid Density Functional Study on Mono- and Codoped NaNbO3 for Visible-Light Photocatalysis.

Monodoping with Mo, Cr, and N atoms, and codoping with Mo-N and Cr-N atom pairs, are utilized to adjust the band structure of NaNbO3 , so that NaNbO3 can effectively make use of visible light for the photocatalytic decomposition of water into hydrogen and oxygen, as determined by using the hybrid density functional. Codoping is energetically favorable compared with the corresponding monodoping, due to strong Coulombic interactions between the dopants and other atoms, and the effective band gap and stability for codoped systems increase with decreasing dopant concentration and the distance between dopants. The molybdenum, chromium, and nitrogen monodoped systems, as well as chromium-nitrogen codoped systems, are unsuitable for the photocatalytic decomposition of water by using visible light, because defects introduced by monodoping or the presence of unoccupied states above the Fermi level, which promotes electron-hole recombination processes, suppress their photocatalytic performance. The Mo-N codoped NaNbO3 sample is a promising photocatalyst for the decomposition of water by using visible light because Mo-N codoping can reduce the band gap to a suitable value with respect to the water redox level without introducing unoccupied states.

Employing 4-methoxybenzoic acid interfacial-modification to enhance the photovoltaic performance of CdS quantum dot-sensitized solar cells

The effect of incorporating self-assembled monolayers of 4-methoxybenzoic acid (MBA) on CdS quantum dot-sensitized (QDSSC) solar cells based on ZnO nanorods was evaluated. The MBA was deposited on the ZnO photoanode, with the deposition time being a process variable. Photoluminescence spectra indicated that the MBA modification can suppress the photogenerated electron–hole recombination processes and presumably passivate the surface defects. The ultraviolet photoemission spectroscopy results prove that MBA forms an energy barrier at the interface of ZnO and CdS which may retard the back transfer of electrons. Overall the inclusion of MBA imparts a weak positive enhancement of the photovoltaic performance of these QDSSCs and this is an approach that may be developed to give stronger effects using alternative chemistries.

Anomalous temperature-dependent spin-valley polarization in monolayer WS2

Single layers of transition metal dichalcogenides (TMDs) are direct gap semiconductors with nondegenerate valley indices. An intriguing possibility for these materials is the use of their valley index as an alternate state variable. Several limitations to such a utility include strong intervalley scattering, as well as multiparticle interactions leading to multiple emission channels. We prepare single-layer WS2 films such that the photoluminescence is from either the neutral or charged exciton (trion). After excitation with circularly polarized light, the neutral exciton emission has zero polarization. However, the trion emission has a large polarization (28%) at room temperature. The trion emission also has a unique, non-monotonic temperature dependence that is a consequence of the multiparticle nature of the trion. This temperature dependence enables us to determine that intervalley scattering, electron-hole radiative recombination, and Auger processes are the dominant mechanisms at work in this system. Because this dependence involves trion systems, one can use gate voltages to modulate the polarization (or intensity) emitted from TMD structures.

Size effect on negative capacitance at forward bias in InGaN/GaN multiple quantum well-based blue LED

Size effect of InGaN/GaN multiple quantum well (MQW) blue light emitting diodes (LEDs), on electrical characteristics in forward bias voltage at high injection current in light emission regime, is observed to induce a substantial dispersion in the current density and normalized negative capacitance (NC) (i.e., capacitance per chip area). The correction of normalized NC by considering the LED p-n junction series resistance has been found to be independent of chip area size with lateral dimensions ranging from 100 µm × 100 µm to 400 µm × 400 µm. This fact, confirms that the inductive effect which is usually behind the NC apparition is homogeneously and uniformly distributed across the entire device area and hence the dispersive characteristics are not related to local paths. From the characteristics of NC dependence on temperature, frequency and direct current bias, a mechanism based on the electrons/holes charge carriers conductivity difference is proposed to be responsible for the transient electron-hole pair recombination process inducing NC phenomenon. Direct measurement of light emission brightness under modulated frequency demonstrated that modulated light output evolution follows the same behavioral tendency as measured in NC under alternating current signal modulation. Thus it is concluded that the NC is valuable information which would be of practical interest in improving the characteristics and parameters relevant to LED p-n junction internal structure.

Water Splitting: Ultrasmall Co3O4 Nanocrystals Strongly Enhance Solar Water Splitting on Mesoporous Hematite (Adv. Mater. Interfaces 18/2015)

In article 1500358, D. Fattakhova-Rohlfing, T. Bein and co-workers describe the preparation of ultrasmall dispersible Co3O4 nanocrystals and successfully apply them as a surface treatment to nanostructured hematite photoanodes in light-driven water splitting. The treatment with nanoparticles leads to a striking photocurrent increase, which is attributed to a suppression of surface electron-hole recombination processes on millisecond to second time scales. The cover image is designed by Christoph Hohmann, Nanosystems Initiative Munich (NIM).

Comparison of chemical and physical reduction methods to prepare layered graphene by graphene oxide: optimization of the structural properties and tuning of energy band gap

A systematic study to optimize the structural properties of graphene synthesized from modified graphene by both chemical and physical reduction methods were studied. In the chemical method, the two most common reducing agent hydrazine hydrate and sodium borohydride at different concentrations were used. In the physical method, two different samples were produced using a heat treatment at 200 °C in the presence of argon gas. Structural properties, morphology and functional groups of samples by SEM, TEM, XRD, FTIR, UV–Vis, PL and TGA were analyzed. The results show that graphene sheets have been produced in all methods. This study showed that modified graphene with hydrazine hydrate (3 ml per 100 mg of GO) has the best structural properties. The result of physical reduction method by heat treatment in argon gas showed the lowest energy gap among other samples. The PL emission spectroscopy showed the strong intensities at 500 and 600 nm due to the overlap of the second order emissions in the electron–hole recombination processes as results from different types of electronically excited states and physical reduction had minimum of intensity. The obtained graphene nano-sheets showed an energy band gap from 1.37 to 2.70 eV that is suggested as an application method in opening of the energy band gap. However, synthesized graphene by the chemical reduction method by hydrazine hydrate treatment has the better structure, but the physical reduction method is rapid and equally appropriate.

Study of binary and ternary organic hybrid CdSe quantum dot photodetector

The hybrid binary and ternary photodetectors (PDs) were fabricated from P3HT–PC71BM with CdSe quantum dot (QD) materials. The absorption spectra of P3HT:PC71BM (named as B1), P3HT:CdSe (B2) and P3HT:CdSe:PC71BM (T) active blended material were analyzed in the wavelength range from 350 to 800 nm. The current density–voltage characteristics of the device were measured in dark and under illumination for study of detector detectivities and the contact with electrode. The \({J_{{\text{under}}\,{\text{illumination}}}}/{J_{\text{dark}}}\) ratio at −0.5 V for PDs B1, B2 and T is 1.1 × 102, 1.9 × 102 and 1.8 × 103, respectively. The values of detectivity \(({D^*})\) for B1, B2 and T are 1 × 1010, 2 × 1010 and 7 × 1011 Jones, respectively. The \({D^*}\) for PD T is ten times in comparison with B1 and B2 PDs. The linear dynamic range (LDR) value for ternary device is more than double to both binary PDs. The absorption by CdSe QD increases the photon efficiency in the ternary detector, and at the same time the ternary detectors have high detectivity in broad spectral range. The responsivity of current to the light intensity exponent θ for detector B1, B2 and T is ~0.55, 0.55 and 0.62, respectively, which represents a complex process of electron hole generation, recombination and trapping within active material.

Visible Light-Induced Photoelectrocalalytic Degradation of 4-Nitrophenol on BiVO4/Carbon Nanotube Electrode

The 4-Nitrophenol (1-Hydroxy-4-nitrobenzene, 4-NP) has been appointed as hazardous waste and priority toxic pollutants by U. S. Environmental Protection Agency (EPA). The 4-NP is present in wastewater of several industries and it presents a carcinogenic characteristic. Therefore, efficiently and low cost process for wastewater treatment for 4-NP is necessary. On the other hand, great interests in photocatalysis have been focused on degradation of organic pollutants under visible light irradiation. Thus, the aim of this work was to develop a photoanode based in bismuth vanadate (BiVO4) and multi-walled carbon nanotubes (MWNT) for 4-NP photoelectrochemical degradation under visible-light. A three-electrode conventional electrochemical cell was used. The Ag/AgCl/Cl– sat, platinum and BiVO4/MWCNT/FTO were used as the reference, auxiliary and working electrode, respectively. BiVO4/FTO and BiVO4/MWCNT/FTO electrodes were prepared using polyethylene glycol (PEG 300) as precursor solution. The BiVO4 photoanodes were characterized by X-ray diffraction, diffuse reflectance and cyclic voltammetry. The photocatalytic activity of the electrodes was evaluated using a 150 W metallic vapor lamp as the light source. The degradation experiments were carried in a cell with 20 mL of 0.5 mol L– 1 Na2SO4 and 10 mg L– 1 4-NP under magnetic stirring. The current density of 5 mA cm– 2 was applied for 1h. The concentration of 4-NP was monitored by UV-vis spectrophotometry. The presence of characteristics diffractions peaks are in agreement with crystal structure of the type monoclinic scheelite. The bandgap energy estimated by diffuse reflectance experiments for BiVO4/FTO and BiVO4/MWCNT/FTO were 2.43 eV and 2.42 eV, respectively. These results also confirm the presence of monoclinic structure of BiVO4. Cyclic voltammetry experiments showed both anodic and cathodic photocurrent. The higher photocurrent was observed to BiVO4/MWCNT/FTO electrode, indicating that the carbon nanotube improve the change transfer in the photoanode and decreasing of electron-hole recombination process. UV-vis spectra of 4-NP before degradation experiments exhibited two characteristic absorption peaks at 319 nm (band I) and 227 nm (band II). Electrochemical degradation of 4-NP at BiVO4/MWCNT/FTO were observed decrease of 32.5 % (band I) and 34.6 % (band II) due to formation of hydroxyl radical that attack the 4-NP. Moreover, under photoelectrochemical conditions at BiVO4/MWCNT/FTO the UV-vis spectrum did not show the band II and reduction of 67.6 % of band I. This result is indicative that generation of electron-hole pair improved the formations of hydroxyl radical and also participates of mechanism the degradation. When the photoelectrochemical degradation was conducted using the BiVO4/FTO electrode, only reduction of 42.7 % at band I was observed. So, it is possible to conclude that occurred a synergic effect between BiVO4 and MWCNT which provides more efficiently decomposition of 4-NP. Therefore, photoelectrochemical technology allied with BiVO4/MWCNT and visible-light is suitable for removal of organic pollutants. Acknowledgments: FAPESP (2014/06704-2; 2013/07296-2), INCTMN 2008/57872-1 CNPq 573636/2008-7 and CAPES.

Valence state change and defect centers induced by infrared femtosecond laser in Yb:YAG crystals

The broad band upconversion luminescence in Yb3+:YAG crystal has been observed in experiments under the irradiation of focused infrared femtosecond laser. The dependence of the fluorescence intensity on the pump power shows that the upconversion luminescence is due to simultaneous two-photon absorption process, which indicates that the broad emission bands at 365 and 463 nm could be assigned to the 5d → 4f transitions of Yb2+ ions and the one at 692 nm could be attributed to the electron-hole recombination process on (Yb2+-F+) centers. The absorption spectra of the Yb:YAG crystal samples before and after femtosecond laser irradiation, and after further annealing reveal that permanent valence state change of Yb ions from Yb3+ to Yb2+ and (Yb2+-F+) centers have been induced by infrared femtosecond laser irradiation in Yb3+:YAG crystal.

Role of F in Improving the Photocatalytic Activity of Rh-Doped SrTiO3

In this study, the effect of F doping on the electronic structure and photocatalytic activity of Rh-doped SrTiO3 has been investigated using hybrid density functional theory as a tool. Although doping with only Rh significantly enhances the visible light activity, the photoconversion efficiency has been found to be poor. This is due to the Rh4+ state, which introduces localized unoccupied states above the valence band and promotes the electron–hole recombination process. Upon codoping with F, the localized states are found to be completely passivated. Analysis of Bader charge indicates the existence of the lower oxidation state of Rh in the (Rh, F)-codoped SrTiO3. The valence band maxima are elevated significantly due to strong hybridization of the O 2p orbital and Rh 4d orbital, resulting in band gap narrowing to 2.50 eV. The nature of the band structure of (Rh, F)-codoped SrTiO3 is found to be strongly dependent on the relative proportion of the dopant elements. 1:2 (Rh, F) codoping not only results in a clean band structure but also reduces the band gap by a larger extent (0.88 eV). In the case of 2:1 (Rh, F)-codoping, localized unoccupied states in the forbidden region are still present. Calculation of the defect formation energy indicates that the doping of Rh becomes more feasible in the presence of F. The relative locations of the band edge for both 1:1 and 1:2 (Rh, F)-codoped SrTiO3 are found to be suitable for the overall water splitting process. Hence, introduction of F is expected to enhance the photocatalytic activity of Rh-doped SrTiO3 under visible light due to narrowing of the band gap as well as lowering of the electron–hole recombination rate.

Influence of size and shape on the photocatalytic properties of SnO₂ nanocrystals.

Tuning the functional properties of nanocrystals is an important issue in nanoscience. Here, we are able to tune the photocatalytic properties of SnO2 nanocrystals by controlling their size and shape. A structural analysis was carried out by using X-ray diffraction (XRD)/Rietveld and transmission electron microscopy (TEM). The results reveal that the number of oxygen-related defects varies upon changing the size and shape of the nanocrystals, which eventually influences their photocatalytic properties. Time-resolved spectroscopic studies of the carrier relaxation dynamics of the SnO2 nanocrystals further confirm that the electron-hole recombination process is controlled by oxygen/defect states, which can be tuned by changing the shape and size of the materials. The degradation of dyes (90%) in the presence of SnO2 nanoparticles under UV light is comparable to that (88%) in the presence of standard TiO2 Degussa P-25 (P25) powders. The photocatalytic activity of the nanoparticles is significantly higher than those of nanorods and nanospheres because the effective charge separation in the SnO2 nanoparticles is controlled by defect states leading to enhanced photocatalytic properties. The size- and shape-dependent photocatalytic properties of SnO2 nanocrystals make these materials interesting candidates for photocatalytic applications.

A steady-state and time-resolved photophysical study of CdTe quantum dots in water.

The exciton generation and recombination dynamics in semiconductor nanocrystals are very sensitive to small variations in dimensions, shape and surface capping. In the present work CdTe quantum dots are synthesized in water using 3-mercaptopropionic acid and 1-thioglycerol as stabilizers. Nanocrystals with an average dimension of 4.0 ± 1.0 and 3.7 ± 0.9 nm were obtained, when 3-mercaptopropionic acid or 1-thioglycerol, respectively, was used as a capping agent. The steady-state characterization shows that the two types of colloids have different luminescence behavior. In order to investigate the electronic structure and the dynamics of the exciton state, a combined study in the time domain has been carried out by using fluorescence time-correlated single photon counting and femtosecond transient absorption techniques. The electron-hole radiative recombination follows the non-exponential decay law for both colloids, which results in different average decay time values (of the order of tens of nanoseconds) for the two samples. The data demonstrate that the process is slower for 1-thioglycerol-stabilized colloids. The ultrafast transient absorption measurements are performed at two different excitation wavelengths (at the band gap and at higher energies). The spectra are dominated in both types of samples by the negative band-gap bleaching signals although transient positive absorption bands due to the electrons in the conduction band are observable. The analysis of the signals is affected by the different interactions with the defect states, due to ligand capping capacities. In particular, the data indicate that in 1-thioglycerol-stabilized colloids the non-radiative recombination processes are kinetically more competitive than the radiative recombination. Therefore the comparison of the data obtained from the two samples is interpreted in terms of the effects of the capping agents on the electronic relaxation of the colloids.

Electro-pumped whispering gallery mode ZnO microlaser array

By employing vapor-phase transport method, ZnO microrods are fabricated and directly assembled on p-GaN substrate to form a heterostructural microlaser array, which avoids of the relatively complicated etching process comparing previous work. Under applied forward bias, whispering gallery mode ZnO ultraviolet lasing is obtained from the as-fabricated heterostructural microlaser array. The device's electroluminescence originates from three distinct electron-hole recombination processes in the heterojunction interface, and whispering gallery mode ultraviolet lasing is obtained when the applied voltage is beyond the lasing threshold. This work may present a significant step towards future fabrication of a facile technique for micro/nanolasers.

Ultrafast dynamics of free carriers induced by two-photon excitation in bulk ZnSe crystal

Semiconductor materials exhibiting large optical nonlinearities and ultrafast nonlinear response have received extensive attention because of their potential applications in optical limiting, all-optical devices, optical telecommunication, and so on. As a direct-gap II-VI bulk semiconductor, ZnSe crystal has been exploited as the nonlinear optical devices in the regimes of nanoseconds and picoseconds during the past years. Owing to today's fast advance of laser sources with ultrashort femtosecond pulse duration, it is possible to investigate the ultrafast optical nonlinearities in the bulk ZnSe crystal. In this paper, we experimentally investigate the ultrafast dynamics of free-carriers induced by twophoton excitation in the bulk ZnSe crystal. By performing open-aperture Z-scan experiments with 41 fs laser pulses at the wavelength of 532 nm under the condition of low excitation intensity, the two-photon absorption coefficient is measured. As the excitation intensity exceeds a critical value, the interplay between third- and fifth-order nonlinear absorption processes is observed. To evaluate the ultrafast dynamics of free carriers, we have carried out femtosecond time-resolved degenerate pump-probe measurements with the same laser system used for Z-scan experiments in different levels of pump intensities. It is shown that the transient absorption signals peaked at the zero delay is a linearly increasing function of pump intensity, indicating that the observed instantaneous nonlinear absorption is dominated by the interband two-photon absorption process. At moderate irradiance, the transient absorption signals obviously indicate two components, arising from the two-photon absorption-induced free-carrier absorption, which is equivalent to the fifth-order nonlinear absorption process. Under the excitation of relatively high pump intensity, the magnitude of the reduction of free-carrier absorption signal becomes faster, suggesting that the ZnSe crystal exhibits a new effect and causes a transmittance change of the probe light. The presumable reasons are as follows: intense irradiances will result in the increase of carrier concentration and the rise of the lattice temperature as well as the narrowing of the band gap in the ZnSe crystal, which accelerates the electron-hole interband recombination process. Accordingly, the electron-hole recombination time decreases. Furthermore, when the carrier concentration is larger than 1018 cm-3, the occurrence of the electron-hole plasma is significant. At the same time, the enhancement of the scattering among the carriers results in the reduction of the free carrier absorption cross section. In summary, it is found that the free-carrier absorption cross section decreases whereas the electron-hole recombination time becomes shorter in ZnSe crystal as the excitation intensity increases, owing to both the narrowing of band gap and the occurrence of electron-hole plasma.

Enhanced photovoltaic performance of QDSSCs via modifying ZnO photoanode with a 3-PPA self-assembled monolayer

A SAMs layer of 3-PPA with a phosphonic acid headgroup and carboxylic acid tailgroups has been used to modify the surface of ZnO nanorods photoanode in CdS quantum dots sensitized solar cells. Its effects on the photovoltic performance have been investigated in detail by adjusting the concentration and deposition time of 3-PPA. Especially, we utilize ultraviolet photoelectron spectroscopy to characterize the variation of band alignment after introducing 3-PPA layer in the solar cells. The results reveal that the 3-PPA not only suppress the electron-hole recombination process due to its passivation on the surface defects, but forms an energy barrier to efficiently retard the back transfer of electrons, which finally results in the enhancement of conversion efficiency of solar cells.

Hematite-based photoelectrochemical water splitting supported by inverse opal structures of graphene.

By coupling α-Fe2O3 with a 3D graphene inverse opal (3D-GIO) conducting electrode, the short diffusion length of carriers and low absorption coefficient in α-Fe2O3 for photoelectrochemical applications were successfully addressed. GIO was directly grown on FTO substrate under low temperature conditions, removing the need for a graphene transfer process. α-Fe2O3 nanoparticles (NPs) were hydrothermally deposited on the surface of GIO, creating α-Fe2O3/GIO. The photocurrent density of α-Fe2O3/GIO in water splitting reactions reached 1.62 mA/cm(2) at 1.5 V vs RHE, which is 1.4 times greater than that of optimized α-Fe2O3. The EIS and IPCE data confirm reduced electron-hole recombination and fast electron transfer processes due to the short distance between active materials and the conducting electrode in the α-Fe2O3/GIO system. Our result may pave the way for designing devices in advanced energy conversion applications as well as a high efficiency hematite-based PEC system.

Sacrificial hydrogen generation from aqueous triethanolamine with Eosin Y-sensitized Pt/TiO2 photocatalyst in UV, visible and solar light irradiation

In this paper, we have studied Eosin Y-sensitized sacrificial hydrogen generation with triethanolamine as electron donor in UV, visible, and solar light irradiation. Aeroxide TiO2 was loaded with platinum metal via solar photo-deposition method to reduce the electron hole recombination process. Photocatalytic sacrificial hydrogen generation was influenced by several factors such as platinum loading (wt%) on TiO2, solution pH, Eosin Y to Pt/TiO2 mass ratio, triethanolamine concentration, and light (UV, visible and solar) intensities. Detailed reaction mechanisms in visible and solar light irradiation were established. Oxidation of triethanolamine and formaldehyde formation was correlated with hydrogen generation in both visible and solar lights. Hydrogen generation kinetics followed a Langmuir-type isotherm with reaction rate constant and adsorption constant of 6.77×10−6molmin−1 and 14.45M−1, respectively. Sacrificial hydrogen generation and charge recombination processes were studied as a function of light intensities. Apparent quantum yields (QYs) were compared for UV, visible, and solar light at four different light intensities. Highest QYs were attained at lower light intensity because of trivial charge recombination. At 30mWcm−2 we achieved QYs of 10.82%, 12.23% and 11.33% in UV, visible and solar light respectively.

Enhanced photocatalytic degradation of methylene blue by reduced graphene-oxide/titanium dioxide/zinc oxide ternary nanocomposites

In this report, an attempt has been made to prepare reduced graphene-oxide/Titanium dioxide/Zinc oxide (rGO/TiO2/ZnO) ternary photocatalyst system via a facile two step solvothermal method and their results were compared with rGO/TiO2 and TiO2. The structural, morphological and optical properties were explored using X-Ray diffraction (XRD), Scanning electron microscope (SEM), Energy Dispersive Spectra (EDS), Raman and Photoluminescence (PL). SEM images noticeably present the 2D sheet morphology of GO, irregular spherical morphology of TiO2 and nanorods morphology of ZnO. XRD pattern depicted the formation of TiO2 anatase and wurtzite hexagonal structure of ZnO, which is highly desirable for photocatalysis application. Further, the results of Raman spectra are in good agreement with the XRD data. The PL spectra evidently revealed the quenching effect of electron–hole recombination process. The photocatalytic degradation of the system was investigated using a model dye methylene blue (MB). The efficiency of the ternary system was evaluated and compared using rGO/TiO2 and TiO2. The degradation efficiency of rGO/TiO2/ZnO, rGO/TiO2 and TiO2 was found to be 92%, 68% and 47% within 120min respectively. Our results will pave the way for the development of futuristic rGO based ternary nanocomposites for photocatalytic applications.