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Doping is a unique strategy to modulate the optical and electronic properties of semiconducting materials. This study reports a facile approach to fabricate nitrogen-doped TiO2 (N-doped TiO2) photoanode for DSSC application. A solid-state reaction was employed to synthesize a series of N-doped TiO2 nanoparticles with different volumetric ratios of nitrogen dopant and the TiO2 host. The NH4OH as a nitrogen dopant was combined with P25-TiO2 via grinding followed by calcination at 500°C. The synthesized nanoparticles were extensively characterized by XRD, XPS, EDX, SEM, and TEM techniques. XRD results suggested that the incorporation of nitrogen had not altered the structure of the TiO2 lattice, and the presence of nitrogen was confirmed through the XPS and EDX spectroscopies. SEM and TEM images, obtained before and after N doping, showed that N-doped TiO2 nanoparticles with low amounts of NH4OH (10 and 20 μL) had retained their spherical shapes and sizes while use of higher amounts of the N dopant (30 and 40 μL) had led to agglomeration of nanoparticles. BET and BJH analyses revealed that the optimized N-doped TiO2 with 20 μL of NH4OH (20N-TiO2) possesses the highest average pore diameter of 15.99 nm. Furthermore, the UV-visible spectroscopic analysis confirmed a red shift in the optical absorption edge on N doping and the corresponding bandgap reduced from 3.15 to 2.94 eV with increase in the amount of NH4OH from 0 to 40 μL. Eventually, DSSCs were fabricated using the prepared pure TiO2 and N-doped TiO2 photoanodes, N719 dye, I − / I 3 − electrolyte, and Pt counter electrode, followed by investigating their performance under simulated irradiation with 100 mW/cm2 intensity with AM 1.5 filter. The photoanode doped with 20 μL of NH4OH (20N-TiO2) exhibited the highest power conversion efficiency (PCE) of about 6.16%, which was 20% higher than that of the control device, with improved J SC . This enhancement in J SC could be predominantly attributed to higher dye uptake along with marginal contribution by reduced rate of recombination. Among the reported studies on DSSCs with N-doped P25-TiO2 photoanodes, our method gives the best efficiencies for the DSSCs.

In this work, we propose and demonstrate a carbon nanotube (CNT) field-effect transistor (FET) based biosensor for selective detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). CNT FETs were fabricated on a flexible Kapton substrate and the sensor was fabricated by immobilizing the reverse sequence of the 25-base portion of the RNA-dependent RNA polymerase gene of the SARS-CoV-2 onto the CNT channel. The biosensors were tested for the synthetic positive and control target sequences. The biosensor showed a selective sensing response to the positive target sequence with a limit of detection of 10 fM. The promising results from our study suggest that the CNT FET based biosensors can be used as a diagnostic tool for the detection of SARS-CoV-2.

This study focuses on synthesizing the heavy metal-free ancient Egyptian blue (EB; CaCuSi4O10) dye using a facile ceramic method for luminescent solar concentrator (LSC) application. XRD, SEM and EDX results confirmed that this well-crystallized material is successfully synthesized. Optical studies revealed that EB has a high Stokes shift and possesses an average lifetime of 110.50 μs with a quantum yield of 12.93%. Finally, an EB-integrated LSC was fabricated that exhibits a power conversion efficiency (η) of 0.15% and an optical conversion efficiency (ηopt) of 1.21%, which are the highest values reported so far using EB. publishedVersion

This study reports a facile impregnation method for synthesizing Ni-doped TiO2 nanomaterials using P25-TiO2 as a starting material. The as prepared nanomaterials were subjected to structural and optical characterizations and subsequently employed in photovoltaic studies. X-ray diffraction (XRD) and Raman studies confirmed that Ni doping did not alter the anatase and rutile contents of P25-TiO2. Also, the presence of the constituent dopants and their ionic states were confirmed by Energy-Dispersive X-ray (EDX) and X-ray photoelectron (XPS) spectroscopies. Topographic Atomic Force Microscopic (AFM) images illustrated that Ni doping had increased the surface roughness of the TiO2. Optical characterization by UV-Visible spectroscopy revealed that the Ni doping had caused red shift in light absorption due to reduced TiO2 bandgap and improved the dye adsorption on TiO2 films. Then, the photocurrent–photovoltage property of the fabricated devices was investigated and the optimized 0.10 wt% Ni-doped TiO2 photoanode based device exhibited pronounced power conversion efficiency (PCE) of 6.29% under air mass (AM) 1.5 conditions (100 mWcm−2, 1 sun). Improved charge transport properties were also observed by the electrochemical impedance spectroscopic (EIS) study for the device with optimized Ni-doped TiO2 compared to the control device.

Perovskite solar cells (PSCs) composed of organic polymer-based hole-transporting materials (HTMs) are considered to be an important strategy in improving the device performance, to compete with conventional solar cells. Yet the use of such expensive and unstable HTMs, together with hygroscopic perovskite structure remains a concern – an arguable aspect for the prospect of onsite photovoltaic (PV) application. Herein, we have demonstrated the sustainable fabrication of efficient and air-stable PSCs composed of an invasive plant (Eichhornia crassipes) extracted porous graphitic carbon (EC-GC) which plays a dual role as HTM/counter electrode. The changes in annealing temperature (~450 °C, ~850 °C and ~1000 °C) while extracting the EC-GC, made a significant impact on the degree of graphitization - a remarkable criterion in determining the device performance. Hence, the fabricated champion device-1c: Glass/FTO/c-TiO2/mp-TiO2/CH3NH3PbI3−xClx/EC-GC10@CH3NH3PbI3−x Clx/EC-GC10) exhibited a PCE of 8.52%. Surprisingly, the introduced EC-GC10 encapsulated perovskite interfacial layer at the perovskite/HTM interface helps in overcoming the moisture degradation of the hygroscopic perovskite layer in which the same champion device-1c evinced better air stability retaining its efficiency ~94.40% for 1000 hours. We believe that this present work on invasive plant extracted carbon playing a dual role, together as an interfacial layer may pave the way towards a reliable perovskite photovoltaic device at low-cost.

Electrochemical energy storage has attracted much attention due to the common recognition of sustainable energy development. Transition metal sulfides and post-transition metal sulfides have been intensively been focused on due to their potential as electrode materials for energy storage applications in different types of capacitors such as supercapacitors and pseudocapacitors, which have high power density and long cycle life. Herein, the physicochemical properties of transition and post-transition metal sulfides, their typical synthesis, structural characterization, and electrochemical energy storage applications are reviewed. Various perspectives on the design and fabrication of transition and post-transition metal sulfides-based electrode materials having capacitive applications are discussed. This review further discusses various strategies to develop transition and/or post-transition metal sulfide heterostructured electrode-based self-powered photocapacitors with high energy storage efficiencies.

This study focuses on the fabrication and characterization of Cs2AgBiBr6 double perovskite thin film for field-effect transistor (FET) applications. The Cs2AgBiBr6 thin films were fabricated using a solution process technique and the observed XRD patterns demonstrate no diffraction peaks of secondary phases, which confirms the phase-pure crystalline nature. The average grain sizes of the spin-deposited film were also calculated by analysing the statistics of grain size in SEM image and was found to be around 412 (±44) nm the larger grain size was also confirmed by the XRD measurements. FETs with different channel lengths of Cs2AgBiBr6 thin films were fabricated on an electrode deposited heavily doped p-type Si substrate with a 300 nm thermally grown SiO2 dielectric under ideal conditions in air processing under ambient pressure and temperature. The Cs2AgBiBr6 FETs showed a p-type nature with a positive threshold voltage. The on current, threshold voltage and hole-mobility of the FETs decreased with increasing channel length. A high average hole mobility of 0.29 cm2s-1V-1 was obtained for the FETs with a channel length of 30 µm, and the hole mobility was reduced by an order of magnitude (0.012 cm2s-1V-1) when the channel length was doubled. The on current and hole-mobility of Cs2AgBiBr6 FETs followed a power fit, which confirmed the dominance of channel length in electrostatic gating in Cs2AgBiBr6 FETs. A very high-hole mobility observed in or FET that could be attributed to the much larger grain size of Cs2AgBiBr6 film made in this work.

This study focuses on the fabrication and characterization of Cs

This work focuses on the role of Lithium doped Poly(3-hexylthiophene)(P3HT) in metal-free quaterthiophene (4T) dye treated Titanium dioxide (TiO2) based hybrid solar cells. The dye treated hybrid solar cells with Lithium doped P3HT showed efficiencies (3.95%) of nearly a factor of four times higher than the pristine P3HT based control TiO2/4T/P3HT devices (1.04%). The enhancement of the efficiency is mainly due to highly efficient charge collection attributed to enhanced charge transport and light harvesting properties of Lithium doped P3HT polymer. The optimized solar cells with Lithium doped P3HT showed a high short circuit current density over 13 mA/cm2, under simulated irradiation of intensity 100 mW/cm2 with AM 1.5 filter. This significant increase in current density in TiO2/4T/doped P3HT solar cell is also confirmed by both the broadened External Quantum Efficiency spectrum and significant photoluminescence quenching upon replacement of pristine P3HT with doped P3HT on 4T dye treated TiO2 electrode. With Lithium doped Spiro-OMeTAD instead of Lithium doped P3HT, similar devices showed efficiencies over 3.30% under simulated irradiation of 100 mW/cm2 with AM 1.5 filter.

Titanium dioxide (TiO2) is a commonly used wide bandgap semiconductor material for energy and environmental applications. Although it is a promising candidate for photovoltaic and photocatalytic applications, its overall performance is still limited due to low mobility of porous TiO2 and its limited spectral response. This limitation can be overcome by several ways, one of which is doping that could be used to improve the light harvesting properties of TiO2 by tuning its bandgap. TiO2 doped with elements, such as alkali-earth metals, transition metals, rare-earth elements, and nonmetals, were found to improve its performance in the photovoltaic and photocatalytic applications. Among the doped TiO2 nanomaterials, transition metal doped TiO2 nanomaterials perform efficiently by suppressing the relaxation and recombination of charge carriers and improving the absorption of light in the visible region. This work reports the possibility of enhancing the performance of TiO2 towards Dye Sensitised Solar Cells (DSSCs) and photocatalytic degradation of methylene blue (MB) by employing Zn doping on TiO2 nanomaterials. Zn doping was carried out by varying the mole percentage of Zn on TiO2 by a facile solvothermal method and the synthesized nanomaterials were characterised. The XRD (X-Ray Diffraction) studies confirmed the presence of anatase phase of TiO2 in the synthesized nanomaterials, unaffected by Zn doping. The UV-Visible spectrum of Zn-doped TiO2 showed a red shift which could be attributed to the reduced bandgap resulted by Zn doping. Significant enhancement in Power Conversion Efficiency (PCE) was observed with 1.0 mol% Zn-doped TiO2 based DSSC, which was 35% greater than that of the control device. In addition, it showed complete degradation of MB within 3 h of light illumination and rate constant of 1.5466×10−4s−1 resembling zeroth order reaction. These improvements are attributed to the reduced bandgap energy and the reduced charge recombination by Zn doping on TiO2.

Earth–abundant transition metal chalcogenide materials are of great research interest for energy production and environmental remediation, as they exhibit better photocatalytic activity due to their suitable electronic and optical properties. This study focuses on the photocatalytic activity of flower-like SnS2 nanoparticles (composed of nanosheet subunits) embedded in TiO2 synthesized by a facile hydrothermal method. The materials were characterized using different techniques, and their photocatalytic activity was assessed for hydrogen evolution reaction and the degradation of methylene blue. Among the catalysts studied, 10 wt. % of SnS2 loaded TiO2 nanocomposite shows an optimum hydrogen evolution rate of 195.55 µmolg−1, whereas 15 wt. % loading of SnS2 on TiO2 exhibits better performance against the degradation of methylene blue (MB) with the rate constant of 4.415 × 10−4 s−1 under solar simulated irradiation. The improved performance of these materials can be attributed to the effective photo-induced charge transfer and reduced recombination, which make these nanocomposite materials promising candidates for the development of high-performance next-generation photocatalyst materials. Further, scavenging experiments were carried out to confirm the reactive oxygen species (ROS) involved in the photocatalytic degradation. It can be observed that there was a 78% reduction in the rate of degradation when IPA was used as the scavenger, whereas around 95% reduction was attained while N2 was used as the scavenger. Notably, very low degradation (&lt, 5%) was attained when the dye alone was directly under solar irradiation. These results further validate that the •OH radical and the superoxide radicals can be acknowledged for the degradation mechanism of MB, and the enhancement of degradation efficiency may be due to the combined effect of in situ dye sensitization during the catalysis and the impregnation of low bandgap materials on TiO2.

The worldwide increase in generation of solar based electricity prompts the essentiality of research efforts on the development of energy storage systems. In this regard, self-powered photocapacitors are of keen interest as they can directly convert and store the solar energy in the form of electrical energy in a single device. This study reports the photoelectrochemical energy storage capacity of a novel photocapacitor fabricated with FTO/Activated Carbon (AC)/Ag2CrO4/SnS nanostructured photoanode. Initially, the Ag2CrO4 and SnS nanostructures were synthesized using simple ultrasonication technique and hydrothermal method, respectively. The crystallinity, morphology and optical properties of the synthesized nanostructures were then studied. The XRD patterns indicated orthorhombic structure of both Ag2CrO4 and SnS. Their optical band gaps were calculated as 1.93 and 1.65 eV, respectively using Kubelka-Munk plots. The FTO/AC/Ag2CrO4/SnS photoanode was then fabricated and photoelectrochemical studies, namely cyclic voltammetry and electrochemical impedance spectroscopy were carried out on a three electrode system. The FTO/AC/Ag2CrO4/SnS photoanode showed a specific capacitance of 4782 mF/g at the scan rate of 10 mVs−1 when the device was subjected to visible light illumination (1 sun). Hence, the fabricated heterostructured photoanode provides a promising path for the design and synthesis of novel highly efficient solar energy harvesting and storage materials as photocapacitors.

In this study, P25-titanium dioxide (TiO2) was doped with ruthenium (Ru) by systematically varying the Ru content at 0.15, 0.30, 0.45 and 0.6 mol%. The synthesized Ru-doped TiO2 nanomaterials have been characterized by X-ray diffraction (XRD), Raman spectroscopy, energy-dispersive X-ray (EDX) analysis, UV-visible (UV−Vis) spectroscopy, and electrochemical impedance (EIS) spectroscopy. The XRD patterns of undoped and Ru-doped TiO2 nanomaterials confirm the presence of mixed anatase and rutile phases of TiO2 while EDX spectrum confirms the presence of Ti, O and Ru. Further, UV-visible absorption spectra of doped TiO2 nanomaterial reveal a slight red shift on Ru-doping. The short circuit current density (JSC) of the cells fabricated using the Ru-doped TiO2 photoanode was found to be dependent on the amount of Ru present in TiO2. Optimized cells with 0.3 mol% Ru-doped TiO2 electrodes showed efficiency which is 20% more than the efficiency of the control cell (η = 5.8%) under stimulated illumination (100 mWcm−2, 1 sun) with AM 1.5 filter. The increase in JSC resulted from the reduced rate of recombination upon doping of Ru and this was confirmed by EIS analysis.

This study focuses on incorporating multi-walled carbon nanotubes (MWNT) in nanoporous titanium dioxides (TiO2) thin film for enhancing the performance of hybrid poly(3-hexylthiophene)(P3HT)/TiO2 solar cells. MWNTs were successfully incorporated in the nanoporous TiO2 electrodes either by systematically blending or dipping prior to the deposition of P3HT. Current density–voltage (J-V) characteristic of the corresponding fabricated devices showed that the short-circuit current density (JSC) and fill factor are strongly influenced by the amount of MWNT incorporated into TiO2 nanoparticles. Solar cells with optimum amount of MWNT incorporated by blending in nanoporous TiO2 layer showed a factor of two efficiency enhancement, mainly due to improvement in JSC compared to the corresponding control device. Further increment in MWNT reduces the efficiency mainly due to a sharp drop in fill factor and VOC, which can be attributed to shunting by excess amount of MWNTs. Devices with MWNT dip-coated TiO2 and polymer too showed enhanced efficiency over 2.5% under AM 1.5 illumination (100 mW cm−2), which is a factor of three higher than the corresponding control device.

This study focuses, synthesising and characterising Ni/N co-doped P25–TiO2 nanostructure electrodes for photovoltaic application. The X-ray diffraction (XRD) patterns confirm the presence of major anatase and minor rutile phases of TiO2 for un-doped, doped and co-doped nanoparticles. The UV–Visible spectra of un-doped, Ni-doped, N-doped and Ni/N co-doped nanoparticles reveal gradual red shift in light absorption and reduction in TiO2 bandgap. Enhanced light absorption observed for dye-coated Ni/N co-doped TiO2 electrode relative to the doped and un-doped electrode may be attributed to the increased surface area for dye adsorption/dye loading capacity due to synergistic effect of Ni and N doping. The improved surface roughness of Ni/N co-doped TiO2 electrode, confirmed by AFM, leads to high dye adsorption. The photovoltaic performance of the fabricated DSSCs was examined under simulated irradiation intensity of 100 mWcm−2 with AM 1.5 filter. The Ni/N co-doped device exhibited 35% higher than that of the control device (un-doped TiO2 based DSSC). The improvement in the PCE of the co-doped device is predominantly due to the increase in short circuit current density (JSC) as a result of higher light absorption ability and reduced charge transport resistance of the co-doped electrode.

Research and development activities on sodium-ion batteries are becoming prominent in the past few years. Compared to lithium-based batteries, the sodium-based batteries will be cheaper because of the abundancy of sodium raw materials in the earth’s crust and also in seawater. In the current study, we synthesized and characterized poly-acrylonitrile (PAN)-based gel-polymer electrolytes formed with NaClO4 and dissolved in ethylene carbonate (EC) and propylene carbonate (PC). By systematically varying the weight ratios of polymer, salt, and the solvents, we obtained an optimum room temperature ionic conductivity of 4.5 mS cm−1 for the composition 11PAN-12NaClO4-40EC-37PC (wt.%), which is reasonably good for practical applications. This value of conductivity is comparable to a few other Na+ ion conducting gel-polymer electrolyte systems studied in the recent past. Variation of ionic conductivity with inverse temperature showed Arrhenius behavior. Activation energies estimated for all the samples showed only a slight variation suggesting that a single activation process which depends on the EC/PC co-solvent governs the ionic mobility in these gel-polymer electrolytes. Thermo-gravimetric analysis (TGA) revealed that there is no noticeable weight loss of these electrolytes up to 100 °C and hence the electrolytes are thermally stable for operating temperatures up to 100 °C.

This study focuses on the influence of interface modifiers on the charge transport of hybrid nanoporous titanium dioxide (TiO2)/poly(3-hexylthiophene) (P3HT) nanocomposites by using the time of flight technique. We found that the hole-mobility in the nanocomposites is about three orders of magnitude less than that of pristine P3HT. This may be due to poor infiltration of the polymer into the highly structured porous TiO2 which in turn obstructs the charge transport of the carriers. However, the hole-mobility in the nanocomposites is increased by an order of magnitude when a ruthenium based dye, either Z907 or N719, is introduced at the TiO2/P3HT interface. Surprisingly, the electron-mobility of the composite is decreased upon dye treatment. We further observed that the hole-mobility of nanocrystalline TiO2/P3HT composites treated with a 3-hexylthiophene derivative with a cyanoacrylic acid group [(E)-2-cyano-3-(3′,3′′,3′′′-trihexyl-[2,2′:5′,2′′:5′′,2′′′-quaterthiophene]-5-yl)acrylicacid] (4T) increased to over 10−5 cm2 V−1 s−1, which is over an order of magnitude higher than the hole-mobility found in untreated nanocomposites. This trend in hole-mobility is consistent with corresponding current density (J)–voltage (V) characteristics under illumination of TiO2/P3HT devices with or without a dye interface layer. The higher hole-mobility found in the 4T dye treated TiO2/P3HT nanocomposite is assigned to passivation of surface traps by the dye as well as improved packing of the polymer with the nanocrystals through effective inter-chain interactions of 4T with P3HT.

Transition metal chalcogenides have intensively focused on photocatalytic hydrogen production for a decade due to their stronger edge and the quantum confinement effect. This work mainly focuses on synthesis and hydrogen production efficiencies of cobalt disulfide (CoS2)-embedded TiO2 nanocomposites. Materials are synthesized by using a hydrothermal approach and the hydrogen production efficiencies of pristine CoS2, TiO2 nanoparticles and CoS2/TiO2 nanocomposites are compared under UV irradiation. A higher amount of hydrogen production (2.55 mmol g&minus, 1) is obtained with 10 wt.% CoS2/TiO2 nanocomposite than pristineTiO2 nanoparticles, whereas no hydrogen production was observed with pristine CoS2 nanoparticles. This result unveils that the metal dichalcogenide&ndash, CoS2 acts as an effective co-catalyst and nanocrystalline TiO2 serves as an active site by effectively separating the photogenerated electron&ndash, hole pair. This study lays down a new approach for developing transition metal dichalcogenide materials with significant bandgaps that can effectively harness solar energy for hydrogen production.

This study focuses on employing cuprous iodide (CuI) as a hole-transporting material (HTM) in fabricating highly efficient perovskite solar cells (PSCs). The PSCs were made in air with either CuI or 2,2&prime, 7,7&prime, Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9&prime, spirobifluorene (spiro-OMeTAD) as HTMs. A simple and novel pressing method was employed for incorporating CuI powder layer between perovskite layer and Pt top-contact to fabricate devices with CuI, while spiro-OMeTAD was spin-coated between perovskite layer and thermally evaporated Au top-contact to fabricate devices with spiro-OMeTAD. Under illuminations of 100 mW/cm2 with an air mass (AM) 1.5 filter in air, the average short-circuit current density (JSC) of the CuI devices was over 24 mA/cm2, which is marginally higher than that of spiro-OMeTAD devices. Higher JSC of the CuI devices can be attributed to high hole-mobility of CuI that minimizes the electron-hole recombination. However, the average power conversion efficiency (PCE) of the CuI devices were lower than that of spiro-OMeTAD devices due to slightly lower open-circuit voltage (VOC) and fill factor (FF). This is probably due to surface roughness of CuI powder. However, optimized devices with solvent-free powder pressed CuI as HTM show a promising efficiency of over 8.0 % under illuminations of 1 sun (100 mW/cm2) with an air mass 1.5 filter in air, which is the highest among the reported efficiency values for PSCs fabricated in an open environment with CuI as HTM.

In this work, chemical bath-deposited cadmium sulfide (CdS) thin films were employed as an alternative hole-blocking layer for inverted poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction solar cells. CdS films were deposited by chemical bath deposition and their thicknesses were successfully controlled by tailoring the deposition time. The influence of the CdS layer thickness on the performance of P3HT:PCBM solar cells was systematically studied. The short circuit current densities and power conversion efficiencies of P3HT:PCBM solar cells strongly increased until the thickness of the CdS layer was increased to ~70 nm. This was attributed to the suppression of the interfacial charge recombination by the CdS layer, which is consistent with the lower dark current found with the increased CdS layer thickness. A further increase of the CdS layer thickness resulted in a lower short circuit current density due to strong absorption of the CdS layer as evidenced by UV-Vis optical studies. Both the fill factor and open circuit voltage of the solar cells with a CdS layer thickness less than ~50 nm were comparatively lower, and this could be attributed to the effect of pin holes in the CdS film, which reduces the series resistance and increases the charge recombination. Under AM 1.5 illumination (100 mW/cm2) conditions, the optimized PCBM:P3HT solar cells with a chemical bath deposited a CdS layer of thickness 70 nm and showed 50% power conversion efficiency enhancement, in comparison with similar solar cells with optimized dense TiO2 of 50 nm thickness prepared by spray pyrolysis.

Self-assembled monolayers (SAMs) of benzoic acid based molecules are used to modify the metal oxide–polymer interface in a hybrid poly-3-hexylthiophene (P3HT)/TiO2 photovoltaic device structure. The effect of SAMs on current density is in accordance with expectation from the driving force for charge separation of metal oxide–polymer interface in a hybrid poly-3-hexylthiophene (P3HT)/TiO2 photovoltaic device. However, the effect of monolayers on open circuit voltage is quite unexpected from the interfacial energetics as all the monolayers improve the open circuit voltage in spite of different sign of the interfacial dipole for different SAMs. This suggests that the monolayers have additional functions. Overall device performance is enhanced by more than a factor of two using a SAM with permanent dipole pointing towards the TiO2 surface or pointing towards polymer when compared to a control device with no interface modifiers. This study concludes that the SAM layer has two functions that are to shift the position of the conduction band of the porous TiO2 relative to the polymer HOMO level so as to influence interfacial charge separation and to act as a barrier layer, insulating back electron transfer from the TiO2 to the polymer. Both effects can benefit the performance of hybrid polymer metal oxide solar cells.

This study focuses on incorporating single wall carbon nanotubes (CNTs) in both electron conducting porous Titanium dioxide (TiO2) and the hole conducting Poly(3-hexylthiophene) (P3HT) layers in order to enhance the performance of perovskite solar cells. The CNT was incorporated at TiO2/CH3NH3PbIxCl3-x interface by dip coating TiO2 electrodes with CNT solution prior to deposition of CH3NH3PbIxCl3-x and by blending with P3HT, respectively. Raman spectra and Atomic Force Microscopic (AFM) images confirmed the presence of CNT in TiO2 electrodes and in P3HT, respectively. Optimized devices with the CNT show overall power conversion efficiencies (PCE) over 14%, under 100 mW/cm2 illumination with Air Mass 1.5 filter, which is 50% higher than that of the control device which is not having CNT. The enhancement is predominantly due to increase in short circuit current density (JSC) and fill factor, which resulted from surface passivation at the interface by CNT.

This work reports the influence of a Ru based dye (RuC) on enhancing the performance of nanocrystalline titanium dioxide (TiO2)/Poly(3-hexylthiophene) (P3HT) solar cells. UV–Vis absorption spectra of TiO2/P3HT and TiO2/RuC/P3HT films reveal that the absorption spectrum of TiO2/P3HT is broadened in the UV region due to the addition of the RuC dye. With pumping laser at the wavelength corresponds to maximum absorption of P3HT, photoluminescence (PL) of TiO2/RuC/P3HT nanocomposite film was significantly quenched in comparison with PL of TiO2/P3HT film which confirms the efficient exciton dissociation in TiO2/RuC/P3HT. The insertion of the dye suppresses the dark current by two orders of magnitude in the cells while extends external quantum efficiency (EQE) spectra and hence increases the average short circuit current density (JSC) from 2.52 (±0.25) to 6.44 (±0.43) mA/cm−2, resulting in three fold power conversion efficiency (PCE) increment from 0.73 (±0.06) to 2.35 (±0.13) %, under 100 mW cm−1 (1 sun) illumination with AM 1.5 filter.

This work focused on studying the effect of cadmium sulfide (CdS) interfacial layer on the performance of titanium dioxide (TiO2)/poly (3-hexylthiophene) (P3HT) solar cells and finding out its effect on charge recombination dynamics of hybrid TiO2/P3HT solar cells. FESEM images confirm the uniform distribution of chemical bath deposited CdS layer on TiO2 nanoparticles. Insertion of CdS layer at the nanocrystalline TiO2/P3HT interface broadens quantum efficiency spectrum of the solar cells with peak values over 80 and 40 % at the wavelengths of maximum absorption of CdS and P3HT respectively and hence enhances short-circuit current density (JSC) from 3.5 to 5.9 mAcm−2 under simulated illumination (70 mWcm−2) with an AM 1.5 filter. CdS layer further improves open circuit voltage (VOC) from 0.35 to 0.57 V, which is consistent with higher built-in voltage in CdS/P3HT than in TiO2/P3HT due to relatively lower laying conduction band edge of CdS. Photovoltaic transient measurements show that the carrier life-time in TiO2/CdS/P3HT solar cell is an order of magnitude longer than that in TiO2/P3HT solar cell. Optimized TiO2/P3HT solar cells with CdS interlayer yield power conversion efficiencies over 1.5 %, which is three times greater than that for similar solar cells without CdS layer.

This study focuses on enhancing the charge transport in hybrid TiO 2 P3HT solar cells by incorporating Multi Wall Carbon Nanotube (MWCNT) within the nanoporous TiO2 electron transporting layer. We systematically changed the weight ratio of MWCNTs which was blended with TiO2 nanoparticles and studied the effect caused in hole-mobility using Time of Flight technique. We found two orders of magnitude increase in hole-mobility while adding 0.02wt % MWCNT into porous TiO2. This is consistent with the corresponding current-voltage characteristics of above solar cells.

This work focused on studying the influence of dyes, including a thiophene derivative dye with a cyanoacrylic acid group ((E)-2-cyano-3-(3&prime, 3&prime, &prime, trihexyl-[2,2&prime, 5&prime, 2&prime, quaterthiophene]-5-yl) acrylicacid)(4T), on the photovoltaic performance of titanium dioxide (TiO2)/poly(3-hexyl thiophene)(P3HT) solar cells. The insertion of dye at the interface improved the efficiency regardless of the dye used. However, 4T dye significantly improved the efficiency by a factor of three when compared to the corresponding control. This improvement is mainly due to an increase in short circuit current density (JSC), which is consistent with higher hole-mobility reported in TiO2/P3HT nanocomposite with 4T dye. Optical absorption data further revealed that 4T extended the spectral response of the TiO2/P3HT nanocomposite, which could also enhance the JSC. The reduced dark current upon dye insertion ensured the carrier recombination was controlled at the interface. This, in turn, increased the open circuit voltage. An optimized hybrid TiO2/P3HT device with 4T dye as an interface modifier showed an average efficiency of over 2% under-simulated irradiation of 100 mWcm&minus, 2 (1 sun) with an Air Mass 1.5 filter.

Hybrid nanocrystalline titanium dioxide (TiO2)/polymer solar cells draw intense interest due to the potential advantages of nanocrystalline TiO2. The poly(styrenesulfonate)-doped poly(ethylenedioxy thiophene) (PEDOT:PSS) layer spin-coated below the top electrode in these solar cells had shown enhanced performance in previous studies, which motivated to explore the dependence of the thickness of the PEDOT:PSS layer on its performance. This study focused on the characterization of solar cells fabricated with poly(3-hexylthiophene) (P3HT) polymer with a silver electrode and different PEDOT:PSS layer thicknesses, in the dark and under AM 1.5 stimulated illumination with the intensity varying from 10 to 100 mW/cm 2 . The variations in the photovoltaic parameters, particularly the open-circuit voltage, proved that the PEDOT:PSS layer significantly affects the photovoltaic parameters through the characteristic changes in the morphology as well as the electrical properties. Discussed herein is the possible influence wielded by the thickness of the PEDOT:PSS layer on different factors, such as the series and shunt resistances, the mode of recombination, the reduction of the energy barrier, and the diffusion of silver. The optimum power conversion efficiency was observed for the as-prepared devices with 50-nm-thick PEDOT layers. The optimum power conversion efficiency, however, shifted to that corresponding to the 80 nm thick PEDOT:PSS layer about 30 weeks after the fabrication. A sublinear variation of the short-circuit current density with the intensity was found in the aged cells with relatively lower PEDOT:PSS layer thicknesses, supporting the view of dominant recombination contributed from bimolecular recombination in the cells with lower PEDOT:PSS thicknesses. The significantly increased open-circuit voltage and the more stable current density in the aged devices are the main causes of the improved performance of the cells generally with above 60 nm thick PEDOT:PSS layers. These, along with the long-term stability found in the cells with reasonably thick PEDOT:PSS layers, may be a figure of merit, most probably attributable to the comparatively minimized diffusion of silver nanoparticles.

In this work, alternative architecture for polymer/fullerene solar cells has been explored using titanium dioxide nanolayers which invert the polarity of the cell and may relax the necessity to have a hole-collecting buffer layer poly(styrene sulfonate)-doped poly(ethylene dioxy-thiophene) (PEDOT:PSS). This work particularly focuses on the performance of the inverted devices with dense TiO 2 nanolayers as a function of temperature, illumination intensity and time. We find that both temperature and illumination intensity slightly influence the power conversion efficiency of devices with the PEDOT:PSS layer. However, the inverted solar cells without the PEDOT:PSS layer showed very different characteristics regarding the power conversion efficiency which increased significantly with the operating temperature from 30 °C to 65 °C. This was attributed to a consequence from the strong and positive temperature dependence of open-circuit voltage which may be due to a "kink" in the current―voltage characteristics near the open-circuit voltage.

This study focuses on influence of interface modifiers on hole mobility in Hybrid Nanoporous Titanium dioxide (TiO2) / Poly(3-hexylthiophene) (P3HT) nanocomposite by using time of flight technique. We found that the hole-mobility in the composite material is more than two orders of magnitude less than that of pristine P3HT. This may be due to poor polymer infiltration of the polymer into highly structured porous TiO2. However, hole-mobility of the polymer in TiO2/P3HT is increased to an order of magnitude when ruthenium based dye either Z907 or N719 is introduced at the TiO2/P3HT interface. This is consistent with corresponding current density (J) - voltage (V) charateristics of thin TiO2 / P3HT devices with or without dye interface layer. Better JV characteristics of the device and higher hole mobility of P3HT found in TiO2 / dye / P3HT may be due to passivation of surface traps by the dye.

We report a study of the effects of polymer optoelectronic properties on the performance of photovoltaic devices consisting of nanocrystalline TiO2 and a conjugated polymer. Three different poly(2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylenevinylene) (MEH-PPV)-based polymers and a fluorene–bithiophene copolymer are compared. We use photoluminescence quenching, time-of-flight mobility measurements, and optical spectroscopy to characterize the exciton-transport, charge-transport, and light-harvesting properties, respectively, of the polymers, and correlate these material properties with photovoltaic-device performance. We find that photocurrent is primarily limited by the photogeneration rate and by the quality of the interfaces, rather than by hole transport in the polymer. We have also studied the photovoltaic performance of these TiO2/polymer devices as a function of the fabrication route and device design. Including a dip-coating step before spin-coating the polymer leads to excellent polymer penetration into highly structured TiO2 networks, as was confirmed through transient optical measurements of the photoinduced charge-transfer yield and recombination kinetics. Device performance is further improved for all material combinations studied, by introducing a layer of poly(ethylene dioxythiophene) (PEDOT) doped with poly(styrene sulfonic acid) (PSS) under the top contact. Optimized devices incorporating the additional dip-coated and PEDOT:PSS layers produced a short-circuit current density of about 1 mA cm–2, a fill factor of 0.50, and an open-circuit voltage of 0.86 V under simulated AM 1.5 illumination (100 mW cm–2, 1 sun). The corresponding power conversion efficiency under 1 sun was ≥ 0.4 %.

Composites of nanostructured metal oxides with conjugated polymers are promising material combinations for efficient solar energy conversion. However, performance of such combinations is normally limited by the low interfacial area of planar structures and poor charge carrier mobility of the polymer. In this study, we focus on TiO 2 with a high hole-mobility polymer, poly (9,9′-dioctylfluorene-co-bithiophene) (F8T2). Transient optical spectroscopy confirms that efficient photo-induced electron transfer occurs from F8T2 to TiO 2 in both planar TiO 2 /F8T2 structures and in high surface area, porous TiO 2 /F8T2 structures. Recombination between the positive polaron in the polymer and electron in the TiO 2 is remarkably slow (∼ms) in both cases. The influence of layer thickness and surface morphology on cell performance was examined. The best cell was made with reduced layer thickness and increased surface morphology and offered an external quantum efficiency of 11.5% and monochromatic power efficiency of 1 at.% 440 nm. This cell produced an open circuit voltage V oc of 0.80 V and a short circuit current density of approximately 300 μA/cm 2 under simulated air mass (AM) 1.5 illumination. However, the power conversion efficiency is limited by a poor fill factor, which is attributed to an energy barrier at the polymer/metal interface. We investigate this problem using alternative polymer and top contact metals.

Porous titanium dioxide is an attractive material for solar cell application on account of its stability, electron transport properties, and the possibilities for controlling surface morphology as well as for its ease of fabrication and low cost. NanostructuredTiO2has been intensively studied for applications to dye sensitised solar cells. The performance of the titanium dioxide based solar cells is influenced, among other factors, by the electron mobility of the porous titanium dioxide. Different fabrication processes for porous titanium films result in different film morphology, which in turn affects the electron transport. We have employed three different techniques namely, electrostatic spray assisted vapour deposition (ESAVD), D.C. reactive sputtering, and doctor blading of sol-gel dispersions to deposit thinTiO2films onto indium tin oxide (ITO) coated glass substrates. All these films exhibited only the anatase phase as confirmed by X-ray diffraction analysis. Using the time-of-flight technique, the electron drift mobility in the porousTiO2films was measured. The results show that in the low field region (<55,000 Vcm−1) the mobility, in all the films, were in the range of10−7to10−6cm2Vs−1. The drift mobility in the films prepared by reactive sputtering was consistently higher than in the films prepared by the two other techniques. Sputter deposited films had lower porosity (∼10% and 36% for normal-, and oblique (60∘)-angle deposited films) compared to∼50% for films deposited by the two other techniques. The relationship between the drift mobility and film morphology is discussed with the aid of scanning electron microscopy studies.

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We report on a study of post-processing treatments in hybrid solar cells based on poly(3-hexylthiophene) (P3HT) being in contact with nanocrystalline TiO2 films. The power conversion efficiency of the hybrid polymer/TiO2 solar cells is increased over three-fold through the simultaneous application of external bias voltage and UV illumination. These treatments enhance short-circuit current density, J(SC), from 1 mA/cm(2) to over 3 mA/cm(2) under simulated air mass (AM) 1.5 conditions (100 mW cm(-2)) and lead to a peak external quantum efficiency of over 16%. The AM 1.5 open circuit voltage reaches 0.47 V and the fill factor reaches 0.53, resulting in an overall power conversion efficiency of 0.74%. The improved performance following UV exposure is correlated to a slowing of over one order of magnitude in the dynamics of charge recombination as monitored by transient optical spectroscopy. We further demonstrate that while the UV radiation present in a simulated AM 1.5 solar spectrum is sufficient to cause the increase in the J(SC) and efficiency after two hours of exposure, no change results from exposure to the same spectrum when a UV blocking filter is used. We propose that UV exposure modifies the nature or density of surface trapping species in the nanocrystalline TiO2, resulting in reduced recombination rates and a higher efficiency of collection of photogenerated charges., The authors thank Prof. James Durrant, Department of Chemistry, Imperial College London, for permitting them to take transient absorption spectroscopic measurements in his laboratory. PR and JN thank the Royal Society for financial support of PR's academic visit to Imperial College London. We also thank the EPSRC Excitonic Supergen Programme (EP/G031088) and the EPSRC Materials for Energy Programme (EP/E036341/1) for financial support. PA acknowledges the support of the Spanish Ministry of Science for a post-doctoral fellowship.