Enhanced electron harvesting in next generation solar cells by employing TiO2 nanoparticles prepared through hydrolysis catalytic process

Titanium dioxide (TiO₂) nanoparticles (NPs) were synthesized through solvothermal route by changing the rate of hydrolysis in the catalytic process. In order to change the hydrolysis rate, the concentration of acetic acid, as additive, was varied as 2 M, 3 M and 4 M. The synthesized NPs were examined by various physico-chemical characterization techniques. The powder X-ray diffraction (PXRD) analysis of the NPs reveals only the anatase phase of TiO_2. The spherical shaped morphology of the NPs was observed in the high-resolution transmission electron microscopy (HR-TEM) analysis. The optical behaviour such as absorption, bandgap, diffuse reflectance and photoluminescence (PL) emission of the NPs were studied. The material's nature and behaviors were scrutinized and they were employed as photoanode in dye sensitized solar cell (DSSC) and as electron transport layer (ETL) in carbon-based perovskite solar cell (C-PSC). The charge transfer at the interface of the devices was studied with electrochemical impedance spectroscopy (EIS). The fabricated DSSC and C-PSC show highest power conversion efficiency (PCE) of 6.1% and 10.6%, respectively. The highest current collection was detected in C-PSC and the results are discussed in detail.     

Plasmonic Effects of Infiltrated Silver Nanoparticles Inside TiO2 Film: Enhanced Photovoltaic Performance in DSSCs

The plasmonic effects of infiltrated silver (Ag) nanoparticles, with different contents, inside a nanostructured TiO₂ film on the photovoltaic performance of dye‐sensitized solar cells (DSSCs) are explored. The synthesized Ag nanoparticles are immobilized onto deposited TiO₂ nanoparticles by a new strategy using 3‐mercaptopropionic acid (MPA), a bifunctional linker molecule. Transmission electron microscope (TEM) images show that monodispersed Ag and polydispersed TiO₂ nanoparticles have an average diameter of 12 ± 3 nm and 5 ± 1 nm, respectively. Moreover, Fourier transform infrared spectroscopy (FTIR) analysis reveals that Ag nanoparticles were successfully functionalized and capped with MPA. Optical studies on the MPA‐capped Ag nanoparticles inside TiO₂ film show an increase in the total absorbance of the electrode. Moreover, EIS measurements confirm that MPA‐capped Ag nanoparticles inhibit the charge recombination and improve the stability of nanoparticles in I₃^?/I^? electrolyte. The DSSC assembled with optimal content of MPA‐capped Ag nanoparticles demonstrated an enhanced power conversion efficiency (8.82% ± 0.07%) compared with the pure TiO₂ (7.30% ± 0.05%). The increase in cell efficiency was attributed to the enhanced dye light absorption in strength and spectral range due to the surface plasmon resonance of MPA‐capped Ag nanoparticles in the photoanode.     

Pulsed laser ablation in liquid synthesis of ZnO/TiO2 nanocomposite catalyst with enhanced photovoltaic and photocatalytic performance

In this work, we employed an impurity-free nanoparticle synthesis technique, known as pulsed laser ablation in liquid (PLAL), to integrate titanium dioxide nanoparticles (TiO₂ NPs) into zinc oxide nanorods (ZnO NRs) with varying relative proportions. The main objective of this integration was to enhance the charge carrier separation of photo-generated electron hole pairs during solar irradiation. For the synthesis process, an Nd:YAG laser at 532 nm wavelength was applied as an ablation source, along with deionized water as a solvent medium in which the precursor materials were dispersed prior to laser irradiation. The nanocomposites were characterized by X-ray diffraction (XRD), UV–vis absorption and in-situ Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FE-SEM). The synthesized nanocomposites were primarily utilised in two applications: firstly, as a catalyst in the degradation of methyl orange (MO) and secondly, as photo-anode in dye sensitized solar cell (DSSC). Our research has demonstrated that optimal performance was obtained for the nanocomposite containing 10% and 90% (by weight) TiO₂ NPs and ZnO respectively, which we define as the ideal nanocomposite. Relative to pure ZnO, the photo-conversion efficiency of the ideal composite was improved substantially by 63.73%, whilst the photo-degradation rate was enhanced by 3 fold. The oxidation state and the microstructural of the segregated ideal nanocomposite confirms that oxygen vacancy defects were created when perfect surface integration occurs between TiO₂ and ZnO. Nonetheless, we believe that the performance enhancement is predominantly due to the excellent charge carrier separation and fast interfacial electron flow in this nanocomposite.     

Preparation of polyaniline/TiO2 nanocomposite film with good adhesion behavior for dye‐sensitized solar cell application

In this study, novel Polyaniline (PAni)/TiO₂ nanocomposites were applied on fluoride‐doped tin oxide (FTO) glass to act as an efficient counter electrode in dye‐sensitized solar cell (DSSC) application. PAni/TiO₂ nanocomposites were synthesized via chemical oxidation process using di‐2‐ethylhexylsulfosuccinate sodium salt (NaDEHS) as dopant. The nanocomposites were characterized using fourier transform infrared and ultraviolet‐visible spectrometers. In the application of PAni as the counter electrode in the solar cell, the film showed poor adhesion on the FTO glass. Palm oil‐based alkyd was introduced into the nanocomposite mixture to improve the adhesion of the film. The findings in the work show that strong adhesion of PAni on FTO glasses has led to higher incident photon to current conversion efficiency (IPCE) in solar cell. The short circuit current (Jsc), Voc (open circuit voltage), and IPCE of the resulted PAni/TiO₂ counter electrode with good adhesion in DSSC are 15.8 mA/cm², 670 mV, and 3.0%, respectively. POLYM. COMPOS., 34:1884–1891, 2013. © 2013 Society of Plastics Engineers     

Effect of gold nanoparticles on the performances of TiO2 dye-sensitised solar cell

TiO₂ blended with Au nanoparticles (NP) was hydrothermally synthesised under controlled conditions and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The dye-sensitised solar cells (DSSC) were characterized using the UV–vis spectrometry and current-voltage (I-V) testing. The performance of TiO₂-Au DSSC is significantly higher than TiO₂ DSSC. The addition of Au NPs improves the light harvesting efficiency of the DSSC, thus improving the short circuit current density, J_sc, and the conversion efficiency of the DSSC. The excitation of localised surface plasmon resonance of the Au nanoparticles utilised the strong local field enhancement around the Au NPs to increase the absorption in the surrounding TiO₂ layer. It was demonstrated that the power conversion efficiency of the DSSC was improved by 28% with the addition of Au NPs.     

The photovoltaic efficiencies on dye sensitized solar cells assembled with nanoporous carbon/TiO2 composites

This study examined the characterization of nanoporous structured carbon/TiO₂ composites and its application to dye-sensitized solar cells. TEM of nanoporous structured carbon revealed nanopore sizes of 2.0–3.0 nm with a regular hexagonal form. When nanoporous structured carbon was mixed to TiO₂ particles and then was applied to DSSC, the energy conversion efficiency was enhanced considerably compared with that using only nanometer sized pure TiO₂: the energy conversion efficiency of the DSSC prepared from nanoporous carbon/TiO₂ composites was approximately 3.38%, compared to 2.49% using pure TiO₂. We confirmed from FT-IR spectroscopy that the dye molecules were attached perfectly to the surface and more was absorbed on the nanoporous structured carbon/TiO₂ composite than on the pure TiO₂ particles. In impedance measurements, R₃ which means the Nernstian diffusion within the electrolytes was largely decreased in a cell assembled by nanoporous carbon/TiO₂ composites than that of TiO₂.     

Aminosilicate modified zinc oxide Nanorod-GO nanocomposite for DSSC photoanodes

Amine-functionalized ZnO nanorods@graphene oxide (ZnO-NR/NH₂/GO) nanocomposites prepared by a facile solution route have been investigated through X-ray diffraction, diffuse reflectance spectra, Raman spectra, scanning electron microscopy and transmission electron microscopy. The amine-functionalized ZnO-NR/NH₂/GO-2 nanocomposite exhibits very strong visible light absorption. Dye-sensitized solar cell (DSSC) made of ZnO-NR/NH₂/GO-2 nanocomposite (with optimum 2 wt % GO) photoanode delivers a power conversion efficiency (PCE) of 3.76% which is much higher than the efficiency of unmodified ZnO-NR/GO photoanodes based DSSC (2.27%). The enhancement of PCE is primarily caused by the increased current density, attributed to the incorporation of aminosilicate and GO on the surface of ZnO-NRs which facilitates rapid transfer of electron from conduction band of ZnO to conducting surface of FTO. This diminished recombination of photogenerated electrons and holes improve the electron transfer at the photoanode/electrolyte interfaces.     

Double‐Layer Structure Photoanode with TiO2 Nanotubes and Nanoparticles for Dye‐Sensitized Solar Cells

Here, we report a novel double‐layer structure photoanode with TiO₂ nanotube (TNT) layer and TiO₂ nanoparticle (TP) layer via a two‐step method of electrochemical anodization and screen printing for dye‐sensitized solar cells (DSSCs). The results indicate that DSSCs with this double‐layer structure have significant advantages of large surface area, long electron lifetime, superior electron recombination restraint characteristics, and high light scattering. The layer thickness of nanotubes and nanoparticles is also investigated and finally an optimized double‐layer structure with excellent performance is prepared. With such a double‐layer structure photoanode, DSSC with a relative high conversion efficiency of 6.43% and a short‐circuit photocurrent density of 16.40 mA·cm^?2 is obtained.     

Synthesis and characterisation of thin-film TiO2 dye-sensitised solar cell

A TiO₂ dye-sensitised solar cell (DSSC) is fabricated and characterised using: X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), electron diffraction X-ray (EDX) analysis, UV–vis spectrometry and a current?voltage (I?V) test. Thicker anatase TiO₂ gives rise to better crystallinity and subsequently leads to better cell efficiency. Mesoporous TiO₂ with a suitable, average pore size results in higher conversion efficiency. Smaller particle sizes lead to higher dye uptake and increase short circuit current density, J_sc. Addition of scattering layer and/or dual TiCl₄ treatment for DSSCs having optimum thickness enhanced their performance. A DSSC having double TiO₂ layers (20 nm+50 nm) with dual TiCl₄ treatment achieved the highest conversion efficiency of 9.78%.     

Synthesis and Photocatalytic Activity of Anatase TiO2 Nanoparticles-coated Carbon Nanotubes

A simple and straightforward approach to prepare TiO₂-coated carbon nanotubes (CNTs) is presented. Anatase TiO₂ nanoparticles (NPs) with the average size ~8 nm were coated on CNTs from peroxo titanic acid (PTA) precursor even at low temperature of 100 °C. We demonstrate the effects of CNTs/TiO₂ molar ratio on the adsorption capability and photocatalytic efficiency under UV–visible irradiation. The samples showed not only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO) dye molecules. These properties facilitated the great enhancement of photocatalytic activity of TiO₂ NPs-coated CNTs photocatalysts. The TiO₂ NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO₂.     

Aqueous Colloidal Stability Evaluated by Zeta Potential Measurement and Resultant TiO2 for Superior Photovoltaic Performance

Controlling the morphological structure of titanium dioxide (TiO₂) is crucial for obtaining superior power conversion efficiency for dye‐sensitized solar cells. Although the sol–gel‐based process has been developed for this purpose, there has been limited success in resisting the aggregation of nanostructured TiO₂, which could act as an obstacle for mass production. Herein, we report a simple approach to improve the efficiency of dye‐sensitized solar cells (DSSC) by controlling the degree of aggregation and particle surface charge through zeta potential analysis. We found that different aqueous colloidal conditions, i.e., potential of hydrogen (pH), water/titanium alkoxide (titanium isopropoxide) ratio, and surface charge, obviously led to different particle sizes in the range of 10–500 nm. We have also shown that particles prepared under acidic conditions are more effective for DSSC application regarding the modification of surface charges to improve dye loading and electron injection rate properties. Power conversion efficiency of 6.54%, open‐circuit voltage of 0.73 V, short‐circuit current density of 15.32 mA/cm², and fill factor of 0.73 were obtained using anatase TiO₂ optimized to 10–20 nm in size, as well as by the use of a compact TiO₂ blocking layer.     

Fabrication of hole-patterned TiO2 photoelectrodes for solid-state dye-sensitized solar cells

We suggest a simple process to fabricate a hole-patterned TiO₂ electrode for a solid-state dye-sensitized solar cell (DSSC) to enhance cell performance through interfacial properties of the electrode with the electrolyte with minimum dye loading. The method involves prepatterning of SU-8 photoresist on a conducting glass, followed by the deposition of a nanocrystalline TiO₂ layer, calcination at 450 °C and characterization using scanning electron microscopy (SEM). Hole-patterned TiO₂ photoelectrodes yielded better solar energy conversion efficiency per dye loading compared to a conventional non-patterned photoelectrode. For example, a 50 μm hole-patterned DSSC exhibited 4.50% conversion efficiency in the solid state, which is comparable to an unpatterned flat TiO₂ photoelectrode (4.57%) however the efficiency per dye loading of the former (0.986%/g) was much greater than that of the latter (0.898%/g). The improvement was attributed to improved transmittance through the electrode as well as better interfacial properties between the electrolyte and electrode, as confirmed by UV-visible spectroscopy and electrochemical impedance (EIS) analysis.     

Synergetic effect of graphene sheet and three‐dimensional crumpled graphene on the performance of dye‐sensitized solar cells

Herein, an improved structure of the dye‐sensitized solar cell (DSSC) is demonstrated which is composed of surface modified fluorine‐doped tin oxide (FTO) glass with graphene (GR) sheets and TiO₂ films incorporated with three‐dimensional crumped graphene (3‐D CGR)/GR sheets. The morphologies of the as‐prepared GR sheets on FTO glasses and 3‐D CGR/GR sheets/TiO₂ films were observed by field‐emission scanning electron microscopy. Light harvesting and charge recombination kinetics were investigated with a solar simulator and electrochemical impedance spectroscopy analysis. In addition to the reduced charge resistance by the GR modified FTO, the enhanced dye loading capability of the 3‐D CGR, and the rapid charge transport by the 2‐D GR sheets, the power conversion efficiency was 7.2%, which was an increase of 56% compared to a “conventional” structured DSSC. © 2015 American Institute of Chemical Engineers AIChE J, 62: 574–579, 2016     

Dithizone,carminic acid and pyrocatechol violet dyes sensitized metal (Ho,Ba& Cd) doped TiO2/CdS nanocomposite as a photoanode in hybrid heterojunction solar cell

Considering the great importance of nanocomposite based photo-active nanomaterials for a variety of electronics, photonics and photovoltaics application, it is always worth considering to synthesize new hetreostructure. This paper describes the sol-gel and hydrothermal synthesis of metal (holmium, barium, and cadmium) doped TiO₂/CdS nanocomposites for photoanode applications. Various characterization techniques, including XRD, FTIR, UV–VIS, EDX, and SEM were used to examine the synthesized heterostructures. The band gap of pure TiO₂ NPs is 3.10 eV, which was effectively decreased to 2.16 eV by doping and coupling with CdS. The nanomaterial's crystallinity, crystallite size, morphology and elemental composition were determined by XRD, SEM and EDX, respectively. As sensitizers, the organic dyes dithizone, carminic acid, and pyrocatechol violet were used. FTIR was used to analyze the effective dye grafting on the surface of nanomaterials. In the presence of hole conducting P3HT polymer as solid state electrolyte, the sensitized materials were evaluated for solid state dye-sensitized solar cells. Compared to the reference device, Cd–TiO₂/CdS photosensitized using Pyrocatechol violet dye demonstrated the highest efficiency of 2.68% (0.82%). Other parameters of this device, including open circuit voltage (Voc) and short circuit current (Jsc), were determined to be 16.97 mA cm² and 0.41V, respectively.     

Improving the efficiency of dye-sensitized solar cell via tuning the Au plasmons inlaid TiO<Subscript>2</Subscript> nanotube array photoanode

Plasmonic enhancement is an effective method to improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). The size and amount of plasmon play key roles in plasmonic effect; however, the report on the relationship between morphology and processing of plasmon is rare. In this work, a series of Au nanoparticles (NPs) inlaid into TiO₂ nanotube (NT) based photoanodes have been synthesized through tuning HAuCl₄ solution concentration and irradiation time during the photoreduction process. Meanwhile, the optical and photoelectrical properties of these plasmonic DSSCs have also been verified. The results demonstrate that the optimized plasmonic DSSC (irradiation time: 5 min, solution concentration: 0.5 mM) showed a 19.0% improvement of PCE, compared to the reference DSSC without Au NPs. The improved PCE is mainly attributed to the enhanced photocurrent generated by surface plasmon resonance (SPR) effect of small sized Au NPs as well as light scattering effect of large sized particles.

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Effect of an electrodeposited TiO<Subscript>2</Subscript> blocking layer on efficiency improvement of dye-sensitized solar cell

A TiO₂ blocking layer in DSSC provides good adhesion between the fluorinated tin oxide (FTO) and an active TiO₂ layer, and represses the electron back transport between electrolyte and FTO by blocking direct contact. In addition, it offers a more uniform layer than bare FTO glass. In this study, a dense TiO₂ layer is prepared by electrodeposition technique onto an FTO substrate, and it is further used for efficiency measurement of dye-sensitized solar cell (DSSC). The thickness of TiO₂ blocking layers is controlled by applied voltage and deposition time. The morphology and crystalline structure of TiO₂ blocking layers are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The effect of thickness of TiO₂ blocking layers on transmittance is also examined by UV-vis spectrophotometer. For the best performance of the cell efficiency, the optimum blocking layer thickness is about 450 nm fabricated at 0.7 V for 20 min. The conversion efficiency from the DSSC including the optimum blocking layer is 59.34% improved compared to the reference cell from 2.41% to 3.84%. It demonstrates that the electrodeposition is a useful method to produce TiO₂ blocking layer for DSSC applications.     

Effect of silver (Ag) ions irradiation on the structural,optical and photovoltaic properties of Mn doped TiO2 thin films based dye sensitized solar cells

Dye sensitized solar cell (DSSC) is an emerging energy harvesting tool which converts direct sunlight into electrical energy. These cells have much better properties in contrast with silicon based solar cells because of their flexible nature, light weight, low cost, environment friendly nature, and involvement of a simple manufacturing process. Since, a photoanode is the backbone of DSSC, we synthesized a pure and 1% manganese (Mn) doped titanium dioxide (TiO₂) films by sol-gel method which are irradiated with silver (Ag) ions at two different concentrations (2 × 10¹⁴ and 4 × 10¹⁴) ions-cm^?2. X-ray diffraction revealed that Mn doping followed by Ag irradiation transformed TiO₂ from pure anatase to rutile phase. Ultraviolet–visible spectroscopy exposed the reduction in band gap of TiO₂ film during this doping and irradiation process. Therefore, absorption is enhanced with red shift in UV-range. When these films are used as a photoanode in DSSC, 1% Mn doped TiO₂ film exposed with Ag at the concentration of (2 × 10¹⁴) ions-cm^?2 exhibited maximum efficiency of 2.40%.     

Preparation of ZnO-coated TiO2 electrodes using dip coating and their applications in dye-sensitized solar cells

This study investigates the applicability of a ZnO-coated TiO₂ working electrode in a dye-sensitized solar cell (DSSC). This working electrode was designed and fabricated by the following procedures: (1) two consecutive TiCl₄ treatments were performed when preparing the TiO₂ electrode, one prior to and the other following the spin printing of the TiO₂ colloid on a FTO-glass (Fluorine doped tin oxide, SnO₂:F) substrate; (2) a simple dip coating method was used to fabricate a ZnO-coated TiO₂ electrode by immersing a FTO-glass substrate with a TiO₂ film in a solution of zinc acetate dehydrate [Zn(CH₃COO)₂?2H₂O] and ethanol. This working electrode was then immersed in a solution of N-719 (Ruthenium) dye at a temperature of 70 °C for a preset duration. Finally, the DSSC was assembled, and the short-circuit photocurrent, the open-circuit photovoltage, and the power conversion efficiency of DSSC were measured using an I–V measurement system. The effects of the concentration of Zn(CH₃COO)₂?2H₂O, the duration of dipping, and the dye loading on the power conversion efficiency of a DSSC were also examined. Most importantly, this study shows that the power conversion efficiency of the DSSC with a ZnO-coated TiO₂ electrode (6.62%) substantially exceeds that of the conventional DSSC with a TiO₂ electrode (5.45%) due to the effects of a ZnO barrier and the TiCl₄ treatment.     

Optimization of TiO2 paste concentration employed as electron transport layers in fully ambient air processed perovskite solar cells with a low-cost architecture

The optimization of thickness and surface roughness of the TiO₂ layer as an efficient electron transporting layer (ETL) plays a significant role on the performance improvement of perovskite solar cells (PSCs). In the present investigation, TiO₂ pastes synthesized with various concentrations under hydrothermal conditions were utilized to deposit the TiO₂ films of tunable porosities as the ETLs of PSCs. Also, the PSCs were fabricated with a structure of FTO/block-TiO₂ (b-TiO₂)/m-TiO₂/CH₃NH₃PbI₃ (MAPbI₃)/CuInS₂ (CIS)/carbon as a low-cost architecture. Moreover, the effect of the TiO₂ paste concentration was studied on the performances of PSCs under fully ambient conditions. The optimal TiO₂ layer was constructed with 20 wt% TiO₂ paste concentration, which resulted in the formation of a hole‐free, smooth, and compact ETL layer. The champion perovskite solar cell fabricated with the 20 wt% TiO₂ paste concentration showed the highest power conversion efficiency (PCE) of 13.09% (J_SC = 20.80 mA cm^?2, V_OC = 0.98 V and FF = 0.64) but the champion PSC device made with the 10 wt% TiO₂ paste exhibited the lowest PCE = 8.05% (J_SC = 19.83 mA cm^?2, V_OC = 0.91 V and FF = 0.45). These results illustrated that the optimal 20 wt% TiO₂ paste caused ～163% enhancement in the PCE of the device. Consequently, it could be suggested for application in fabrication of cost-effective and large scale PSCs.