Successive Ionic Layer Adsorption And Reaction Cycles Research Articles

A comparative analysis of solid-state quantum dot-sensitized solar cells employing various hole transport layers, metal contacts, and a sensitizer comprising PbS/CdS/ZnS quantum dots

Quantum dots, as a sensitizer in quantum dot-sensitized solar cells (QDSSCs), hold the promise of revolutionizing solar energy conversion. This research mainly focuses on employing PbS/CdS/ZnS quantum dots (QDs) as both light harvesters and passivation layers in QDSSCs, which are directly synthesized onto the pre-deposited TiO2 substrate through the Successive Ionic Layer Adsorption and Reaction (SILAR) technique. Particularly, the sample with a composition of 2 cycles of PbS, 6 cycles of CdS, and 2 cycles of ZnS (2/6/2) exhibited a wide-ranging and intense absorption spectrum, attributed to the reduction in band gap with escalation in number of SILAR cycles. The prepared samples underwent analysis through characterization methods, including SEM and XRD, and the elemental composition was examined using EDX spectroscopy. Subsequently, the 2/6/2 sample was employed as a sensitizer, with P3HT and PEDOT:PSS serving as the hole transport layers (HTL). For the metal contacts, thermally evaporated gold (Au), silver (Ag), and Ag paste were used in the fabrication of six distinct devices. FTO/TiO2/PbS/CdS/ZnS/P3HT/Au shows the best performance demonstrating PCE of 2.17 %, Jsc of 7.9 mA/cm2 Voc of 0.54 V and FF of 0.51. However, overall efficiency dropped significantly for other configurations. Additionally, impedance spectroscopic analysis revealed a notably low series resistance for the P3HT/Au configuration.

Highly Efficient CdSe Quantum Dot-Sensitized Solar Cells via a Facile SILAR Method: Dependence of the SILAR Cycles on Optical Properties and Photovoltaic Performance

This work emphasizes using CdSe as a sensitizer in quantum dot-sensitized solar cells (QDSSCs) due to its beneficial band alignment with TiO2, enhancing effective charge injection. This study presents highly efficient CdSe QDSSCs developed using the successive ionic layer adsorption and reaction (SILAR) method. The XRD analysis revealed a hexagonal crystal structure for the synthesized CdSe quantum dots (QDs) with an average particle size of 9.2 nm. Increasing the SILAR cycles from 3 to 5 showed a decrease in the energy bandgap, reducing it from 1.79 eV to 1.68 eV, as observed in the investigation of optical properties. The optimal photovoltaic performance of CdSe QDSSCs was achieved at 4 SILAR cycles, yielding a notable power conversion efficiency (PCE) of 6.77% (Jsc = 14.63 mA/cm2, Voc = 0.71 V, FF = 65.2%), which is higher than that of a previous report of SILAR-prepared CdSe QDSSCs.

Effect of SILAR cycle on gas sensing properties of In2O3 thin films for CO gas sensor

In2O3 thin films were deposited via Successive Ionic Layer Adsorption and Reaction (SILAR) method on glass substrates at 20, 30, 40, and 50 SILAR cycles. The effect of SILAR cycle on the general and CO gas sensing properties of the films was investigated. The GIXRD and FE-SEM results indicated that the films had cubic phase and porous morphology. As a function of temperature and gas concentration, CO gas sensing measurements of In2O3 thin film-based sensors were made, and the detection limit and operating temperature values were determined. The optimal operating temperature was found to be 222 °C for all sensors. The CO sensing results demonstrated that the sensor with 30 SILAR cycle had higher sensitivity for 1–100-ppm gas concentration values at 222 °C operating temperature than the others. The sensing responses of the sensors increased from 12 to 29% for 1-ppm CO gas and from 52 to 91% for 100-ppm CO gas at 222 °C, depending on the SILAR cycle. The detection limit of the sensors toward CO gas at 222 °C reached 1 ppm, and the response and recovery times of the sensor with 30 SILAR cycle were found to be 54.2 s and 49 s for 1-ppm CO, and 47.4 and 62.5 s for 100-ppm CO gas at 222 °C, respectively. The activation energy (Ea) values of the sensors were found to change between 0.08 and 0.15 eV in the temperature range of 300–340 K and between 0.700 and 0.749 eV in the temperature range of 350–520 K, with SILAR cycle number. Finally, in this study, it was revealed that SILAR cycle number changed the structural, morphological, and CO gas sensing properties of the In2O3 thin films, and SILAR cycle optimization was performed for the highly sensitive In2O3 thin film-based CO gas sensor.

Utilization of glycerol solution for hydrogen production by a combination of photocatalysis and electrolysis processes with Fe-TiO2 nanotubes

A combination of photocatalysis and electrolysis (photoelectrocatalysis) for the simultaneous degradation of glycerol and hydrogen production using Fe-TiO2 nanotubes has been studied. This photocatalyst was synthesized through Ti anodization followed by Fe deposition with Fe(NO3)3 as precursor using the SILAR (successive ionic layer adsorption and reaction) method. The effects of Fe loading (based on the number of SILAR cycles) on TiO2 nanotubes and glycerol concentration were examined. The generated TiO2 nanotubes were 100% anatase phase with crystallite size between 25 and 29 nm. The results of UV-Vis DRS showed that the number of SILAR cycles of Fe dopant determined the magnitude of the decrease in the band gap of photocatalysts up to 2.74 eV, notably lower than a typical value of 3.15 eV associated with TiO2 anatase. FESEM/EDX, TEM, and HRTEM characterizations indicated the formation of neatly arranged TiO2 nanotubes with Fe deposited on the surface. The photoelectrocatalytic process increased the hydrogen produced by up to 5 times compared to a single photocatalytic or electrolysis process. The photocatalyst sample with Fe deposited on TiO2 nanotubes via a SILAR method with 15 cycles outperformed its bare TiO2 nanotube counterpart by producing hydrogen by 2.5 times (405.8 mmol/m2). Glycerol photo-reforming at 10% concentration produced hydrogen 6 times greater than water splitting (0% glycerol).

Bi2S3 nanoparticles anchored MWCNTs towards core-shell architecture: Counter electrode for dye-sensitized solar cell

A core-shell surface architecture has been developed through cost-effective and efficient sequential growth controlled chemical route, namely; successive ionic layer adsorption and reaction (SILAR) method to anchor Bi2S3 nanoparticles as shell over pre-coated MWCNTs as core to serve as a counter electrode (CE) in dye-sensitized solar cells (DSSCs) with eosin-Y dye loaded ZnO as photoanode, and polyiodide as liquid electrolyte. Electrochemical and device performance studies have been used to yield optimum growth through the number of SILAR cycles of Bi2S3 over MWCNTs. Electrochemical impedance spectroscopy (EIS) analysis revealed that, for well-optimized MWCNTs/Bi2S3 core-shell based device, the synergistic effect at the CE/electrolyte interface not only results in lower charge transfer resistance and faster electron transfer from CE to the electrolyte but equally doubled efficiency (0.343 %) than bare MWCNTs (0.162 %) and eight-fold enhanced efficiency than bare Bi2S3 (0.040 %).

Photovoltaic ZnO/SnSx heterostructures obtained by “electrochemical deposition-successive ionic layer adsorption and reaction” approach

In this work, ZnO/SnS/indium tin oxide (ITO)/glass functional heterostructures have been developed using a combined approach of electrodeposition of a SnSx layer and successive ionic layer adsorption and reaction (SILAR) of the ZnO layer. The high-quality 400 nm-thick orthorhombic SnS0.9–0.95 films were formed on the ITO substrates with a thickness of 130 nm and an electrical conductivity of less than 40 Ω/□. Chemical deposition of ZnO thin films by the SILAR method allowed to deposit hexagonal films with a thickness of about 200 nm. The morphology, elemental and phase composition of the films were characterized by Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The band gap (1.4 eV for SnSx and 3.3 eV for ZnO), as well as the high light absorption coefficient of SnSx films (1–2) × 104 cm–1 were determined. The obtained ZnO/SnSx/ITO heterostructures formed by the electrodeposition–SILAR cycle showed a photoEMF value of 198 mV. These properties make ZnO/SnS heterostructure promising for low-cost solar cells based on affordable materials.

Bi2Ti2O7/PbCdS2/PbS solar cells with NiS@rGO Electrocatalyst: A strategy for enhancing light absorption and polysulfide reduction

The pyrochlore structure of bismuth titanate (Bi2Ti2O7) has been used as a photo-anode to fabricate PbCdS2 sensitized solar cells. The ternary PbCdS2 alloy has been coated with the thin Bi2Ti2O7 (BTO) films by optimizing the successive ionic layer adsorption and reaction (SILAR) cycles. The structure and chemical composition have been identified through X-ray diffraction and X-ray photoelectron spectral analysis. The nanorods-like morphology has been observed from the morphological analysis. J-V results demonstrate that the BTO/3PbCdS2 with NiS counter electrode (CE) cell has a better power conversion efficiency (PCE) of 1.03 % with a JSC of 4.56 mA cm−2, VOC of 49 mV, and FF of 0.39, which is superior to other BTO/PbCdS2 combinations and pristine CdS and PbS. Furthermore, the PCE is increased by sandwiching the NiS-rGO CE with the BTO/3PbCdS2/Sn2-/S2- and attaining a maximum JSC of 5.65 mA cm−2, VOC of 539 mV, FF of 0.56, and PCE of 2 %. The obtained FF and are 43 % and 94 % higher than the BTO/3PbCdS2/Sn2-/S2-/NiS cell, respectively. The improvement is owing to increased light absorption, perhaps due to a favorable band position, lower carrier recombination, and the effective polysulfide reduction of NiS-rGO. The results suggest that optimized SILAR cycles are not the only approach to attaining a superior PCE; implanting an effective electrocatalyst is also a viable option.

Bi2Se3 nanoparticles anchored MWCNTs: Counter electrode in a dye-sensitized solar cell

Anchoring of Bi2Se3 nanoparticles over ‘dip and dry’ coated multiwalled carbon nanotubes (MWCNTs) has been accomplished using a room-temperature (27 °C), inexpensive, and convenient chemical route, namely, successive ionic layer adsorption and reaction (SILAR), to yield a nanohybrid composite electrode to serve as a counter electrode (CE) in dye-sensitized solar cell (DSSC) applications. The growth of Bi2Se3 on MWCNTs has been well-tuned through varying SILAR cycles (MBSe-series) and tested as counter electrodes (CEs) with reference to MWCNTs and Bi2Se3 in FTO/ZnO/Eosin-Y/Iodide-triiodide/Counter electrode/FTO assembly. Grown CEs have been validated through XRD, XPS, Raman, FTIR, and FESEM studies, while the assembled DSSCs have been assessed through JV, EQE, EIS, and electrochemical stability studies. Well-optimized Bi2Se3/MWCNTs nanohybrid composites have been used as CEs in DSSCs and showed superior device performance (0.52 %) compared to bare MWCNTs (0.14 %) and Bi2Se3 (0.09 %) due to the well-anchored Bi2Se3 over one-dimensional MWCNTs through a large number of synergistic electrochemical active sites. A DSSC fabricated with MBSe-12 as the CE exhibits enhanced stability compared to bare Bi2Se3 and MWCNTs. Also, it reveals a charge transfer resistance of 7.92 Ω/cm2 and an electron lifetime of 16 μs, yielding a maximum efficiency of 0.52 % and an external quantum efficiency of 28.20 %.

Enhancement in absorption spectrum by ITO coated, down converting glass and increasing the SILAR cycles of PbS/CdS quantum dots sensitized ZnO nano with deposition of MoO3/Au/MoO3 (MAM) as a solid state solar cell

This research describes the first-of-its-kind quantum dots sensitized solar cell (DC/ITO/ZnO/PbS/CdS/MoO3/Au/MoO3) that is efficient and economical. A down-converting (DC) transparent glass was prepared. One side of DC glass was coated with indium tin oxide (ITO) by sputter-coating technique to make it conductive for electric current. Zinc oxide (ZnO) nanorods were produced by the several steps of hydrothermal process. The PbS/CdS quantum dots (QDs) were then grown on top of ZnO nanorods by using a process known as Successive Ionic Layer Adsorption and Reaction (SILAR). The final layer for the back contact was deposited as a trilayer of (MoO3/Au/MoO3).Spin coating was employed in the process of depositing MoO3 layers, while thermal evaporation was used in the process of depositing the intermediate layer of gold (Au). For the deposition of (CdS/PbS) quantum dots with different number of SILAR cycles (10, 15 and 20) were employed. Afterwards MoO3/Au/MoO3 trilayer was deposited on the quantum dots (CdS/PbS) attached with the nanorods ZnO for the complete fabrication of three devices. As compared to the other quantum dots sensitized solar cell (QDSSC), it can absorb light from both ends which produced the remarkable results. Surface morphology, elemental and structural analyses were employed by SEM, EDS and XRD methods. UV–Visible analysis was performed to identify the optical properties of the devices. Overall performances were calculated of the three different devices by their power conversion efficiencies. The highest efficiency among all three devices was 10% corresponding to the 15 SILAR cycles.

Effect of MgO recombination barrier layer on the performance of monolithic-structured solid-state dye sensitized solar cells

ABSTRACT In this paper, the optical, structural and electrical properties of pure and magnesium-doped TiO2 nanoparticles (NPs) of different cycles (2, 4, 6 and 8 cycles) were explored systematically. The magnesium-doped TiO2 was synthesised through successive ionic layer adsorption and reaction (SILAR) and deployed into dye sensitised solar cells. The effects of the MgO barrier layer was evaluated . The results show enhanced optical properties with MgO coating with a diminished band gap energy. The X-ray diffraction studies show that the anatase phase was preserved after doping and the dopant does not change the crystalline phase of the TiO2. The SEM results show well-dispersed morphology. For the device with 4 SILAR cycles of MgO, gains in open-circuit voltage, current density and simultaneous increase in efficiency were observed which is attributed to improved charge collection efficiency as electrons diffusing through TiO2 have a better chance of reaching the electrode before recombining. At greater SILAR cycles (6 and 8), losses in photocurrent caused net decrease in efficiencies. The results presented in this report implies that the modification of TiO2 with a metal oxide (MgO) can result to good photon management.

A novel SiO2–ZnS-Am-TiO2/PbS–CdS@ZnO-NRs/FTO photoanode based quantum dots sensitized solar cell

In this study, a novel and cost-effective design of a solar cell was introduced that utilized array of Zinc Oxide (ZnO) nanorods sensitized with Lead Sulfide (PbS) and Cadmium Sulfide (CdS) quantum dots (QDs). Three devices of the proposed solar cell architecture were fabricated using Fluorine-doped Tin Oxide (FTO) coated glass as a substrate and varying numbers of successive ionic layer adsorption and reaction (SILAR) cycles (10, 15, and 20) for PbS/CdS QDs sensitization. Three additional layers (Amorphous TiO2, ZnS, SiO2) were added to prevent charge recombination and ensure efficient charge transfer. The ZnO nanorods were formed and confirmed by scanning electron microscopy (SEM) analysis, which revealed that the relatively dense packing density of nanorods provided an adequate surface area for attachment of the PbS/CdS QDs. The optical properties of the solar cells were studied using UV–Visible spectroscopy, which showed that the optical absorption increased with an increase in the number of SILAR cycles. The proposed solar cell architecture exhibited a remarkable power conversion efficiency of 5.12%, which was attributed to the synergistic effects of the ZnO nanorods and PbS/CdS QDs. The unique design of solar cells with additional passivation layers makes it highly efficient, cost-effective, and easy to fabricate. Moreover, the use of readily available materials and the simplicity of the fabrication process make it a promising candidate for large-scale photovoltaic applications. Maximum efficiency of 5.12% was obtained. The finding of this study confirms that the proposed novel architecture can be a promising solar cell.

Experimental study on photocatalytic CO2 reduction performance of ZnS/CdS-TiO2 nanotube array thin films

Abstract The effect of CdS/ZnS composite-sensitized TiO2 nanotube array (TNTA) on the photocatalytic reduction of CO2 was studied. CdS/ZnS quantum dots sensitized TNTA by successive ionic layer adsorption and reaction (SILAR) cycle method, and CdS/ZnS-TNTA composite semiconductor materials were prepared. The loading amount of CdS/ZnS depends on the number of SILAR cycles. The effects of SILAR cycle times, the CO2 volume flow, and light intensity on the photocatalytic CO2 reduction performance were studied. The main product of the photocatalytic reduction of CO2 was methanol; the performance was 2.73 times higher than that of bare TNTA, the optimal SILAR cycle was 10, the light absorption sideband was red shifted to 524 nm, and the optimal CO2 volume flow rate was 20.5 mL/min. The final yield was as high as 255.49 nmol/(cm2-cat h). CdS/ZnS quantum dot sensitization mainly broadened the wavelength range of the catalyst’s response to visible light, inhibited the recombination of electron–hole pairs to a certain extent, and greatly improved the photocatalytic performance under visible light.

PbS Quantum Dots-Decorated BiVO4 Photoanodes for Highly Efficient Photoelectrochemical Hydrogen Production.

While metal oxides such as TiO2, Fe2O3, WO3, and BiVO4 have been previously studied for their potential as photoanodes in photoelectrochemical (PEC) hydrogen production, their relatively wide band-gap limits their photocurrent, making them unsuitable for the efficient utilization of incident visible light. To overcome this limitation, we propose a new approach for highly efficient PEC hydrogen production based on a novel photoanode composed of BiVO4/PbS quantum dots (QDs). Crystallized monoclinic BiVO4 films were prepared via a typical electrodeposition process, followed by the deposition of PbS QDs using a successive ionic layer adsorption and reaction (SILAR) method to form a p-n heterojunction. This is the first time that narrow band-gap QDs were applied to sensitize a BiVO4 photoelectrode. The PbS QDs were uniformly coated on the surface of nanoporous BiVO4, and their optical band-gap was reduced by increasing the number of SILAR cycles. However, this did not affect the crystal structure and optical properties of the BiVO4. By decorating the surface of BiVO4 with PbS QDs, the photocurrent was increased from 2.92 to 4.88 mA/cm2 (at 1.23 VRHE) for PEC hydrogen production, resulting from the enhanced light-harvesting capability arising from the narrow band-gap of the PbS QDs. Moreover, the introduction of a ZnS overlayer on the BiVO4/PbS QDs further improved the photocurrent to 5.19 mA/cm2, attributed to the reduction in interfacial charge recombination.

Cadmium sulphide-sensitized zirconium dioxide (ZrO2) photoanode by successive ionic layer adsorption and reaction for solar cell application

In the present study, cadmium sulphide (CdS) quantum dot-sensitized ZrO2 photoanodes have been analysed by using the facial and cost-effective method, popularly known as successive ionic layer adsorption and reaction (SILAR), performed at 300 K. The presence of compact layer and ZnS treatment of the as-prepared photoanode is studied in this article to improve the solar cell parameters. The X-ray diffraction peaks infer the nano-crystalline nature of ZrO2 films with an average particle size of 39.14 nm. The CdS-sensitized ZrO2 films show a significant increase in absorption of photons in the visible region (i.e., 200 to 520 nm) of the absorption spectrum, as we have increased the number of SILAR cycles. Poly-sulphide electrolytes have been prepared in double distilled water and carbon black soot on conducting substrate is used as a counter electrode to be economical. The J–V characteristic of 10 CdS/ZrO2 with a compact layer of TiO2 with surface passivation (ZnS) treatment gives the maximum Jsc of 1.46 mA/cm2 with a fill factor of 0.34 and conversion efficiency of 0.46%. Electrochemical impedance spectroscopy of the quantum dot-sensitized solar cell is studied to understand the kinetics of charge transfer and transport processes mechanisms involved.

High-performance PbS/CdS quantum dot Co-sensitized hierarchical ZnO nanowall photoanodes decorated on electrochemically reduced graphene

In this study, we report the vertically aligned ZnO nanowalls (NWs) decorated electrochemically reduced graphene oxide (ERGO) structures co-deposited directly on the FTO substrates by a simple and one-pot electrochemical technique. Then, these ERGO/ZnONWs were co-sensitized with a successive layer of PbS and CdS quantum dots (QDs) by a successive ionic layer adsorption and reaction (SILAR) technique for the fabrication of ERGO/ZnONWs/PbS/CdS photoelectrodes. The effect of the number of PbS and CdS SILAR cycles on the photocurrent response of ERGO/ZnONWs photoelectrodes was systematically investigated by varying the SILAR cycle number. The QDSSCs were fabricated by using the PbS, CdS and PbS/CdS QDs decorated ERGO/ZnONWs as photoelectrode, copper (I) sulfide (Cu2S) as the counter electrode, and polysulfide redox couple (S2−/Sx2−) as an electrolyte. Compared with ERGO/ZnONWs photoelectrode sensitized with single QDs (PbS or CdS), the PbS/CdS co-sensitized ERGO/ZnONWs photoelectrodes showed the best performance with efficiency (η) of 5.85%, open-circuit voltage (Voc) of 0.65 V, a short circuit current density (Jsc) of 23.01 mA.cm−2, and a fill factor (FF) of 0.39 under one sun illumination, which is relatively higher than other PbS/CdS co-sensitized ZnO based QDSSCs previously reported in the literature. In this cascaded FTO-ERGO/ZnONWs/PbS/CdS, CdS serves as a passivating layer to PbS and contributes light absorption and highly efficient injection of electrons from CdS to PbS and then to ZnO due to its higher CB band. The present study also highlights the potential of this novel ERGO/ZnONWs/PbS/CdS photoanode. It introduces simple, green, and economical electrochemical techniques for researchers interested in fabricating ERGO/ZnONWs for various applications.

Synergistic effect of CuxOy-NPs/TiO2-NTs heterostructure on the photodegradation of amido black staining

TiO2 nanotube arrays have been extensively investigated for optoelectronic applications besides their excellent photocatalytic activity. The present work aims to study TiO2 nanotubes (NTs) fabricated with the anodization of Ti substrates. CuxOy nanoparticles (NPs) were deposited on TiO2 nanotubes (NTs) using the Successive ionic layer adsorption and reaction (SILAR) method. The obtained nanocomposite was used in the photocatalytic degradation of synthetic organic pollutants (amido black). Particular emphasis was focused on the effect of the morphological, optical, and structural properties of the CuxOy (i.e., the number of SILAR cycles) on the photocatalytic efficiency of the formed heterostructure. The morphological structural and optical properties were investigated by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction analysis (XRD), UV–vis spectroscopy, and photoluminescence (PL), respectively. The results show the formation of TiO2 anatase NTs decorated with CuO and Cu2O NPs. The density and size of the Cu2O NPs were found to increase with the number of SILAR cycles, whereas the energy band gap is narrowed by 0.7 eV. Photocatalytic tests demonstrate that at 15 SILAR cycles, the Cu2O.CuO-NPs/TiO2-NTs heterostructure exhibits the highest photocatalytic performance, reaching 94 % of amido black degradation under UV irradiation (256 nm) for 90 min. The experimental data modeling indicates that the faster the degradation, the better the photocatalytic performance; i.e., the reaction rate k = 0.025 min-1. The current study highlights the potential of CuxOy decorated TiO2 substrates as efficient photocatalytic systems for degrading hazardous organic pollutants.

Developing a Z-scheme Ag2CO3/ZIF-8 heterojunction for the surface decoration of cotton fabric toward repeatable photocatalytic dye degradation

This paper presents a novel strategy for fabricating efficient, tailorable, and reusable photocatalytic cotton fabrics (CF) using the successive ionic layer adsorption and reaction (SILAR) method with Ag2CO3-doped zeolitic imidazolate framework-8 (ZIF-8) to degrade residual dyes from the textile industry. The Z-scheme photocatalytic degradation mechanism of ZIF-8/Ag2CO3/CF is also proposed. The results reveal that ZIF-8/Ag2CO3/CF prepared via 10 SILAR cycles photocatalytically degraded 91 % rhodamine B in 30 min. ZIF-8/Ag2CO3/CF had 15-fold higher photocatalytic activity than ZIF-8/CF. This enhancement was due to various effects, including, 1) the scattering of ZIF-8/Ag2CO3 nanoparticles on the fiber surface rather than inducing agglomeration using the SILAR method, 2) the prevention of Ag2CO3 photocorrosion by ZIF-8, and 3) the suppression of the recombination of photogenerated electrons and holes. Moreover, ZIF-8/Ag2CO3/CF maintained 85 % photocatalytic degradation efficiency after five cycles, indicating its high reusability potential. Overall, this research offers a facile process for fabricating efficient, stable, and reusable photocatalytic fabrics to tackle the wastewater treatment issue in the textile industry.

Co-sensitising cadmium selenide and cadmium telluride quantum dots on titanium dioxide nanorods via the SILAR method

Co-sensitised CdSe/ CdTe quantum dots (QDs) on the surface of TiO2 nanorods were fabricated via different cycles of successive ionic layer adsorption and reaction (SILAR) method. The deposition of the QDs onto TiO2 nanorods were confirmed with transmission electron microscopy. A higher number of SILAR cycles has led to QDs aggregation and overgrowth on the top layer of the TiO2 nanorods layer. Furthermore, the higher number SILAR cycles also lowered the charge transfer resistance as observed in the electrochemical impedance spectroscopy analysis. Based on the observation, 5 cycles were selected to be the optimized number of SILAR cycle. The sequential deposition of CdTe QDs increased the absorption intensity and extended the absorption spectra, demonstrating co-sensitisation effects, which increase the short circuit current density from 0.103 mA cm−2 to 0.158 mA cm−2 is shown to enhance the CdSe quantum dots sensitised solar cells (QDSSC) efficiency from 0.009 % to 0.018 %.

Photo-electrochemical performance of Cu2ZnSnS4 thin films prepared via successive ionic layer adsorption and reaction method

In this report, we have prepared the Cu2ZnSnS4 (CZTS) thin films by a simple and cost effective successive ionic layer adsorption and reaction (SILAR) technique. The layer by layer deposition of CZTS thin films were carried out by SILAR method. The number of SILAR cycles and the sequence of the binary chalcogenides was optimized to get better photo-electrochemical (PEC) performance of CZTS thin films. Meanwhile, the different physico-chemical characterization tools such as XRD, Raman were used to identify the phase and purity of the synthesized samples. The XRD and Raman studies confirmed the phase purity of the CZTS thin film deposited with Cu2S as underneath and ZnS as topmost or bottom layer. The surface morphological study reveals the uniform, compact microstructure of as prepared CZTS thin films. Meanwhile, the chemical composition and microstructures of material plays vital role in photovoltaic performance, including photo-electrochemical (PEC) conversion. In our report, we found uniform CZTS microstructure without any secondary phases; which utilize the visible light illumination to generate the electrical signals via chemical reactions with European nitrate as a redox mediator.

Optimizing the size and amount of CdS quantum dots for efficiency enhancement in CdS/N719 co-sensitized solar cells

Co-sensitization of TiO 2 photoanodes in solar cells with Ruthenium dye and quantum dots offer better photovoltaic performance compared to the sensitization by the dye only. In the present study, TiO 2 nanostructured photoanode was co-sensitized with CdS quantum dots and N719 dye. CdS quantum dots were deposited using successive ionic layer adsorption and reaction (SILAR). A suitable thin ZnS interfacial layer has been introduced between two sensitizers to prevent the corrosion of CdS quantum dots by the iodide-based liquid electrolyte. In order to get the highest efficiency, the number of SILAR cycles for CdS quantum dot deposition has been optimized. A power conversion efficiency of 6.79% with short-circuit current density of 15.55 mA cm −2 and open circuit voltage of 764.5 mV have been obtained for the co-sensitized solar cell made with TiO 2 /CdS/ZnS/N719 co-sensitized photoanode under the illumination of 100 mW cm −2 with AM 1.5 spectral filter. Efficiency and short-circuit current density of the solar cell have been enhanced by 11.31% and 6.58% respectively due to the co-sensitization. The optimized co-sensitized solar cell shows a higher incident photon to current conversion efficiency and a reduced electron recombination compared to the solar cell with dye-sensitized photoanode. Higher recombination resistance and longer electron lifetime of the solar cell with CdS/ZnS/N719 co-sensitized TiO 2 photoanode have contributed to the increased short circuit current and open circuit voltage leading to the enhanced efficiency of 6.79% which is among the highest for a co-sensitized dye sensitized solar cell . • TiO 2 photoanode was co-sensitized with CdS quantum dots and N719 dye. • ZnS layer was introduced between CdS and N719 to prevent the corrosion of CdS. • Number of CdS SILAR cycles was optimized to get the highest solar cell efficiency. • Solar cell efficiency of 6.79% was obtained for TiO 2 /CdS/ZnS/N719 photoanode. • New photoanode showed a high recombination resistance and long electron lifetime. • 6.79% is among the highest efficiencies reported for co-sensitized solar cells.