Search

Reduced graphene oxide (rGO)-embedded WO3 composite thin film (rGO-WO3) is synthesized and investigated for its electrochromic performances. Furthermore, a novel application of quantum dot-sensitized solar cells (QDSSCs), to operate the rGO-WO3 electrochromic devices (ECDs), is demonstrated with development of an integrated device. The co-existence of both WO3 nanostructure and rGO sheet ameliorates the EC performances of composite thin film, compared to WO3 thin film. The rGO-WO3, possessing 0.1 g of rGO, nanocomposite shows an optimum optical contrast (%ΔT) of 66.3% and excellent optical stability displaying 1.7% degradation in %ΔT, while the WO3 film only exhibits a %ΔT of 52.2% and, 4.2% of optical degradation. Incorporation of rGO sheet into the WO3 nanostructure introduces de-agglomerated morphology, enhances electrochemically active surface area, and which facilitates the ion-transfer kinetics. The series-connected QDSSCs results an optimum open circuit voltage (Voc) of 1.03 V upon 1 sun illumination, which is found to be adequate for the study of switching performances of ECDs. QDSSCs assisted rGO-WO3 EC film exhibits a significant %ΔT of 43% and coloration time of 7 s. Additionally, QDSSCs device is illuminated with various light intensities to study the intensity and Voc dependent EC performances of rGO-WO3. [ABSTRACT FROM AUTHOR]

Today, nanoscrystals are researched and developed very quickly because of their advantages in many areas of life. One of the potential applications is quantum dot-sensitized solar cells. This is a green, clean, environmentally friendly cell, and has been studied by scientists since 2000. In this study, we fabricated photoanodes with Cu2+ ions co-doped into cadmium sulfide (CdS) and cadmium selenide (CdSe) nanoscrystals by successive ionic layer adsorption and reaction, and chemical bath deposition methods to improve absorption spectral intensity of films. The results showed that the absorption intensity increased by eight times compared with our previous results on Cu2+ ions doped with CdSe nanoscrystals. The CdS:Cu2+ film is optimized at 2% doping, the efficiency is 4.6819%, and the current density is 27.3501 mA.cm−2, which is higher when compared with the Cu2+ ion only doped into the CdSe quantum dot (19.915 mA.cm−2). In addition, the composition of the photoanode was determined by surface and cross-sectional field-emission scanning electron microscope images, and the structure of the film was determined by X-ray diffraction, energy-dispersive X-ray spectroscopy mapping and X-ray photoelectron spectroscopy. Finally, the film's optical properties were studied by ultraviolet-visible spectroscopy, photoluminescence spectroscopy and electrochemical properties by electrochemical impedance spectroscopy. The results obtained have been discussed and presented in great detail.

Third-generation solar cells, including dye-sensitized solar cells (DSSCs) and quantum dot-sensitized solar cells (QDSSCs), have been associated with low-cost material requirements, simple fabrication processes, and mechanical robustness. Hence, counter electrodes (CEs) are a critical component for the functionality of these solar cells. Although platinum (Pt)-based CEs have been dominant in CE fabrication, they are costly and have limited market availability. Therefore, it is important to find alternative materials to overcome these issues. Transition metal chalcogenides (TMCs) and transition metal dichalcogenides (TMDs) have demonstrated capabilities as a more cost-effective alternative to Pt materials. This advantage has been attributed to their strong electrocatalytic activity, excellent thermal stability, tunability of bandgap energies, and variable crystalline morphologies. In this study, a comprehensive review of the major components and working principles of the DSSC and QDSSC are presented. In developing CEs for DSSCs and QDSSCs, various TMS materials synthesized through several techniques are thoroughly reviewed. The performance efficiencies of DSSCs and QDSSCs resulting from TMS-based CEs are subjected to in-depth comparative analysis with Pt-based CEs. Thus, the power conversion efficiency (PCE), fill factor (FF), short circuit current density (Jsc) and open circuit voltage (Voc) are investigated. Based on this review, the PCEs for DSSCs and QDSSCs are found to range from 5.37 to 9.80% (I−/I3− redox couple electrolyte) and 1.62 to 6.70% (S−2/Sx− electrolyte). This review seeks to navigate the future direction of TMS-based CEs towards the performance efficiency improvement of DSSCs and QDSSCs in the most cost-effective and environmentally friendly manner. [ABSTRACT FROM AUTHOR]

Quantum dot-sensitized solar cells (QDSSC) have been regarded as one of the most promising candidates for effective utilization of solar energy, but its power conversion efficiency (PCE) is still far from meeting expectations. One of the most important bottlenecks is the limited collection efficiency of photogenerated electrons in the photoanodes. Herein, we design QDSSCs with a dual-photoanode architecture, and assemble the dual photoanodes with black TiO2 nanoparticles (NPs), which were processed by a femtosecond laser in the filamentation regime, and common CdS/CdSe QD sensitizers. A maximum PCE of 11.7% with a short circuit current density of 50.3 mA/cm2 is unambiguously achieved. We reveal both experimentally and theoretically that the enhanced PCE is mainly attributed to the improved light harvesting of black TiO2 due to the black TiO2 shells formed on white TiO2 NPs. [ABSTRACT FROM AUTHOR]

While the efficiency of quantum dot sensitized solar cells (QDSSCs) has been long limited by photogenerated electron extraction of photoanode, we propose here an alternative approach for boosting the light harvesting efficiency of QDSSCs, which is based on the modifications of the TiO2 photoanode absorbance and impedance by irradiating crystalline TiO2 nanoparticles with intense femtosecond laser pulses propagating in the filamentation regime. We demonstrate that a two-fold enhancement of the power conversion efficiency in CdSe/CdS-cosensitized solar cells is unambiguously achieved with the produced “black” TiO2 nanoparticles as photoanode, which allows for the light absorption in the spectral range of 240-2500 nm and enables possible facilitation of electron transport. Our results offer a viable route to boosting QDSSCs efficiency that is normally realized by optimizing the photoanode material morphology and structure as well as quantum dot species in QDSSCs.

Quantum dot-sensitized solar cells (QDSSC) have been regarded as one of the most promising candidates for effective utilization of solar energy, but its power conversion efficiency (PCE) is still far from meeting expectations. One of the most important bottlenecks is the limited collection efficiency of photogenerated electrons in the photoanodes. Herein, we design QDSSCs with a dual-photoanode architecture, and assemble the dual photoanodes with black TiO2 nanoparticles (NPs), which were processed by a femtosecond laser in the filamentation regime, and common CdS/CdSe QD sensitizers. A maximum PCE of 11.7% with a short circuit current density of 50.3 mA/cm2 is unambiguously achieved. We reveal both experimentally and theoretically that the enhanced PCE is mainly attributed to the improved light harvesting of black TiO2 due to the black TiO2 shells formed on white TiO2 NPs.

• Composite MXene/CoS based CE is first time used in QDSSCs. • The novel MXene/CoS CE shows better charge transfer and catalytic properties.. • The QDSSC with MXene/CoS CE exhibit a high efficiency of 8.09%. • A better photovoltaic performance than most of reported similar composite CEs. Low electrocatalytic activity and/or high charge transfer resistance of counter electrodes (CEs) in quantum-dot-sensitized solar cells (QDSSCs) are the main reasons for the low photovoltaic performance. Herein, the CoS nanoparticles are anchored on the MXene (Ti 3 C 2 T x) via a simple in-situ hydrothermal reaction process. It is the first attempt to use the MXene/CoS as a highly electrocatalytic CE for QDSSCs. The QDSSCs with a MXene/CoS CE shows a significant enhancement in cell performances and yields a promising power conversion efficiency (PCE) of 8.09% compared with that of the QDSSCs with bare CoS (5.77%) and bare MXene (4.25%) CEs. The significant enhancement of PCE value is mainly attributed to the synergistic effects of the unique layered morphology of conductive MXene nanosheets and its cocatalysis with CoS nanoparticles. The coupling of layered MXene with small CoS nanoparticles (~15 nm) provides abundant catalytic active sites. The improved mesoporous morphology contributes a high specific surface area and fast electron transfer channels for S x 2− reduction. Consequently, the MXene/CoS nanocomposite can be utilized as an effective agent to boost up the photovoltaic performance of QDSSCs. [ABSTRACT FROM AUTHOR]

In this prelimnary work, the aim was to fabricate a simple tin (II) sulfide (SnS) quantum dot-sensitized solar cell (QDSSC) from aqueous solution. The SnS QDSSCs were characterized by using current-voltage test (I-V test), scanning electron microscopy (SEM), and ultraviolet-visible (UV-Vis) spectroscopy. SEM results showed the presence of TiO2 and SnS elements in the sample, confirming the successful synthesis of SnS quantum dots (QDs). The overall efficiency of QDSSCs increased when concentration of the precursor solutions, which were aqueous sodium sulfide and tin (II) sulfate decreased from 0.5 M to 0.05 M. On the other hand, for a fixed precursor concentration, the efficiency of QDSSC reduced once an optimal cycle of of successive ionic layer adsorption and reaction (SILAR) was achieved. The bandgap energies of QDs obtained by extrapolating the Tauc plot were used to predict the QDs size. In general, the QD size was bigger for samples prepared from precursor concentration of 0.5 M, and with higher number of SILAR cycle used. The best performance was obtained from sample prepared from 0.05 M precursor concentration with 4 SILAR cycles.

[Display omitted] • The PCE of QDSSCs was improved by modifying polysulfide electrolytes. • The modified electrolytes were fabricated based on various additives. • The best-measured PCE was due to the presence of thiourea in the electrolyte. In this study, for the first time we reported a low-cost and straightforward method to modify the polysulfide electrolyte using amine additives including aromatic amines (1,8-naphthalenediamine, 1,5-naphthalenediamine), linear amines (ethylenediamine, diethylamine, ethylamine, tert -butylamine, and butylamine), thiourea, and urea in the polysulfide electrolyte system to improve the CdS/CdSe QDSSCs performance. The photovoltaic data showed that the highest power conversion efficiencies (PCEs) were obtained for 1,5-naphthalenediamine amongst aromatic amine groups, diethylamine amidst linear amine groups and thiourea. The best-measured PCE was 3.42% (J SC = 18.98 mA·cm−2, V OC = 0.50 V, FF = 0.36) at AM1.5, which was due to presence of thiourea additive in the polysulfide electrolyte. The results of data revealed that the interaction between thiourea additive, TiO 2 , and redox couple in the electrolyte solution caused to a molecular complex formation, increase the electron lifetime (τ), J SC and, ultimately, improve the PCE value compared to other additives under investigation in this study. [ABSTRACT FROM AUTHOR]

Pure ZnO nanorods and Y-doped ZnO nanorods (ZnO∶ Y) were prepared on conductive glass (FTO) substrate by two-step method. ZnO/CuInS2 and ZnO∶ Y/CuInS2 photoanodes were fabricated by successive ionic layer adsorption and reaction (SILAR), respectively. The crystal phase structure, micro-morphology, chemical composition, light absorption performance and solar cell efficiency of different photoanode samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer(EDS), ultraviolet visible spectrophotometer (UV-Vis) and current density-voltage (J-V) curves and other technical means. The experimental results show that the prepared ZnO nanorods and ZnO∶ Y nanorods have a hexagonal wurtzite structure. The optical band gap of the CuInS2 quantum dot-sensitized ZnO nanorod films reduce from 3. 22 eV to 2. 98 eV. Compared with ZnO CuInS2 photoanode solar cell, the short-circuit current density and photoelectric conversion efficiency of ZnO∶ Y/CuInS2 photoanodes solar cell increase by 6. 5% and 50. 4%, respectively. [ABSTRACT FROM AUTHOR]

Today, nanoscrystals are researched and developed very quickly because of their advantages in many areas of life. One of the potential applications is quantum dot-sensitized solar cells. This is a green, clean, environmentally friendly cell, and has been studied by scientists since 2000. In this study, we fabricated photoanodes with Cu 2+ ions co-doped into cadmium sulfide (CdS) and cadmium selenide (CdSe) nanoscrystals by successive ionic layer adsorption and reaction, and chemical bath deposition methods to improve absorption spectral intensity of films. The results showed that the absorption intensity increased by eight times compared with our previous results on Cu 2+ ions doped with CdSe nanoscrystals. The CdS:Cu 2+ film is optimized at 2% doping, the efficiency is 4.6819%, and the current density is 27.3501 mA.cm -2 , which is higher when compared with the Cu 2+ ion only doped into the CdSe quantum dot (19.915 mA.cm -2 ). In addition, the composition of the photoanode was determined by surface and cross-sectional field-emission scanning electron microscope images, and the structure of the film was determined by X-ray diffraction, energy-dispersive X-ray spectroscopy mapping and X-ray photoelectron spectroscopy. Finally, the film's optical properties were studied by ultraviolet-visible spectroscopy, photoluminescence spectroscopy and electrochemical properties by electrochemical impedance spectroscopy. The results obtained have been discussed and presented in great detail., Competing Interests: The authors declare that they have no known competing interests that could have appeared to influence the work reported to in this paper., (© 2024 The Authors.)

Highlights • The p-type CuS thin film exhibits high electrical conductivity. • CuS acts a hole transporting layer (HTL) facilitating smooth transfer of hole. • After introducing a HTL, the PCE improved by 55% with 0.6% PCE for TiO 2 /Bi 2 S 3 (4)/CuS. Abstract To search a viable way to enhance the photoconversion efficiency (PCE) of Quantum dot-sensitized solar cells (QDSSCs), we have designed a method of introducing a hole transporting layer (HTL) of p-type CuS to form the TiO 2 /Bi 2 S 3 /CuS composite electrodes. The morphology, crystal structure, optical properties and PEC performance of TiO 2 /Bi 2 S 3 /CuS composite electrodes were investigated in detail. The results showed that the photocurrent density of TiO 2 /Bi 2 S 3 /CuS was eight times higher than that of single TiO 2 and 1.51 times higher than that of TiO 2 /Bi 2 S 3 NRs. Therefore, this study provides helpful insights into rational design and fabrication of novel and efficient method for improving PEC performance of the QDSSCs. [ABSTRACT FROM AUTHOR]

Abstract In present work, Au nanoparticle-decorated TiO 2 nanorod array composite structure is designed and fabricated as the working electrode of CdS sensitized quantum dot-sensitized solar cells (QDSSCs). The results reveal that the intensity and range of sunlight absorption, photo-generated carriers transport efficiency and overall photoelectric conversion efficiency (PCE) were significantly enhanced due to followed reasons: Hot electrons of Au NPs excited by plasmon effect can offer extra electrons; plasmonic effect can contribute to the extraction and separation of light-generated electrons; the deposition of Au nanoparticles could effectively optimize the interface between TiO 2 nanorod and CdS QDs. As a result, an overall PCE of 3.29% has been obtained, which shows 19.6% enhancement compared with pure TiO 2 nanorod photoanode. Graphical abstract In present work, we developed a strategy to improve the performance of quantum dot-sensitized solar cells (QDSSCs) by using Au nanoparticle-decorated TiO 2 nanorod array as scaffold of photoanode. Image 1025 Highlights • A facile strategy was developed to prepare Au nanoparticle-decorated TiO 2 nanorod composite structure for efficient QDSSCs. • The Au nanoparticles are used to introduce plasmonic effect into photoanode. • Au nanoparticles are used to introduce plasmonic effect into photoanode. [ABSTRACT FROM AUTHOR]

Abstract A novel bidirectional (up and down)-conversion luminescence agent (GdBO 3 :Yb3+/Tb3+), that can convert ultraviolet lights and near-infrared lights into visible lights, is employed to enhance the light capture capability of CdSe 0.4 S 0.6 quantum dot-sensitized solar cells (QDSSCs). In this study, the GdBO 3 :Yb3+/Tb3+@TiO 2 photoanode is fabricated by sol-gel drop-coating method. And then, the CdSe 0.4 S 0.6 quantum dots (QDs) are deposited on the prepared photoanode surface by successive ionic layer adsorption and reaction (SILAR) technique at room temperature. The photoelectric measurements show that the light capture capability of the CdSe 0.4 S 0.6 QDSSCs device can be obviously enhanced after adding GdBO 3 :Yb3+/Tb3+ nanoparticles and the CdSe 0.4 S 0.6 /GdBO 3 :Yb3+/Tb3+@TiO 2 photoanode with 1.0% adding amount of GdBO 3 :Yb3+/Tb3+ displays the highest photovoltaic performance. The presence of GdBO 3 :Yb3+/Tb3+ nanoparticles makes CdSe 0.4 S 0.6 QDs indirectly utilize ultraviolet lights and near-infrared lights in solar lights. In addition, the scattering effect of GdBO 3 :Yb3+/Tb3+ nanoparticles in TiO 2 films can cause the reflection of the incident lights. The reflected lights can also be absorbed by the CdSe 0.4 S 0.6 QDs, increasing light capture capability. The research results demonstrate a potential applied value of bidirectional (up and down)-conversion luminescence agent in QDSSCs. Graphical abstract A novel bidirectional (up and down)-conversion luminescence agent (GdBO 3 :Yb3+/Tb3+), that can convert ultraviolet light and near-infrared light into visible light, is employed to improve the light capture capability of CdSe 0.4 S 0.6 quantum dot-sensitized solar cells (QDSSCs). The photoelectric measurements show that the light capture capability of the CdSe 0.4 S 0.6 QDSSCs devices can be obviously enhanced after adding GdBO 3 :Yb3+/Tb3+ nanoparticles and the CdSe 0.4 S 0.6 /GdBO 3 :Yb3+/Tb3+@TiO 2 photoanode with 1.0% adding amount of GdBO 3 :Yb3+/Tb3+ displays the highest photovoltaic performance. The presence of GdBO 3 :Yb3+/Tb3+ nanoparticles make CdSe 0.4 S 0.6 QDs indirectly utilize ultraviolet light and near-infrared light in solar light. In addition, the scattering effect of GdBO 3 :Yb3+/Tb3+ nanoparticles in TiO 2 films can cause the reflection of the incident light, which can be absorbed by the CdSe 0.4 S 0.6 QDs and also conduce to the increase of light capture capability. The research results demonstrate a potential of bidirectional (up and down)-conversion luminescence agent in QDSSCs. Image 1 Highlights • Bidirectional (up and down)-conversion luminescent agent is used in QDSSCs firstly. • GdBO 3 :Yb3+/Tb3+ can enhance the light capture capability of QDSSCs. • GdBO 3 :Yb3+/Tb3+ in photoanode have the function of scattering incident light. • Emitted light of GdBO 3 :Yb3+/Tb3+ locate in light absorption range of CdSe 0.4 S 0.6. [ABSTRACT FROM AUTHOR]

This work reports the synthesis and photovoltaic properties of a new semiconductor–ternary alloyed Ba x Cd 1 −x S nanocrystals, prepared by replacing a fraction of the Cd2+ ions in the host CdS with Ba2+ ions (x = 0−0.13) using the sequential ionic layer adsorption and reaction. Optical measurements revealed a decreasing bandgap in Ba x Cd 1 −x S from 2.24 to 2.14 eV with increasing x , increasing the optical absorption range from 300 to 553 nm in CdS to 300−579 nm in Ba x Cd 1 −x S. Liquid-junction semiconductor quantum dot-sensitized solar cells (QDSSCs) were fabricated from Ba x Cd 1 −x S nanocrystals using polysulfide electrolyte and CuS counter electrode. The Ba 0. 09 Cd 0. 91 S QDSSC (x = 0.09) yielded the best power conversion efficiency (PCE) of 3.95% under 1 sun, which is 33% higher than that (2.96%) of the host CdS. A ZnS passivation layer treatment on the best Ba 0.09 Cd 0.91 S sample increased the PCE to 4.57% (J SC = 9.33 mA/cm2, V oc = 0.80 V, fill factor = 61.2%) under one sun. The PCE further increased to 5.21% under a reduced light intensity of 0.1 sun. This work demonstrates the potential of tunable optoelectronic properties in Ba x Cd 1 −x S by controlling the Ba content and enhancing the photovoltaic performance by increasing the absorption range. [Display omitted] • The first demonstration of alkaline earth metal-doped Ba x Cd 1-x S quantum dot-sensitized solar cells. • The band gap decreases from 2.24 eV in CdS to 2.14 eV in Ba x Cd 1-x S. • The light absorption band increases from 300 to 553 nm in CdS to 300−579 nm in Ba x Cd 1−x S. • The PCE of Ba x Cd 1-x S QDSSCs is 33% higher than that of the host CdS cell. • The best PCE of Ba x Cd 1-x S QDSSCs equals 5.21% at 0.1 sun. [ABSTRACT FROM AUTHOR]

In this work, we report an electrodeposition technique for fabricating chalcopyrite phase CuInSe 2 (CISe) thin films and demonstrate the great prospect of CISe films for serving as efficient counter electrodes (CEs) in quantum dot sensitized solar cells (QDSCs). The as-prepared CISe materials, directly deposited onto conducting substrates, display long-range uniformity with high crystallinity and nanopillar shapes. A CISe CE-based CdS/CdSe QDSC delivers a considerable power conversion efficiency of 2.92%, coupled with excellent device stability. In contrast to the conventional noble Pt electrodes, CISe CEs exhibit much higher catalytic activity for electrocatalysing polysulfide electrolyte regeneration. This work offers a promising CE with superior catalytic capability for constructing highly efficient and stable QDSCs. [ABSTRACT FROM AUTHOR]

The electrochemical performance of counter electrodes (CEs) plays an important role for achieving high efficient quantum dot sensitized solar cells (QDSSCs). Considering the optical band gap energy of semiconductor materials and the V oc of the QDSSCs is determined by the energy difference between the quasi-Fermi levels ( q E f ) of the anode and cathode, so in this work, we synthesized the different metal sulfides and their composites including CuS/CoS, CuS/NiS, CuS, CoS and NiS by chemical bath deposition (CBD) method and used as CEs of QDSSCs. The effect of different CEs on performance of cells were investigated, and the best power conversion efficiency (η) of 5.22% was achieved by CuS/CoS CE, which is higher than that of CuS/NiS, CuS, CoS and NiS (η = 2.56%, 4.73%, 2.23% and 1.62%). The improved cell efficiency was attributed to the excellent electrical conductivity and catalytic activity of CuS and CoS, respectively. The result indicated t hat the combination of different metal sulfide composites could increase open-circuit voltage (V oc ) value without sacrificing the short-circuit current (J sc ), and leaving good perspectives for significantly higher solar cell performances. [ABSTRACT FROM AUTHOR]

Mesoporous nanoflakes Cu 2 S counter electrode (CE) was prepared from three-dimensional ordered macroporous (3-DOM) Cu film obtained by polystyrene microspheres assisted potentiostatic deposition for quantum dot-sensitized solar cell (QDSSC). The structrue of the Cu 2 S CE can be controlled by the size of polystyrene microspheres. The optimized Cu 2 S CE shows a charge transfer resistance (R CT ) as low as 1.24 Ω cm 2 , while the R CT of the Pt CE is 2250 Ω cm 2 . A CdSe QDSSC based on the mesoporous nanoflakes Cu 2 S CE achieved a power conversion efficiency of 6.01%, which was higher than that based on Pt CE (1.74%) and ordinary Cu 2 S CE (4.85%). This enhancement can be attributed to the increased surface area, the easy electrolyte diffution and the improved electron transport of mesoporous nanoflakes Cu 2 S CE. This work provides a new effective approach for the structure control of Cu 2 S CE for high-efficiency QDSSC. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS 2 ) films are electrochemically synthesized on F-doped SnO 2 (FTO) substrates using potentiostatic electrodeposition (ED) at a constant −1 V for 20–60 min. The MoS 2 is deposited according to island growth mode. As the ED time increases to 40 min, the clusters of MoS 2 nano particles enlarge and thicken, but maintain nanopores between the clusters. Additional increase in ED time (to 60 min) causes clusters to merge and make the film denser. Furthermore, this MoS 2 film exhibits cracks due to stress accumulated in the film. The film FTO/MoS 2 (40 min) shows significantly enhanced electrocatalytic activity compared to other films. This is because the FTO/MoS 2 (40 min) not only has more electrochemically active sites but also significantly facilitates charge transfer and mass transport. When it is employed as the counter electrode (CE) for quantum-dot and dye-sensitized solar cells (QD-SSC, D-SSC), the QD-SSC with FTO/MoS 2 (40 min) CE exhibits even higher overall energy conversion cell efficiency (3.69%) than that with Pt CE (2.16%). Moreover, the D-SSC with FTO/MoS 2 (40 min) CE exhibits cell efficiency (7.16%) similar to that with FTO/Pt CE (7.48%). This indicates that MoS 2 is a promising CE for all QD-SSCs and D-SSCs. [ABSTRACT FROM AUTHOR]

Polymer nano-composite composed of poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) and TiO 2 nano-particles was deposited on fluorine-doped tin oxide substrate and applied as an alternative to Au counter electrode of quantum dot-sensitized solar cell (QDSC). It became surface-richer with the increase in nano-particle amount so that catalytic reaction was increased by widened catalytic interface. Electrochemical impedance spectroscopy and cyclic voltammetry clearly demonstrated the enhancement of polymer nano-composite counter electrode. A QDSC based on polymer nano-composite counter electrode showed 0.56 V of V OC , 12.24 mA cm −2 of J SC , 0.57 of FF, and 3.87% of efficiency and this photovoltaic performance was higher than that of QDSC based on Au counter electrode (3.75%). [ABSTRACT FROM AUTHOR]

In the present work, {001}-faceted TiO 2 nanosheets were prepared via a one-step hydrothermal method and used as backbone scaffold of photoanodes of solar cells. The graphitic carbon nitride (g-C 3 N 4 ) was obtained by simple solid-state heat treatment and applied to modify the {001}-faceted TiO 2 nanosheet photoanodes. Compared with the photoanodes prepared from pure {001}-faceted TiO 2 nanosheets, the power conversion efficiency (PCE) of g-C 3 N 4 modified {001}-faceted TiO 2 nanosheet photoanodes was enhanced due to the suitable band-alignment between g-C 3 N 4 and TiO 2 . With 20% loading of g-C 3 N 4 in the photoanode, a maximum PCE of 4.23% with an open circuit voltage of 0.58 V, a short circuit current density of 15.5 mA/cm 2 , and a fill factor (FF) of 0.48 was achieved, giving 24.7% enhancement in the cell efficiency. Various characterizations were performed to understand the role of g-C 3 N 4 on the device performance, and the mechanisms that account for the improvement are suggested. [ABSTRACT FROM AUTHOR]

Herein, a TiO 2 nanoparticle/nanorod composite architecture was suggested for improving performance of quantum dot sensitized solar cells (QDSSCs), which was fabricated on transparent conductive glass substrates (FTO) via hydrothermal method followed by spin-coating, and further used as photoanode of QDSSCs. Compared with the TiO 2 nanorod photoanode, the power conversion efficiency (PCE) of the QDSSCs with this architecture was obviously improved. The champion efficiency of 4.42% was achieved, showing a 33.5% enhancement in PCE. The improved PCE mainly resulted from the increase of J sc , which increased from 9.80 (nanorod architecture) to 15.48 mA/cm 2 (nanoparticle/nanorod composite architecture). The advantages of the composite structure photoanode consist in the superior light scattering capability, faster electron transport and increased photogenerated electron concentration. [ABSTRACT FROM AUTHOR]

We report on the interfacial passivation mechanism in CdSe quantum dot-sensitized ZnO nanocrystalline thin film, where different sulfide semiconductors (such as ZnS and CdS) and sulfide ions are used to modify ZnO nanocrystalline thin film before deposition of CdSe quantum dots (QDs). It is noticed that the highest light-to-electric conversion efficiency of CdSe quantum dot-sensitized ZnO nanocrystalline thin film solar cell is attained up to 4.18 % after CdS interfacial modification. Meanwhile, a simple treatment of ZnO nanocrystalline thin film in NaS solution can also increase the conversion efficiency of CdSe quantum dot-sensitized solar cell up to 3.45 %. The electron transfer and recombination processes occurred in the interface of QD-sensitized nanocrystalline thin films with and without the different interfacial modifications are detected by measuring intensity modulated photovoltage spectroscopy and electrochemical impedance spectroscopy of solar cells. These results indicate that adsorption of S ions on the surface active sites of ZnO nanoparticles is the main reason for the conversion efficiency improvement due to the interfacial passivation of sulfide semiconductors. [ABSTRACT FROM AUTHOR]

Abstract Quantum dot-sensitized solar cells based on fluorine-doped tin oxide (FTO)/Au/TiO2/CdS photoanode and polysulfide electrolyte are fabricated. Au nanoparticles (NPs) as interfacial layer between FTO and TiO2 layer are dip-coated on FTO surface. The structure, morphology and impedance of the photoanodes and the photovoltaic performance of the cells are investigated. A power conversion efficiency of 1.62% has been obtained for FTO/Au/TiO2/CdS cell, which is about 88% higher than that for FTO/TiO2/CdS cell (0.86%). The easier transport of excited electron and the suppression of charge recombination in the photoanode due to the introduction of Au NP layer should be responsible for the performance enhancement of the cell.

[Display omitted] • Black rutile TiO 2 nanoparticles (NPs) is fabricated by fs laser filament processing. • CdS/CdSe quantum dot sensitized solar cells (QDSSCs) with black TiO 2 -NPs are assembled. • A power conversion efficiency of 9.1 % in QDSSCs is achieved. • The increase in PCE is ascribed to the formed amorphous shell on the surface of TiO 2 -NPs. The research deals with fabrication of CdS/CdSe-sensitized quantum dot sensitized solar cells (QDSSCs) with laser-engineered black rutile TiO 2 nanoparticles (TiO 2 -NPs) as the photoanode material. Three QDSSC devices with pristine and two types of black rutile TiO 2 -NPs engineered respectively in water and ethanol by intense femtosecond laser propagating in the filamentation regime were prepared in the same architecture. Extremely different power conversion efficiencies (PCE) of 1.43 %, 3.68 % and 9.11 %, in which the black TiO 2 -NPs-based devices show respectively a two-fold and six-fold PCE higher than the pristine TiO 2 -NPs, were obtained. The absorption and electrochemical impedance spectroscopy analyses revealed that the device with the highest PCE has the highest absorption efficiency in the wide spectral range from UV to mid-infrared and shunt resistance (R sh) of 1364.9 Ω, but the smallest series resistance (R s) of 190.3 Ω, which are attributed to the surface modification on the structural and optical properties of TiO 2 -NPs by femtosecond laser pulses. [ABSTRACT FROM AUTHOR]

TiO 2 nanoparticles are typically employed to construct the porous films for quantum dot-sensitized solar cells (QDSCs). However, undesirable interface charge recombination at grain boundaries would hinder the efficient electron transport to the conducting substrate, giving rise to the decline of open-circuit voltage ( V oc ). In this work, vertically aligned architectures of oriented one-dimensional (1D) TiO 2 nanorod arrays hydrothermally grown on substrates pave a way in designing highly efficient QDSCs with efficient radial-directional charge transport. SEM, TEM, XRD, and Raman spectroscopy were employed to characterize the as-prepared TiO 2 nanorods, showing the rutile phase with single-crystalline structure. The homogeneous deposition of CdS/CdSe QDs on the surface of TiO 2 nanorods has been achieved by in-situ grown strategies (i.e., successive ionic layer absorption and reaction, and chemical bath deposition). An extremely high V oc value up to 0.77 V has been achieved for CdS/CdSe QDSCs based on the well-ordered 1D nanorod arrays. To the best of our knowledge, it is the highest V oc reported for TiO 2 -based QDSCs. Dependencies of photovoltaic performance, optical absorption, and interfacial charge behavior on the length of nanorods were systematically investigated. A 1.7 μ m nanorod-array photoelectrode-based QDSC delivers a remarkable power conversion efficiency up to 3.57% under simulated AM 1.5 100 mW cm −2 illumination, attributed to the balance of competition between the increase of QD loading and suppression of interfacial recombination. This work highlights the combination of QDs with high absorption coefficient 1D architectures possessing efficient charge transport for constructing high efficiency solar cells. [ABSTRACT FROM AUTHOR]

Currently, most of CuS counter electrodes (CEs) used in quantum dot-sensitized solar cells (QDSSCs) are provided with a thickness of hundreds of nanometers or even several microns. Considering the CE with low thickness having many advantages, thin CuS films with thickness ranging from 47 nm below to 115 nm have been synthetized in this paper via chemical bath deposition (CBD) method with different bath concentrations. A power conversion efficiency (PCE) of 3.25% has been achieved utilizing CuS thin films a thickness of only 64 nm as CEs in QDSSCs without any structural optimization, which is higher than the value of the cell employing CuS CE with thickness of 2.8 μm. Electrochemical impedance spectroscopy, Tafel polarization, and two-point current-voltage measurements are used to investigate the electrocatalytic and conductive performance of CuS CEs with different thickness. Owing to the highest electrocatalytic capacity and good conductivity of the 64 nm-thick CuS CE, QDSSC assembled with this CE has reached relatively high PCE under one sun illumination (100 mW cm −2 , AM 1.5). In addition, cyclic voltammetry measurements indicate that the thin CuS CE has a good stability against the polysulfide electrolyte. [ABSTRACT FROM AUTHOR]

A low-cost, stable and efficient FeS thin film counter electrode (CE) was fabricated for quantum dot-sensitized solar cells (QDSSCs) by a facile chemical bath deposition method using different acidic hydroxyl solvents (ethanol, isopropanol, and tert-butanol) and triethanolamine. The choice of solvents greatly affected the surface morphology and thickness of FeS CEs. Apart from surface morphology, the increase in the atomic percentage of sulfur in tert-butanol and triethanolamine-mediated FeS also plays a crucial role in increasing the electrocatalytic activity of the CE. The QDSSC’s power conversion efficiency was 2.15%, which is attributed to the high fill factor (FF) of 0.443. The obtained PCE is far better than the previously reported value of 1.76% for FeS in QDDSC’s. Excellent stability of the photoelectric performance of the FeS CE is also demonstrated. The enhanced electrochemical performance of the interwoven FeS networks can be attributed to their unique morphology, which possesses a shorter diffusion length of the ions and easier transportation of the electrons. [ABSTRACT FROM AUTHOR]

A series of novel PbS/TiO 2 nanotubes was fabricated as counter electrodes (CEs) through a combination of anodic oxidation and successive ionic-layer adsorption and reaction methods. The photovoltaic-conversion efficiency of ZnO nanorods sensitized with CdS quantum dots using the optimized PbS(6)/TiO 2 CE increased by nearly 440.8% and 227.5% compared with the efficiency of nanorods using planar Pt and bare TiO 2 CE, respectively. Thus, the novel PbS/TiO 2 composite CE was a promising catalytic electrode with excellent electrocatalytic activity for the reduction of charge carriers in polysulfide electrolyte. [ABSTRACT FROM AUTHOR]

Copper sulfide (Cu 2 S) films were deposited on F-doped SnO 2 (FTO) substrates via the electrodeposition (ED) of copper (Cu) nanoparticles followed by sulfurization. The Cu nanoparticles were deposited on FTO substrates for various ED times ranging from 10 to 30 min at a constant −0.4 V. The FTO/Cu films consisted of flower-like nanoparticles comprised of randomly-clustering nanoflakes. The Cu nanoparticles electrodeposited for 10 min (FTO/Cu (10 min)) were dispersed sparsely over the FTO substrate, whereas the FTO/Cu (20 and 30 min) provided increased coverage. Unlike FTO/Cu 2 S (10 min), the FTO/Cu 2 S (20 and 30 min) consisted of vertically-standing large Cu 2 S nanosheets with numerous small nanosheets in between. This was attributed to the sufficient number of Cu seed nanoflakes, which not only facilitate ion transport of the redox couple but also increased the surface area, leading to significantly enhanced electrocatalytic activity. The quantum dot-sensitized solar cell (QD-SSC) with FTO/Cu 2 S (20 min) exhibited a significantly improved cell efficiency of 4.58%, compared to those with Pt and FTO/Cu 2 S (10 min). The QD-SSC with the FTO/Cu 2 S (30 min) showed similar cell efficiency to that with the FTO/Cu 2 S (20 min), despite the larger surface area because of its amorphous crystallographic structure offsetting the electrocatalytic activity. [ABSTRACT FROM AUTHOR]

An important component of quantum dot sensitized solar cells (QDSSC) is the counter electrode which mediates the regeneration of oxidized quantum dots by reducing the polysulphide electrolyte. However, design and synthesis of an efficient counter electrode material is a challenging task. Herein, we report the synthesis of a unique Cu 2 S nanohusks directly on FTO coated glass substrates by electrodeposition and used as a counter electrode in QDSSC. When these electrodes are used for the reduction of polysulfide electrolyte in QDSSC, they exhibit higher catalytic activity and photovoltaic performance as compared to the Platinum counter electrode. The power conversion efficiency of about 4.68% has been achieved by optimizing the deposition time of Cu 2 S. [ABSTRACT FROM AUTHOR]

Yttrium-doped ZnO nanorod arrays were applied to photoanodes of quantum dot-sensitized solar cells (QDSCs). The introduction of yttrium to ZnO nanostructures facilitates the growth of ZnO nanorods and increases the amount of QD deposition with a large surface area. Furthermore, lower electrical resistance and longer electron lifetime were achieved with yttrium-doping owing to fewer defects and trap sites on the surface of yttrium-doped ZnO nanorods. As a result, the conversion efficiency of 3.3% was achieved with the optimized concentration of yttrium. [ABSTRACT FROM AUTHOR]

Pursuit of an efficient strategy for quantum dot-sensitized photoanode has been a persistent objective for enhancing photovoltaic performances of quantum dot-sensitized solar cell (QDSC). We present here the fabrication of the indium sulfide (In 2 S 3 ) quantum dot-sensitized titanium dioxide (TiO 2 ) photoanode by combining successive ionic layer adsorption and reaction (SILAR) with solvothermal processes. The resultant QDSC consists of an In 2 S 3 sensitized TiO 2 photoanode, a liquid polysulfide electrolyte, and a Co 0.85 Se counter electrode. The optimized QDSC with photoanode prepared with the help of a SILAR method at 20 deposition cycles and solvothermal method yields a maximum power conversion efficiency of 1.39%. [ABSTRACT FROM AUTHOR]

Quantum dot-sensitized solar cells ( QDSSCs) were synthesized using CdS and CdSe quantum dots ( QDs) incorporated onto one-dimensional ZnO nanorods by successive ionic layer adsorption. In order to get the highest performance of the synthesized cell, the concentration of precursor QD solution and the number of deposition cycles in the QD solution were varied together. The photovoltaic performance of each cell was compared with the ultraviolet/visible absorption spectra and incident photon to current efficiency graphs. QDSSCs incorporating single-walled carbon nanotubes ( SWNTs), sprayed onto the substrate before deposition of the next layer, exhibited enhanced or decreased photocell efficiency compared to that of the pristine cell. In particular, a maximum rate increase of 17% was obtained with the solar cell containing SWNTs in CdSe QDs. [ABSTRACT FROM AUTHOR]

Quantum dot-sensitized solar cells ( QDSSCs) were synthesized using CdS and CdSe quantum dots ( QDs) incorporated onto one-dimensional ZnO nanorods by successive ionic layer adsorption. In order to get the highest performance of the synthesized cell, the concentration of precursor QD solution and the number of deposition cycles in the QD solution were varied together. The photovoltaic performance of each cell was compared with the ultraviolet/visible absorption spectra and incident photon to current efficiency graphs. QDSSCs incorporating single-walled carbon nanotubes ( SWNTs), sprayed onto the substrate before deposition of the next layer, exhibited enhanced or decreased photocell efficiency compared to that of the pristine cell. In particular, a maximum rate increase of 17% was obtained with the solar cell containing SWNTs in CdSe QDs. [ABSTRACT FROM AUTHOR]

In this paper, highly efficient nano peas like structure CuS film has been successfully employed in quantum dot sensitized solar cells (QDSSCs) for its highest catalytic activity at minimal cost. The CuS thin film electrode was deposited on fluorine-doped tin oxide (FTO) substrate by chemical bath deposition technique using urea at low deposition temperatures. This electrode elevated the short circuit current and fill factor in comparison to the frequently used Pt electrode. Moreover, electrochemical measurement data disclosed higher electrocatalytic activity toward polysulfide reduction. The CuS film exhibited an average particle size of 180–270 nm and film thickness of 825 nm. It also revealed superior J sc (13.87 mA/cm 2 ) and conversion efficiency of 4.01% which is remarkably higher than that of the Pt-based cell (1.07%). In addition, stability test conducted for both CuS and Pt-based cells for about 900 min at working conditions affirmed that the long-term stability of the CuS film decreased by 16.66% (4.02–3.35%), while that of the Pt based cell got elevated by 24.29% until 700 min, and consequently diminished by 8.27% from 700 to 900 min. [ABSTRACT FROM AUTHOR]

As an upconverter, lanthanide-doped NaYF 4 (Ln-NaYF 4 ) has been integrated into the photoanodes for quantum-dot sensitized solar cells. Compared with the solar cells with pure TiO 2 , the upconverter based solar cells exhibited a 17.6% increase in the photocurrent and a 20% increase in the power conversion efficiency. Furthermore, when the integrated Ln-NaYF 4 is pretreated by annealing, the resulting photoanode demonstrates an obvious improvement in the photocurrent generation and the power conversion efficiency due to the annealing-induced enhancement of the upconversion emission as well as the elimination of the defects allowing for efficiently reducing charge recombination. The best photovoltaic performance with a short-circuit current of 14.36 mA/cm 2 and a power conversion efficiency of 4.37% has been obtained with the solar cells containing the annealed upconverters. Both the solar cells integrated with the Ln-NaYF 4 pretreated by annealing or not demonstrate obvious photocurrent responses under the illumination of the NIR light. This finding demonstrates the feasibility of the combination of the up-converting materials with quantum dot-sensitized solar cells to extend the exploitation of the solar light to a wider range thus enabling the fabrication of highly efficient solar cells. [ABSTRACT FROM AUTHOR]

Nickel sulfide (NiS) thin film has been deposited on a fluorine-doped tin oxide substrate by a hydrothermal method using 3-mercaptopropionic acid and used as an efficient counter electrode (CE) for polysulfide redox reactions in quantum dot-sensitized solar cells (QDSSCs). NiS has low toxicity and environmental compatibility. In the present study, the size of the NiS nanoparticle increases with the hydrothermal deposition time. The performance of the QDSSCs is examined in detail using polysulfide electrolyte with the NiS CE. A TiO 2 /CdS/CdSe/ZnS-based QDSSC using the NiS CE shows enhanced photovoltaic performance with a power conversion efficiency (PCE) of 3.03%, which is superior to that of a cell with Pt CE (PCE 2.20%) under one sun illumination (AM 1.5, 100 mW cm −2 ). The improved photovoltaic performance of the NiS-based QDSSC may be attributed to a low charge transfer resistance (5.08 Ω) for the reduction of polysulfide on the CE, indicating greater electrocatalytic activity of the NiS. Electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel-polarization measurements were used to investigate the electrocatalytic activity of the NiS and Pt CEs. [ABSTRACT FROM AUTHOR]

Vacuum thermal evaporated Cu x S (VTE-Cu x S) film on fluorine-doped tin oxide substrate has been investigated as counter electrode (CE) for quantum dot-sensitized solar cells (QDSCs) with polysulfide electrolyte. The photovoltaic parameters of QDSCs show an obvious dependence on the annealing time of Cu x S film, and the maximum power conversion efficiency of 3.16 ± 0.05% under one sun illumination (100 mW cm −2 , AM 1.5 G) was obtained when the VTE-Cu x S CE was annealed at 270 °C for 300 s (VTE-Cu x S-300s CE). Electrochemical impedance spectroscopy, Tafel polarization, and cyclic voltammetry measurements have been employed to investigate the electrocatalytic activity of VTE-Cu x S-300s CE. The electrocatalytic activity of the VTE-Cu x S-300s CE is much higher than that of Pt CE, and is slightly higher than that of Cu 2 S CE in situ prepared on brass sheet. In particular, VTE-Cu x S-300s CE holds high diffusion velocity of S 2− /S n 2− in polysulfide electrolyte, and the stability of its electrocatalytic activity in polysulfide electrolyte is better than that of Pt and Brass-Cu 2 S CEs obviously. [ABSTRACT FROM AUTHOR]

Quantum dot-sensitized solar cells (QDSCs) have been attracting much attention due to their unique characteristics such as multiple exciton generation and a tunable band gap. Supporting materials of photoelectrodes for QDSCs like TiO 2 and ZnO are some of the most important parts because they absorb sensitizers and also function as photo-injected electron pathways. Particularly, ZnO has many advantages for the photoelectrodes of QDSCs. In this study, we investigated the effect of ammonia treatment on ZnO nanoflower-based QDSCs by varying the concentration of ammonia. The influence of ammonia treatment is discussed with respect to the power conversion efficiency from the J-V curve, electrochemical impedance spectroscopy (EIS), and other analyses. [ABSTRACT FROM AUTHOR]

Mesoporous TiO 2 microspheres with large surface area are synthesized by a hydrothermal reaction of titanium glycolate, and then introduced into CdS quantum dot-sensitized solar cell (QDSC). These mesoporous TiO 2 microspheres can not only increase the adsorption amount of quantum dots (QDs), but also possess effective light scattering ability due to the proper size, in comparison with traditional TiO 2 (P25). An overall power conversion efficiency of 2.63% is achieved by using these mesoporous TiO 2 microspheres as electrode in QDSC, significantly higher than that derived from P25 TiO 2 electrode. In addition, the photovoltaic behaviors of the materials are studied by surface photovoltage measurement to explain the excellent performance of QDSCs. [ABSTRACT FROM AUTHOR]

A PbS:Hg quantum dots-sensitized solar cell (QDSC) combined with a dye-sensitized solar cell (DSC) to harvest panchromatic solar spectrum from the visible light to the near IR is demonstrated. We use the filter to split the solar energy and access the total conversion efficiency. The DSC performing 12.4% under AM1.5G sunlight was able to generate 9.1% with a short-wave pass filter cutting off photons of wavelength longer than 650 nm. On the other hand, QDSC performing 5.58% generated 3.42% with the use of a long-wave pass filter transmitting beyond 630 nm. Calculated on the basis of transmitted light, DSC and QDSC performed 24.0% and 5.90%, leading to almost 13.1% of estimated total power conversion efficiency by harvesting the solar energy from visible light to the NIR. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) films were deposited on fluorine-doped tin oxide (FTO) glass substrates with the application of polysulfide redox reactions and a CuS counter electrode to fabricate CdS/CdSe quantum dot-sensitized solar cells (QDSCs). In the present study, ZnO nanoparticles were deposited in the interstices of the ZnO nanorods. The performance of the QDSCs was improved by the ZnO nanoparticle/ nanorod composite structure because the ZnO nanorods exhibit high electron transport, and while the ZnO nanoparticles have a large surface area for QD deposition. The ZnO nanoparticle/nanorod composite films represent a promising achievement for enhancing the conversion efficiency of QDSCs. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]