CdSe Quantum Dot-sensitized Solar Cells Research Articles

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.

Sol-gel CdS layer for TiO2 nanorod-based quantum dots-sensitized solar cells

The CdS layer was essential for CdSe quantum dot-sensitized solar cells (QDSSCs) as the seed layer and energy barrier. Here, a novel sol–gel method was employed to prepare the CdS interlayer (SG-CdS) for TiO2 nanorod-based QDSSCs. Due to the sufficient reaction of the Cd and S sources in the sol–gel solution, SG-CdS exhibited fewer impurities than CdS produced by commonly used chemical bath deposition (CBD-CdS). QDSSCs with SG-CdS exhibited an open-circuit voltage of 490 mV, a short-circuit current density of 14.12 mA cm−2, and a fill factor of 0.35. The power conversion efficiency of the QDSSCs with SG-CdS was 2.48%, which was higher than that of the QDSSCs with CBD-CdS (2.02%). Moreover, electrochemical impedance spectroscopy showed that the QDSSCs with SG-CdS yielded a charge recombination resistance of 99.92 Ω at a bias voltage of −0.5 V, demonstrating less charge recombination than the QDSSCs with CBD-CdS (82.16 Ω). Therefore, the performance of the CdSe QDSSCs could be improved by reducing the impurities in CdS. This study revealed the advantages of SG-CdS in replacing CBD-CdS as the interlayer for charge transport, as well as good applicability with nanorod photoanodes in QDSSCs.

Enhanced photovoltaic performance of CdSe quantum dot-sensitized solar cells with Eu-doped TiO2 photoanode

Enhanced photovoltaic performance of CdSe quantum dot-sensitized solar cells with Eu-doped TiO2 photoanode

Effect of Different Ligands Coating on the Photovoltaic Performance of CdSe Quantum Dot-Sensitized Solar Cells

In this article, oleic acid (OA), oleylamine and tri-n-octylphosphine (OAm-TOP), and OA-TOP were used as ligands in the synthesis of CdSe quantum dots (QDs), respectively. Effect of three different ligands on the photovoltaic performance of CdSe QD-sensitized solar cells (QDSCs) is systematically investigated. Based on the results of UV-vis absorption spectra, it is confirmed that the absorption range is widen for CdSe QDs coated with OAm-TOP or OA-TOP compared with OA. Electrochemical impedance spectroscopy (EIS) study indicates that CdSe QDs synthesized using OAm-TOP or OA-TOP can better passivate the surface defects of QDs resulting in the improvement of photoelectric conversion efficiency (PCE) of devices. The optimized PCE of 3.6% was achieved for CdSe QDSCs modified with OAm-TOP.

Cadmium Selenide Quantum Dots for Solar Cell Applications: A Review.

Quantum dot-sensitized solar cells (QDSSCs) are significant energy-producing devices due to their remarkable capability to growing sunshine and produce many electrons/holes pairs, easy manufacturing, and low cost. However, their power conversion efficiency (4%) is usually worse than that of dye-sensitized solar cells (≤12%); this is mainly due to their narrow absorption areas and the charge recombination happening at the quantum dot/electrolyte and Ti /electrolyte interfaces. Thus, to raise the power conversion efficiency of QDSSC, new counter electrodes, working electrodes, sensitizers, and electrolytes are required. CdSe thin films have shown great potential for use in photodetectors, solar cells, biosensors, light-emitting diodes, and biomedical imaging systems. This article reviews the CdSe nanomaterials that have been recently used in QDSSCs as sensitizers. Their size, design, morphology, and density all noticeably influence the electron injection efficiency and light-harvesting capacity of these devices. A detailed overview of the development of QDSSCs is presented, including their basic principles, the synthesis methods for their CdSe quantum dots, and the device fabrication processes. Finally, the challenges and opportunities of realizing high-performance CdSe QDSSCs are discussed and some future directions are suggested.

Effect of linkers with different chemical structures on photovoltaic performance of CdSe quantum dot-sensitized solar cells

Introducing bifunctional linkers (COOH-R-SH) between TiO2 electrodes and quantum dots (QDs) was an effective apprIntroducing bifunctional linkers (COOH-R-SH) between TiO2 electrodes and quantum dots (QDs) was an effective approach in preparation of quantum dot-sensitized solar cells (QDSCs). Three types of linkers (4-mercaptobenzoic acid (MBA, R=phenyl), 3-thiophenecarboxylic acid (TPA, R=thiophene), and thioglycolic acid (TGA, R=alkyl)) were used to functionalize TiO2 electrodes and prepare TiO2/CdSe QDSCs with photoelectric conversion efficiency (PCE) of 5.50%, 4.59% and 4.85%, respectively. Various properties of modified and blank TiO2 electrodes, such as QDs loading, absorbance, work function, interfacial charge injection, recombination and their influence on PCE were investigated. In spite of low adsorption amounts of MBA on TiO2, the phenyl MBA-TiO2 electrodes obtained the highest Cd content due to regular arrangement and strong affinity to QDs. The FTIR spectra proved strong interactions between MBA and TiO2 electrodes, leading to fast electron injection from QDs to TiO2 electrodes. The electron injection rate in MBA-TiO2 electrodes was the same as blank-TiO2, larger than TGA- and TPA-ones. Work function of TiO2 electrodes modified by linkers could reduce several eV, in which the MBA-one decreased less, corresponding to the highest applied potential difference. The open-circuit voltage-decay measurement demonstrated that the MBA-TiO2 photoanodes had the least charge recombination. Enhanced light absorption capacity and fast electron injection rate were two key points for modified cell to improve short-circuit current, while low recombination and appropriate energy level positions increased open-circuit voltage. Those make MBA-TiO2 photoanodes obtain the best efficiency of 5.50%. We expected this work to guide the selection of linkers for design and optimization of photoanodes interface of QDSCs.oach in preparation of quantum dot-sensitized solar cells (QDSCs). Three types of linkers (4-mercaptobenzoic acid (MBA, R=phenyl), 3-thiophenecarboxylic acid (TPA, R=thiophene), and thioglycolic acid (TGA, R=alkyl)) were used to functionalize TiO2 electrodes and prepare TiO2/CdSe QDSCs with photoelectric conversion efficiency (PCE) of 5.50%, 4.59% and 4.85%, respectively. Various properties of modified and blank TiO2 electrodes, such as QDs loading, absorbance, work function, interfacial charge injection, recombination and their influence on PCE were investigated. In spite of low adsorption amounts of MBA on TiO2, the phenyl MBA-TiO2 electrodes obtained the highest Cd content due to regular arrangement and strong affinity to QDs. The FTIR spectra proved strong interactions between MBA and TiO2 electrodes, leading to fast electron injection from QDs to TiO2 electrodes. The electron injection rate in MBA-TiO2 electrodes was the same as blank-TiO2, larger than TGA- and TPA-ones. Work function of TiO2 electrodes modified by linkers could reduce several eV, in which the MBA-one decreased less, corresponding to the highest applied potential difference. The open-circuit voltage-decay measurement demonstrated that the MBA-TiO2 photoanodes had the least charge recombination. Enhanced light absorption capacity and fast electron injection rate were two key points for modified cell to improve short-circuit current, while low recombination and appropriate energy level positions increased open-circuit voltage. Those make MBA-TiO2 photoanodes obtain the best efficiency of 5.50%. We expected this work to guide the selection of linkers for design and optimization of photoanodes interface of QDSCs.

Voltage-assisted SILAR deposition of CdSe quantum dots to construct a high performance of ZnS/CdSe/ZnS quantum dot-sensitized solar cells

The charge recombination on the interfaces of TiO2/quantum dots (QDs)/electrolyte is a key factor limiting the efficiency of quantum dot-sensitized solar cells (QDSSCs). Construction of double-layer barrier structure of ZnS/QDs/ZnS is a vital strategy to suppress the interfacial charge recombination. However, a large lattice mismatch (12%) at CdSe/ZnS interfaces causes CdSe to grow slowly on TiO2/ZnS mesoporous film, weakening the interaction between QDs and mesoporous film, which reducing the efficiency of CdSe QDSSCs with double ZnS barrier layers. Applying a voltage of 2 V in successive ionic layer adsorption reaction (VASILAR) to create an electric field, which assists Cd2+ and SeSO32− ions rapidly diffuse into the TiO2/ZnS mesoporous film to react forming CdSe QDs at room temperature. Optimizing the number of CdSe QDs deposition layers and combine with ZnS double-layer barrier structure, a best PCE of 4.34% for ZnS/CdSe/ZnS QDSSCs is achieved. This study gives a fast and simple approach to inhibit interfacial charge recombination to construct high performance CdSe QDSSCs.

Exploring dynamics of resonance energy transfer in hybrid Quantum Dot Sensitized Solar Cells (QDSSC)

Graphene based nanomaterials are known to provide new avenues to improve semiconductor based light harvesting devices. This work makes use of graphene quantum dots (GQD) to improve the efficiency of a CdSe Quantum Dot Sensitized Solar Cell (QDSSC) by Förster Resonance Energy Transfer (FRET) mechanism. FRET describes non-radiative energy transfer between two adjacent molecules typically in range from 1 to 10 nm with one molecule as donor and other molecule as acceptor. If the acceptor is in close proximity of the excited donor, then their dipoles align resulting in transfer of excitation energy from donor to acceptor. Here graphene quantum dot acts as the energy donor to enhance light harvesting of CdSe quantum dot which acts as an acceptor in the hybrid solar cell. The introduction of GQD increases the efficiency of CdSe sensitized QDSSC from 0.18 to 0.28% showing an efficiency enhancement of 55%. The improved efficiency is mainly attributed to the 46% increase in current density of the GQD-CdSe solar cell compared to the CdSe QDSSC. The increased performance of the QDSSC owes to the existence of non-radiative energy transfer (FRET) between GQD and CdSe evident from photoluminescence (PL) quenching and lifetime measurements. This FRET system of GQD (donor)-CdSe (acceptor) shows an energy transfer of 48.7% providing new insights for selective light harvesting of the solar spectrum which can be utilised for various potential applications in future.

Voltage-assisted SILAR deposition of CdSe quantum dots into mesoporous TiO2 film for quantum dot-sensitized solar cells

CdSe quantum dots (QDs) grows slowly in mesoporous TiO2 film deriving from a large lattice mismatch (11%) and poor interaction between the two, which resulting the low power conversion efficiency (PCE) of quantum dot-sensitized solar cells (QDSSCs). An external voltage is applied in the successive ionic layer adsorption reaction (SILAR) process, which drives the Cd2+ and SeSO32− ions quickly diffused into the mesoporous TiO2 film and reacted to form CdSe QDs at room temperature. The CdSe QDSSCs yields a PCE of 3.27%. This work provides an efficient strategy to assemble QDs for enhancing the performance of QDSSCs.

Zeolitic-imidazolate frameworks derived Pt-free counter electrodes for high-performance quantum dot-sensitized solar cells.

Zeolitic-imidazole frameworks (ZIFs), as novel porous materials, are attracting much attention in several fields due to their special advantages such as large specific surface area, versatile porosity and well-connected networks. Here, we develop a porous ZIF-derived catalytic thin film, which was coated on the conducting glass as a counter electrode (CE) to substitute costly platinum for quantum dot-sensitized solar cells (QDSSCs). A ZIF layer is first prepared by coating ZIF-67 powders on the conducting glass, followed by the careful calcination treatments in sulfur vapour (sulfuration) or nitrogen gas (carbonization). The structure and morphologies of the derived porous film are characterized by the measurements of XRD, SEM and BET, and the electrochemical properties in the polysulfide solution are evaluated by the measurements of Tafel curves and electrochemical impedance spectroscopies. The derived porous film is used as a CE to fabricate QDSSC with CdSe quantum dot-sensitized TiO2 nanocrystalline thin film and the polysulfide solution. Compared with the photovoltaic performance of CdSe QDSSCs based on the CE prepared by the different sulfuration conditions, QDSSC based on the CE derived by the sulfuration for 30 min shows an excellent light-to-electric conversion efficiency of 3.77%, it is even higher than that of QDSSC based on Pt CE (2.98%). This work will open a new avenue to design a facile, low-cost and renewable CE for QDSSC.

Enhanced efficiency of quantum dot sensitized solar cells using Cu2O/TiO2 nanocomposite photoanodes

Several quantum dot sensitized solar cells (QDSSCs) were fabricated by doping Cu2O nanoparticles (NPs) into the TiO2 photoanode pastes in order to improve their efficiencies. The QDSSCs were made using the CuS counter electrode and sulfide/polysulfide electrolyte. The inclusion of Cu2O NPs in the photoanodes of both CdS and CdSe QDSSCs was found to increase the photocurrent and efficiency. The XPS analysis approved that the Cu2O particles were successfully impregnated on the TiO2 NPs. Results indicated that the photovoltaic parameters of the optimized CdSe cell (η = 3.01%, JSC = 10.2 mA cm−2, VOC = 0.59 V, FF = 0.50) were boosted compared with those of the reference cell which was free of Cu2O (η = 1.88%, JSC = 7.0 mA cm−2, VOC = 0.56 V, FF = 0.48) signifying about 60, 46 and 5% improvements in efficiency, current density and open-circuit voltage, respectively. The lowest intensity of the photoluminescence (PL) peak for the cell fabricated using 0.03% Cu2O doped TiO2 suggested that it had the least charge recombination and the easiest electron transfer which was confirmed by the J-V and efficiency data. The electrochemical impedance spectra (EIS) proved that the electron life time was considerably improved by approximately ten times in the optimized cell (τe = 60.0 ms) compared with that of the cell fabricated only using TiO2 (τe = 5.8 ms). Thus, addition of 0.03%wt Cu2O as a dopant was very appropriate to attain suitable photocurrent efficiency for the QDSSCs because it could be used in a minimum amount to improve the electron transport, drop the recombination and increase the cell efficiency.

Mesoporous nanoflakes Cu2S counter electrode prepared from three-dimensional ordered macroporous Cu film for quantum dot-sensitized solar cell

Mesoporous nanoflakes Cu2S 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 Cu2S CE can be controlled by the size of polystyrene microspheres. The optimized Cu2S CE shows a charge transfer resistance (RCT) as low as 1.24 Ω cm2, while the RCT of the Pt CE is 2250 Ω cm2. A CdSe QDSSC based on the mesoporous nanoflakes Cu2S CE achieved a power conversion efficiency of 6.01%, which was higher than that based on Pt CE (1.74%) and ordinary Cu2S 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 Cu2S CE. This work provides a new effective approach for the structure control of Cu2S CE for high-efficiency QDSSC.

Carrier transport dynamics in Mn-doped CdSe quantum dot sensitized solar cells

In this work quantum dot sensitized solar cells (QDSSCs) were fabricated with CdSe and Mn-doped CdSe quantum dots (QDs) using the SILAR method. QDSSCs based on Mn-doped CdSe QDs exhibited improved incident photon-to-electron conversion efficiency. Carrier transport dynamics in the QDSSCs were studied using the intensity modulated photocurrent/photovoltage spectroscopy technique, from which transport and recombination time constants could be derived. Compared to CdSe QDSSCs, Mn–CdSe QDSSCs exhibited shorter transport time constant, longer recombination time constant, longer diffusion length, and higher charge collection efficiency. These observations suggested that Mn doping in CdSe QDs could benefit the performance of solar cells based on such nanostructures.

A novel TiO2nanostructure as photoanode for highly efficient CdSe quantum dot-sensitized solar cells

For sensitized solar cells, photoanodes combining the advantages of TiO2nanoparticles (high specific surface area) and one-dimensional (1D) nanostructures (fast transport channels) are ideal for obtaining highly efficient sensitized solar cells.

Interfacial passivation mechanism of sulfide towards quantum dot-sensitized nanocrystalline thin films

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 Na2S 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 S2− 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.

Synthesis of Mn-doped zinc blende CdSe nanocrystals for quantum dot-sensitized solar cells

Mn-doped CdSe quantum dots (QDs) with a zinc blende structure were synthesized via a phosphine-free method in octadecene (ODE) and oleic acid. The structure, size, morphology, and optical property of the QDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–visible absorption spectra (UV–Vis), respectively. The QDs were assembled onto a microporous TiO2 photoanode by an ex situ ligand exchange route. Quantum dot-sensitized solar cells (QDSCs) based on the above-synthesized QDs and polysulfide electrolytes were fabricated. The photovoltaic performance and impedance of the CdSe and Mn-doped CdSe QDSCs were further investigated. An improvement in efficiency to 1.84 % was achieved as compared with 0.94 % for the QDSCs based on the pure CdSe QDs. The improvement was ascribed to the existence of long-lived high-energy doping levels on the large-sized Mn-doped CdSe QDs, which provides a significant driving force for faster charge separation and electron transfer.

One-Step Electrodeposited Nickel Cobalt Sulfide Electrocatalyst for Quantum Dot-Sensitized Solar Cells

This paper reports a new facile one-step cyclic voltammetry electrochemical co-depositing method to prepare a novel nickel cobalt sulfide (NiCo2S4) counter electrode (CE) on a FTO glass substrate as well as its promising application as an efficient CE in CdSe quantum dot-sensitized solar cells (QD-SSCs). The QD-SSCs fabricated using NiCo2S4 as a CE exhibited a significantly enhanced short circuit current and fill factor, resulting in a significantly improved overall energy conversion efficiency (3.67%) compared to those with the Pt (2.26%), CoS (2.70%) and NiS (2.56%) CEs under 1 sun illumination. This can be attributed to the significantly enhanced electrocatalytic activity and superior electrical conductivity of the NiCo2S4 and the excellent electrical contact at the electrodeposited NiCo2S4/FTO interface.

Enhanced performance of branched TiO2 nanorod based Mn-doped CdS and Mn-doped CdSe quantum dot-sensitized solar cell

TiO2 branched nanostructures could be efficient as photoanodes for quantum dot-sensitized solar cells (QDSCs) due to their large surface area for QD deposition. In this study, Mn-doped CdS/Mn-doped CdSe deposited branched TiO2 nanorods were fabricated to enhance the photovoltaic performance of QDSCs. Mn doping in CdS and CdSe retards the recombination losses of electrons, while branched TiO2 nanorods facilitate effective electron transport and compensate for the low surface area of the nanorod structure. As a result, the charge-transfer resistance (RCT), electron lifetime (τe), and the amount of QD deposition were significantly improved with branched TiO2 nanorod based Mn-doped CdS/Mn-doped CdSe quantum dot-sensitized solar cell.

CdSe Quantum Dot-Sensitized Solar Cell: Effect of Size and Attach Mode of Quantum Dot

Different size of colloidal CdSe quantum dot (QD) was synthesized through a simple solvothermal route and their structural, morphological and optical properties were characterized with X-ray diffraction (XRD), transmission electron microscope (TEM), UV-visible absorption spectroscopy and fluorescence spectrometer. XRD and TEM measurement confirmed the formation of CdSe QDs. The red shift of absorption and fluorescence peaks indicated that the size of CdSe QDs increased with prolonging reaction time. The size of QDs varied from 2.2 nm to 3.4 nm by varying reaction time from 1 h to 7 h. The absorption spectra of CdSe/TiO2 electrodes proved that the loading of CdSe QDs on TiO2 can be greatly improved by MPA pretreatment. The effect of size of CdSe QDs on the performance of CdSe QDs sensitized solar cells was investigated. Due to the change of absorption range in the visible region and the conduction band shift for different size of CdSe, the photo-electric power conversion efficiency first increased and then decreased with increasing size of CdSe. The devices fabricated with 3.1 nm diameter CdSe nanoparticles exhibited the highest conversion efficiency of 0.70% under AM 1.5 G irradiation (100 mW cm−2).

Influence of deposition strategies on CdSe quantum dot-sensitized solar cells: a comparison between successive ionic layer adsorption and reaction and chemical bath deposition

Appreciable influences of deposition strategies on the assembly of QDs and the performance of the resultant QDSCs were highlighted.