Quantum Dot-sensitized Solar Cells Research Articles

Recent advances in the development of high efficiency quantum dot sensitized solar cells (QDSSCs): A review

Quantum dots play an important role in third-generation photovoltaics. The key focus on quantum dots is due to their cost effect, capacity to work in diffused light, ease of fabrication, light weight, and flexibility which pique curiosity to further research. The incorporation of quantum dots into photovoltaics results in theoretically high thermodynamic conversion efficiencies of up to 40%, but in practise, the efficiencies are lower than those of dye-sensitized solar cells. Recent developments of different components like photoanode, quantum dot sensitizer, electrolyte, and counter electrode were discussed in detail. It was observed that by changing the synthesis methods, the adhesion properties might vary, which leads to enhancing the photovoltaic properties such as power conversion efficiency (PCE), open circuit voltage (Voc), short circuit current (Jsc), and fill factor (FF). The first report on the efficiency of Quantum Dot Sensitized Solar Cells (QDSSCs) was 0.12%. As of today, the efficiency is reported as 18.1 %, and further, the researchers are working to improve the efficiency of QDSSCs.

Investigations on the interconnection between chemical reactions and experimental results of Zn-based quantum dots

ZnS-10H polytype, ZnO quantum dots, and mixed ZnS/ZnO obtained using zinc sulfate, zinc chloride, and zinc acetate as precursors, respectively. Nanoparticles, nanosheets, and nanoflowers were formed by changing zinc precursors and capping agents.

Atomic layer deposition of AlGaN alloy and its application in quantum dot sensitized solar cells

The role of plasma-enhanced atomic layer deposition growth of AlGaN ternary alloys on <i>c</i>-planar sapphire substrates and the preparation of quantum dot-sensitized solar cells are explored in this work. The interface between the film and the substrate as well as the band gap of AlGaN ternary alloys during atomic layer deposition is dependent on Al component. At high Al fraction, there appears a good interface between the AlGaN alloy film and the substrate, however, the interface becomes rough when the Al fraction is reduced. The AlGaN alloy prepared by atomic layer deposition has a high band gap, which is related to the oxygen content within the film. Subsequently, CdSe/AlGaN/ZnS and CdSe/ZnS/AlGaN structured cells are prepared and analyzed for quantum dot solar cells from AlGaN films with an AlN/GaN cycle ratio of 1∶1. It is found that AlGaN can modify and passivate quantum dots and TiO<sub>2</sub>, which can wrap and protect the structure of TiO<sub>2</sub> and CdSe quantum dot, thus avoiding the recombination of photo-generated carriers. This modification effect is also reflected in the improvement of open-circuit voltage, short-circuit current, filling factor and photovoltaic conversion efficiency of quantum dot solar cells. These factors are discussed in this work, trying to modify carrier transport characteristics of AlGaN films prepared by atomic layer deposition.

Surface engineering of two-dimensional hexagonal boron-nitride for optoelectronic devices.

Two-dimensional hexagonal boron nitride (2D h-BN) is being extensively studied in optoelectronic devices due to its electronic and photonic properties. However, the controlled optimization of h-BN's insulating properties is necessary to fully explore its potential in energy conversion and storage devices. In this work, we engineered the surface of h-BN nanoflakes via one-step in situ chemical functionalization using a liquid-phase exfoliation approach. The functionalized h-BN (F-h-BN) nanoflakes were subsequently dispersed on the surface of TiO2 to tune the TiO2/QDs interface of the optoelectronic device. The photoelectrochemical (PEC) devices based on TiO2/F-h-BN/QDs with optimized addition of carbon nanotubes (CNTs) and scattering layers showed 46% improvement compared to the control device (TiO2/QDs). This significant improvement is attributed to the reduced trap/carrier recombination and enhanced carrier injection rate of the TiO2-CNTs/F-h-BN/QDs photoanode. Furthermore, by employing an optimized TiO2-CNTs/F-h-BN/QDs photoanode, QDs-sensitized solar cells (QDSCs) yield an 18% improvement in photoconversion efficiency. This represents a potential and adaptability of our approach, and pathway to explore surface-engineered 2D materials to optimize the interface of solar energy conversion and other emerging optoelectronic devices.

Effect of the calcination temperature of the FTO/PbS cathode on the performance of a quantum dot-sensitized solar cell

<abstract> <p>As a cheaper alternative to the industrial Pt electrode used in quantum-sensitized solar cells, the electrophoresis process is employed to create the low-cost FTO/PbS cathode. For structural cubic and sizes ranging from 40 nm to 200 nm, structure and morphology were investigated using high-resolution scanning electron microscopy and X-ray diffraction. The conversion efficiency of solar cells is significantly impacted by the calcination temperatures of cathodes at 100 ℃, 150 ℃, 200 ℃, and 300 ℃ under vacuum. The FTO/PbS cathode electrode was therefore calcined at 150 ℃ with a maximum efficiency of 3.938%. This happens as a result of the complete fusion of PbS nanoparticles with crystal at 150 ℃, which reduces resistance and increases electron lifetime compared to other temperature combinations.</p> </abstract>

An investigation of the effects of ZnO inverse opal pore size in the composite of ZnO nanorods/ZnO inverse opal on the performance of quantum dot-sensitized solar cells.

A semiconductor oxide composite consisting of ZnO nanorods (NRs) and ZnO inverse opal (IO) was fabricated and used in the photoanode of quantum dot-sensitized solar cells (QDSSCs). Using polystyrene spheres 500, 800, 1000, and 1500 nm in diameter as the IO template, ZnO composites and corresponding QDSSCs with ZnO IOs of different pore sizes were fabricated. The oxide composite prepared with ZnO IOs of different pore sizes showed similar micro-morphologies; however, the photovoltaic performance of the QDSSCs based on these composites varied greatly. The QDSSCs based on the ZnO composite achieved high power conversion efficiencies (PCEs) of more than 6%, and the maximum PCE was 7.26% when the ZnO IO pore diameter in the composite was 800 nm. This resulted in very high PCE values for the QDSSCs using CdS/CdSe quantum dot sensitizers. With further interface modifications of NH4F and ZnS, the QDSSC achieved an even higher PCE value of 11.38%. Subsequently, the effects of ZnO IO pore size in the composite on QDSSC performance were investigated.

Co4N nanoparticles encapsulated in N-doped carbon framework for boosting electrochemical stability in quantum dot sensitized solar cells

Designing and constructing a delicate structure is an effective strategy to ensure the electrocatalytic stability of catalysts with excellent performance in quantum dot sensitized solar cells (QDSSCs) but remains challenging. Herein, ultrafine Co4N nanoparticles are encapsulated in a fish-scale-like N-doped carbon framework (Co4N@NC) in the form of Co–N–C bonds via a facile three-step method, including precursor construction, calcined carbonization and nitridation process. Notably, in the exquisite precursor construction process, the gelatinous chitosan induced by citric acid effectively bonds Co(Ⅱ) ions, and a fish-scale-like structure is designed under the action of template F127. The construction of this composite structure can increase contact with the electrolyte, favor electron conduction between particles, and improve the stability of the catalyst, thereby dramatically boosting the polysulfide reduction performance for QDSSCs. Co4N@NC is employed as the counter electrode (CE) of QDSSCs for the first time, its charge transfer resistance (Rct) is as low as 1.12Ω, and the power conversion efficiency of CdS/CdSe QDSSC reaches 5.54%, confirming extraordinary reduction activity towards Sn2−. Especially, compared with Co4N CE, Co4N@NC CE has better tolerance to polysulfide electrolytes and shows excellent electrochemical stability. This work provides a new strategy to improve the performance and stability of Co4N for the polysulfide reduction reaction.

Polyoxometalate-modified ternary copper-tungsten-sulfide nanocrystals as high-performance counter electrode materials for quantum dots-sensitized solar cells

The Cu2WS4/[Me2NH2]11[CeIII(PW11O39)2] (CWS/CeIII(PW11)2) composite is synthesized by simple solvothermal method and first applied as a counter electrode material in CdS/CdSe/ZnS-sensitized quantum dot sensitized solar cell (QDSSCs). Due to the co-existence of copper and tungsten in different valence states, the ternary CWS has more redox active sites than the binary Cu2S. Besides, the conduction band of CeIII(PW11)2 and CWS are well matched, so the electrons transport from CB of CeIII(PW11)2 to CWS is a favorable exothermic process. Brunauer-Emmett-Teller (BET), electrochemical impedance spectroscopy (EIS), Tafel-polarization test (Tafel), open-circuit voltage decay (OCVD) and cyclic voltammetry (CV) tests all confirmed that 4% CeIII(PW11)2/CWS (CWS-4) has the highest electrocatalytic activity. Under simulated sunlight, QDSSCs with CWS-4 CE delivered a power conversion efficiency (PCE) of 6.63% (Jsc = 23.42 mA cm−2, Voc = 0.62 V, FF = 0.46), which is 12% and 44% higher than QDSSCs with CWS and Cu2S CEs, respectively. CeIII(PW11)2, as an "electron-transport mediator" to compound with CWS can generate "shallow electron traps", increase active sites, and effectively inhibit the recombination of charges, thereby enhancing cell performance.

Dual Ligand Capped Quantum Dots Improving Loading Amount for High-Efficiency Quantum Dot-Sensitized Solar Cells

In quantum dot sensitized solar cells (QDSCs), high loading of high-quality QD sensitizers is a prerequisite for high photovoltaic performance. Herein, a facile and effective ligand design strategy to improve both the loading amount and optoelectronic performance of QD sensitizers is developed by decorating the QD surface with dual ligands of mercaptopropionic acid (MPA) and inorganic ligands (ILs). Experimental results demonstrate that the coexistence of ILs with MPA can not only reduce solvation energy that facilitates QD loading but also serve as effective cross-linkers for the reduction of interdot repulsion and formation of dense QD layers. Furthermore, various ILs, represented by pseudohalide SCN–, exhibit a great passivation effect on QD surfaces and suppress the defect trap states. Due to these benefits, Zn–Cu–In–S–Se (ZCISSe) QDSCs based on dual SCN/MPA ligands deliver a certified efficiency of 16.10%, which is a new record efficiency for liquid-junction QD solar cells.

Efficient triple-layer photoanode incorporated with nitrogen-doped TiO<sub>2</sub> nanocrystals for CdS quantum dot-sensitized solar cells

The Ceylon Journal of Science is a peer-reviewed journal published quarterly by the University of Peradeniya, Sri Lanka in March, June, September and December. It is aimed at publishing high quality research articles on topics related to different disciplines in Science. The journal accepts original research articles, book reviews, reviews and mini-reviews, short communications, opinions, research notes, and commentaries and notes. The Journal has its own website https://site.pdn.ac.lk/cjs/. The journal strictly adheres to publication ethics as emphasized by the Committee on Publication Ethics (COPE). It is indexed in Sri Lanka Journals Online (SLJOL), Directory of Open Access Journals (DOAJ), Google Scholar and Zoological Records. According to the Google Scholar;H5-Index: 12H5-Median: 15According to the Exaly (1970 – 2021);Impact Factor: 0.6 (top 19%)Extended IF: 0.6 (top 19%)H-Index: 8 (top 28%)Citations/paper: 1.42

Electrical properties of zinc sulfide and silver sulfide as binary salts in gel polymer electrolytes for quantum Dot-Sensitized solar cells

Gel polymer electrolytes (GPEs) with methyl cellulose (MC) polymer host have been prepared by solution casting. Succinonitrile (SN) is the plasticizer. ZnS and Ag2S are the sulfide salts added. The ZnS:Ag2S weight ratio has been varied. The crystallinity of MC:SN:co-ZnS-Ag2S:S has been investigated using X-ray Diffraction (XRD). The use of two cations from two different salts has decreased crystallinity of the GPEs and the. The MC:SN:(ZnS:Ag2S = 80:20):S GPE exhibited the lowest degree of crystallinity of 21.18 %. Ionic conductivity and dielectric studies have been studied using electrochemical impedance spectroscopy (EIS). MC:SN:(ZnS:Ag2S = 80:20):S electrolyte demonstrated the highest ionic conductivity at room temperature. The value is 6.93 × 10-2S.cm−1. The activation energy is 0.23 eV. The cell FTO/ZnOFe2O4/CdS/MC:SN:(ZnS:Ag2S = 80:20):S/GPE/Pt/FTO has been assembled and characterized. The efficiency obtained is 0.58 % with short current density (Jsc) of 2.15 mA.cm−2, open circuit voltage (Voc) of 0.48 V and fill factor (FF) of 0.56.

Black TiO2-Based Dual Photoanodes Boost the Efficiency of Quantum Dot-Sensitized Solar Cells to 11.7.

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.

Enhanced catalytic CuCo2Se4/g-C3N4 nano-composites as counter electrodes for high-performance quantum dot sensitized solar cells

Counter electrode (CE) plays a crucial role in collecting external circuit electrons and catalyzing electrolyte reduction in quantum dot sensitized solar cells (QDSSCs). Hence, inquiry into alternative CE materials with low cost and high catalytic activity will have a profound impact on realizing the commercialization of QDSSCs. Herein, we reported the in situ growth of CuCo2Se4 nanoparticles on graphitic carbon nitride g-C3N4 nanosheets by a simple hydrothermal method to form CuCo2Se4/g-C3N4 series composites and their first application as efficient CE materials in QDSSCs. The CuCo2Se4/g-C3N4 composite has a better hierarchical structure with g-C3N4 nanosheets as the support carrier, which is conducive to reducing the agglomeration effect of CuCo2Se4 nanoparticles, accelerating electrolyte diffusion and enhancing the stability of the material. In addition, the CuCo2Se4/CN-2 composite combines the excellent catalytic performance of the ternary selenide CuCo2Se4 with the better flexibility of g-C3N4 to exhibit prominent photovoltaic performance in QDSSCs, achieving a power conversion efficiency (PCE) as high as 8.48%, Jsc = 24.46 mA·cm−2, Voc = 0.635 V and FF = 0.55. It is 29% higher than the PCE (6.54%) of QDSSCs equipped with pure CuCo2Se4 CE. A series of measuring and testing approaches containing EIS, Tafel polarization and CV cycle experiments confirm that CuCo2Se4/CN-2 CE has much higher catalytic activity and stability, which further indicates that CuCo2Se4/CN-2 composite can become a potential electrode material in the field of solar cells.

Pompon-like NiCo2O4 nanospheres: a potential candidate for the counter electrode in quantum dot-sensitized solar cells

Pompon-like NiCo2O4 nanospheres: a potential candidate for the counter electrode in quantum dot-sensitized solar cells

Manifestation of the Enhanced Photovoltaic Performance in Eco-Friendly AgBiS2 Solar Cells Using Titanium Oxynitride as the Electron Transport Layer

In this study, titanium oxynitride with empirical composition of TiON is developed using a sol–gel and ammonia-gas-assisted thermal nitridation process. The obtained TiON phase is employed as the photoanodic electron transport layer (ETL) in a silver bismuth sulfide (AgBiS2) quantum-dot-sensitized solar cell (QDSSC) device and compared to a QDSSC consisting of commercial TiO2 as the ETL. The obtained X-ray photoelectron spectroscopy spectra and Mott–Schottky plots of the samples suggested that the valence and conduction bands of TiON are significantly shifted (EVB = 2.9 eV and ECB = −0.3 eV) with respect to that of TiO2 (EVB = 1.88 eV and ECB = −0.51 eV), which eventually decreased its band gap energy to 2.46 eV compared to TiO2 (3.2 eV). A decrease in the charge transfer resistance (Rct = 38.2 Ω) and improvement in carrier lifetime (τ = 5.3 ms) are observed in the developed TiON device. The work also endorses the use of eco-friendly green quantum dots of AgBiS2 as photoabsorbers in solar cells. Although the photovoltaic performance is not found to be greater, the demonstration of the enhanced performance of the TiON-based device with ∼50% enhancements, owing to its improved open circuit voltage and current density by 20 and 35%, is achieved in this work. Titanium oxynitride can, hence, be considered a suitable alternative to existing commercial TiO2 in all applications that involve solar energy conversion.

Near-infrared photoactive Ag-Zn-Ga-S-Se quantum dots for high-performance quantum dot-sensitized solar cells.

The high light-harvesting ability of quantum dots (QDs) plays an eminent role in the performance of solar cells. In this study, we synthesized Ag-Zn-Ga-S-Se-based alloyed QDs by colloidal hot injection and characterized them. The X-ray photoelectron spectrum analysis confirms the +1, +2, +3, -2, and -2 oxidation states of, respectively, Ag, Zn, Ga, S, and Se in the QDs, and the energy-dispersive X-ray spectrum analysis confirms the 1:1:1:1.5:1.5 stoichiometric ratio of, respectively, Ag, Zn, Ga, S, and Se. These two results indicate the formation of I-II-III-VI3-type alloyed crystals (AgZnGaS1.5Se1.5 nanocrystals). TEM image analysis reveals the QD nature of the synthesized Ag-Zn-Ga-S-Se nanocrystals. The X-ray diffraction pattern confirms the hexagonal structure. Due to the near-infrared light absorption capability, the synthesized QDs were used as the sensitizer to fabricate QDSCs. The fabricated QDSCs were characterized by using electrochemical impedance spectroscopy and photovoltaic performance studies. The fabricated QDSC have superior electrochemical activity with a photoconversion efficiency of 4.91%.

S, N Co-Doped Graphene Quantum Dots for Novel Quantum Dots Solar Cell

Graphene quantum dots (GQDs) have been extensively studied in recent days due to their excellent optical photo-absorption, low-cost synthesis and nontoxic nature. Furthermore, the optical and electronic properties of GQDs can be modulated by adding various dopant (like N, S, B, F, K, Si etc.) and can be used as a potential candidate for green solar energy material. Here, we have synthesized GQDs, N and N, S co-doped GQDs using low-cost hydrothermal process. Quantum dot sensitized solar cells (QDSSCs) were fabricated by sensitizing doped and undoped GQDs with ZnO nanorods. Current-Voltage characteristics of GQD sensitized ZnO NRs, N-GQD sensitized ZnO NRs and S, N-GQD sensitized ZnO NRs have been studied. The superior photovoltaic performance was obtained using S, N co-doped GQDs sensitized ZnO NRs with conversion efficiency [Formula: see text]%, which was 1.75 times higher than undoped GQD sensitized QDSSC device.

TiO2/CdS/CdSe quantum dots co-sensitized solar cell with the staggered-gap (type-II) heterojunctions for the enhanced photovoltaic performance

The effect of co-sensitization and ZnS passivation on the photovoltaic performance of CdS quantum dot sensitized solar cells (QDSSCs) were investigated. The deposition of CdS, CdSe quantum dots (QD) and ZnS passivation on TiO2 photoanode was carried out by successive ionic layer adsorption and reaction (SILAR) method. CdS/CdSe co-sensitization developed two staggered type-II heterojunctions at TiO2/CdS and CdS/CdSe interfaces and resulted a cascade energy band structure. This suitable band alignment facilitated the double charge transfer mechanism at each heterojunction and transported the electrons easily into the photoanode. The narrow bandgap sensitizers CdS and CdSe significantly improved the potential utilization of solar spectrum with more charge carrier generation. ZnS passivation on QD surface suppressed electrode/electrolyte interfacial charge recombination and facilitated more electron injection from QDs into TiO2 photoanode. The EDAX elemental mapping results inferred that CdS, CdSe and ZnS have efficiently covered the TiO2 surface. TiO2/CdS and CdS/CdSe interfaces and the amorphous nature of ZnS could be verified with HRTEM images. Hence, the co-sensitization and surface passivation played a significant role to enhance the PCE of CdS QDSSC from 1.9% to 4.05%.

Hydrothermal Synthesis of Se-Doped CuS Quantum Dots with Respect to the DW/EN Solvent Ratio and Application as a Counter Electrode for Quantum Dot-Sensitized Solar Cells

Hydrothermal Synthesis of Se-Doped CuS Quantum Dots with Respect to the DW/EN Solvent Ratio and Application as a Counter Electrode for Quantum Dot-Sensitized Solar Cells

Promoting the efficiency of quantum dots-based solar cells via the Cu:ZnSeS intermediate passivation layer

Constructing the interface passivation layer is of importance to accelerate the charge transfer and thus enhance the efficiency of quantum dots-sensitized solar cells (QDSCs). Here, an effective Cu:ZnSeS intermediate passivation layer (IPL), aiming at improving the charge transfer process, is fabricated on the surface of photoanodes via the facile successive ionic layer adsorption and reaction (SILAR) process. Electrical chemical analysis results exhibit that the Cu:ZnSeS IPL can efficiently hinder the charge recombination and accelerate the charge transport process due to the synergistic effect of ZnSeS alloy layer and Cu ions dopant. Meanwhile, the time-resolved photoluminescence (TRPL) spectroscopy demonstrates the Cu:ZnSeS IPL can not only reduce the surface traps but also accelerate hole capture. Importantly, the laser confocal Kelvin probe force microscopy (KPFM) measurement is first used to investigate the charge transport process via the change of surface potential in dark and under laser irradiation. In terms of the merits of Cu:ZnSeS IPL, the power conversion efficiency (PCE) of the resultant CdSeTe-based QDSCs reaches up to 9.46%, with an enhancement of 14%, compared to the traditional single ZnS passivation layer (∼8.32%). Besides, employing the Cu:ZnSeS intermediate passivation layer, the PCE of 11.64% was achieved, which is considered the highest reported in the reported CdSeTe QDSCs so far. This work demonstrates a facile and effective approach to modulating the charge transport process, thus enhancing the device performance.