Quantum Dot-sensitized Solar Cells Research Articles

Mesoporous ZnO/TiO2 photoanodes for quantum dot sensitized solar cell

In the present work, different photoanodes, namely ZnO/TiO2 and bare TiO2 were deposited on fluorine-doped tin oxide (FTO) conductive glass substrate by the doctor blade method. CdS quantum dot was deposited on the photoanode by using the successive ionic layer adsorption and reaction (SILAR) method. In this, CuS was also coated on the FTO substrate which acts as the counter electrode. The structural, optical and electrical properties of deposited photoanodes and counter electrode were successfully investigated. The J-V characteristic and the other parameters of quantum dot sensitized solar cell (QDSSC) were analyzed by a using solar simulator under the illumination of a xenon short arc lamp an AM 1.5 G spectrum, having the light intensity of 100 mWcm−2. The power conversion efficiency of QDSSC using different photoanodes were compared. Due to the formation of energy barrier, ZnO/TiO2 using CdS QDs have higher efficiency (̴ 1.73%) as compared to bare TiO2 using CdS QDs (̴ 1.01%). It was found that ZnO/TiO2 based QDSSC exhibits 71% higher efficiency than that of TiO2 based QDSSC. The incident photon-to-current conversion efficiency (IPCE) obtained for ZnO/TiO2 electrode were approximately 46% (at 465 nm) and for bare TiO2 electrode around 34% (at 446 nm). The overall investigation supports the electron transport and enhanced performance of the ZnO/TiO2/CdS solar cell.

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.

Improving the Efficiency of Quantum Dot Sensitized Solar Cells beyond 15% via Secondary Deposition.

Low loading is one of the bottlenecks limiting the performance of quantum dot sensitized solar cells (QDSCs). Although previous QD secondary deposition relying on electrostatic interaction can improve QD loading, due to the introduction of new recombination centers, it is not capable of enhancing the photovoltage and fill factor. Herein, without the introduction of new recombination centers, a convenient QD secondary deposition approach is developed by creating new adsorption sites via the formation of a metal oxyhydroxide layer around QD presensitized photoanodes. MgCl2 solution treated Zn-Cu-In-S-Se (ZCISSe) QD sensitized TiO2 film electrodes have been chosen as a model device to investigate this secondary deposition approach. The experimental results demonstrate that additional 38% of the QDs are immobilized on the photoanode as a single layer. Due to the increased QD loading and concomitant enhanced light-harvesting capacity and reduced charge recombination, not only photocurrent but also photovoltage and fill factor have been remarkably enhanced. The average PCE of resulted ZCISSe QDSCs is boosted to 15.31% (Jsc = 26.52 mA cm-2, Voc = 0.802 V, FF = 0.720), from the original 13.54% (Jsc = 24.23 mA cm-2, Voc = 0.789 V, FF = 0.708). Furthermore, a new certified PCE record of 15.20% has been obtained for liquid-junction QDSCs.

Multifunctional nitrogen-doped graphene quantum dots incorporated into mesoporous TiO2 films for quantum dot-sensitized solar cells

Nitrogen-doped graphene quantum dots (N-GQDs) synthesized by a hydrothermal method were incorporated into TiO2 mesoporous films to boost the photovoltaic performance of quantum dot-sensitized solar cells (QDSSCs). Cadmium selenide quantum dots (CdSe QDs) were then deposited on the N-GQDs-incorporated TiO2 films using a successive ionic layer adsorption and reaction (SILAR) technique. The N-GQDs serve multiple functions for enhancing light-harvesting, facilitating electron transportation, and suppressing charge recombination. The non-zero gap N-GQDs both generate excitons as co-sensitizer and provide more adsorption sites for CdSe QDs. Furthermore, the N-GQDs provide efficient electron pathways between TiO2 nanoparticles and passivate the surface defects, giving rise to a high electron diffusion coefficient and long electron lifetime. The resulting QDSSC with the N-GQDs showed significantly improved power conversion efficiency (4.88%) compared to the QDSSC (3.92%) without N-GQDs.

Charge recombination suppressed CdSeS/CdSe/ZnS QDSSC design

The interest in quantum dot sensitized solar cells (QDSSC), which has theoretically proved to have up to 44% energy conversion efficiency in recent years, is growing rapidly. Although it has theoretically high efficiency value, PCE obtained in studies with QDSSCs is far from these values. This situation shows that there are many difficulties to be solved in QDSSC technology. One of the main challenges in QDSSC technology is irradiated load recombination occurring in QDSSC. For this reason, in this study, it is about using CdSeS QDs as an alternative to the most used CdS QDs in the literature in order to suppress the load recombination between TiO2 surface and electrolyte and QD surfaces. In the study, while CdS and CdSeS QDs were coated on the TiO2 surface with SILAR method, the previously synthesized CdSe QD was coated with chemical deep deposition method. Surfaces were last treated with ZnS QDs. An optimization study was carried out to determine the ideal number of CdSeS coatings for QDSSCs. As a result, the Jsc and Voc values for TiO2/CdSeS4/CdSe/ZnS QDSSCs were 8.799 mA/cm2 and 0.795 V, respectively, while the PCE value increased to 4.452%.

Zn‐Cu‐In‐S‐Se Quinary “Green” Alloyed Quantum‐Dot‐Sensitized Solar Cells with a Certified Efficiency of 14.4 %

AbstractThe photoelectronic properties of quantum dots (QDs) have a critical impact on the performance of quantum‐dot‐sensitized solar cells (QDSCs). Currently, I‐III‐VI group QDs have become the mainstream light‐harvesting materials in high‐performance QDSCs. However, it is still a great challenge to achieve satisfactory efficiency for light‐harvesting, charge extraction, and charge collection simultaneously in QDSCs. We design and prepare Zn0.4Cu0.7In1.0SxSe2−x (ZCISSe) quinary alloyed QDs by cation/anion co‐alloying strategy. The critical photoelectronic properties of target QDs, including band gap, conduction band energy level, and density of defect trap states, can be conveniently tailored. Experimental results demonstrate that the ZCISSe quinary alloyed QDs can achieve an ideal balance among light‐harvesting, photogenerated electron extraction, and charge‐collection efficiencies in QDSCs compared to its single anion or cation quaternary alloyed QD counterparts. Consequently, the quinary alloyed QDs boost the certified efficiency of QDSCs to 14.4 %, which is a new efficiency record for liquid‐junction QD solar cells.

Zn-Cu-In-S-Se Quinary "Green" Alloyed Quantum-Dot-Sensitized Solar Cells with a Certified Efficiency of 14.4 .

The photoelectronic properties of quantum dots (QDs) have a critical impact on the performance of quantum-dot-sensitized solar cells (QDSCs). Currently, I-III-VI group QDs have become the mainstream light-harvesting materials in high-performance QDSCs. However, it is still a great challenge to achieve satisfactory efficiency for light-harvesting, charge extraction, and charge collection simultaneously in QDSCs. We design and prepare Zn0.4 Cu0.7 In1.0 Sx Se2-x (ZCISSe) quinary alloyed QDs by cation/anion co-alloying strategy. The critical photoelectronic properties of target QDs, including band gap, conduction band energy level, and density of defect trap states, can be conveniently tailored. Experimental results demonstrate that the ZCISSe quinary alloyed QDs can achieve an ideal balance among light-harvesting, photogenerated electron extraction, and charge-collection efficiencies in QDSCs compared to its single anion or cation quaternary alloyed QD counterparts. Consequently, the quinary alloyed QDs boost the certified efficiency of QDSCs to 14.4 %, which is a new efficiency record for liquid-junction QD solar cells.

Application of TiO2 hollow spheres and ZnS/SiO2 double-passivaiting layers in the photoanode of the CdS/CdSe QDs sensitized solar cells for the efficiency enhancement

In this work quantum dot sensitized solar cells (QDSCs) with multilayer photoelectrodes were fabricated and investigated. The co-sensitization was carried out by CdS and CdSe quantum dots (QDs) layers and double passivation was performed by ZnS and SiO2 electron blocking films. Two kinds of TiO2 scaffolds in the forms of transparent TiO2 nanocrystals (NCs) and a double layer TiO2 NCs/TiO2 hollow spheres (HSs) were fabricated and utilized. The main CdSe sensitizing layer was deposited through a fast and effective chemical bath deposition (CBD) method in different conditions. Finally, a wide range of photoanodes were fabricated and applied in a conventional structure of the QDSCs. The results showed the maximized PCE of 3.65% for the QDSC with TiO2 NCs/CdS/CdSe (9 min)/ZnS/SiO2 photoelectrode. This efficiency was enhanced about 65% compared to the reference cell with CdSe and SiO2 free photoanode. For the double layer mesoporous TiO2 sublayer, it was shown that the QDSC with TiO2 NCs/HSs/CdS/CdSe (9 min)/ZnS/SiO2 multilayer photoanode demonstrated the maximum PCE of 6.1%. The mentioned efficiency was increased about 82%, 37% and 31% compared to the corresponding reference cells with TiO2 NCs/HSs/CdS/ZnS and TiO2 NCs/HSs/CdS/ZnS/SiO2 and TiO2 NCs/HSs/CdS/CdSe (9 min)/ZnS photoelectrodes, respectively.

Synergistic combination of TiO2-sol interconnecting-modified photoanode with alginate hydrogel-assisted electrolyte for quantum dots sensitized solar cells

Constructing the highly efficient and stable quasi-solid-state even solid-state devices is one of the most significant tendency in the field of quantum dots sensitized solar cells (QDSCs). Herein, highly efficient and stable quasi-solid-state (QS)-QDSCs devices were fabricated via synergistically combining the TiO2-sol interconnecting-modified photoanodes with alginate hydrogel (AH)-assisted electrolyte films. TiO2-sol binding agent could incorporate into the surface and voids of TiO2 particles, which increased the surface area and roughness for QDs loading and induced better connection between the neighboring particles. Meanwhile, the AH-assisted QS-electrolyte films possessed the crosslinking hydrogel network structure and exhibited the perfect interfacial contact with the modified TiO2 surface, thus enhancing the ion transport and redox reaction of polysulfide couple. Benefited from the synergistic effect of TiO2-sol modified photoanodes and alginate hydrogel (AH)-assisted electrolytes, a champion power conversion efficiency (PCE) of 8.87% for model ZnCuInSe (ZCISe) based QS-QDSCs was achieved with an enhancement of near 10% related to that of the devices based the pristine devices (8.01%), and very close to that of liquid-junction QDSCs (9.06%). Moreover, the constructed QS-QDSCs devices exhibit the excellent stability. This work thus provides a facile and effective strategy to achieve the QS-QDSCs devices with both of high efficiency and good stability.

Three-dimensional graphitic C3N4/CuS composite as the low-cost and high performance counter electrodes in QDSCs

As an essential working part in quantum dots sensitized solar cells (QDSCs), the counter electrode (CE) performs the function of extracting electrons form external circuit and catalyzing the reduction of electrolyte. To improve photovoltaic performance of cells, a new novel composite CE composed of graphitic C3N4 (g-C3N4) nanosheets and CuS nanoparticles is prepared on FTO glass via chemical bath deposition method. CuS nanoparticles can be successfully deposited on g-C3N4 nanosheets according to XRD, EDX, SEM and TEM results. A fast electron transport network can be constructed in 3D architecture formed with g-C3N4 nanosheets and CuS nanoparticles, which can afford multi-direction channels for electron transport and accessible catalytic active sites for reduction of polysulfide electrolyte. The synergistic effect of composite CE with continuous conductive network structure shows the excellent catalytic activity and fast electron mobilization. Electrochemical impedance spectrum reveals that the electrochemical property of g-C3N4/CuS composite CE in QDSCs has been changed significantly with the different composition of g-C3N4 and CuS, which is utilized to analyze why QDSC based on CN/30CuS CE shows the best photovoltaic properties of PCE of 5.10%. The new g-C3N4/CuS composite CE with the merits of low cost, easy processing and considerable photovoltaic performance is beneficial to large scale commercial use of three-generation solar cells.

Improved photovoltaic performance of solar cells co-sensitized with graphitic C3N4 and CdS quantum dots

In this work, C3N4 in graphite-like layer structure (graphitic C3N4, g-C3N4) prepared from melamine was applied into quantum dot-sensitized solar cells (QDSCs) as the co-sensitizer of CdS quantum dots (QDs). In the as-prepared photoanodes, g-C3N4 could improve the visible-light absorption and play a supporting role to improve the stability of TiO2 photoanode microstructure simultaneously. Through modifying the content of g-C3N4 in TiO2 photoanode, QDSCs based on 10 wt% g-C3N4 in TiO2 photoanode achieved the most optimal photovoltaic performance. Its short-circuit current density (Jsc) improved greatly, up to 14.08 mA/cm2, 72.5% higher than that of QDSCs without g-C3N4 and furthermore, the power conversion efficiency (PCE) was 4.65% with an increase of 106.7%. The mechanism of effect of g-C3N4 content on the photovoltaic performance of QDSC is investigated systematically through combining photoanodes microstructure characterization with electrochemical impedance (EIS) and current–voltage (J–V) curves analysis of cell samples.

State filling effects on photoluminescence and photovoltaic characteristic of aluminium-doped CdTe colloidal quantum dots stabilized in aqueous medium

CdTe and aluminium (Al)-doped CdTe (Al:CdTe QDs) colloidal quantum dots (QDs) were synthesized through an aqueous route. CdTe and Al:CdTe QDs colloidal quantum dots of different size were obtained by collecting the samples at different refluxing time. The size of the synthesized QDs collected after 6 h of refluxing time was measured to 3.3 and 4.8 nm for Al:CdTe QDs and CdTe QDs, respectively. The size shrinkages of Al:CdTe QDs were due to chlorine ions from AlCl3 precursor, which controls the growth kinetics of QDs and stabilizes the QDs in the aqueous phase. The size shrinkages of Al:CdTe QDs result in an increase of bandgap from 2.13 to 2.3 eV and congruently blue-shifted absorbance and emission spectra were discerned. The state filling effect, gradual filling of energy state, observed clearly in photoluminescence spectra of Al:CdTe QDs for samples collected after 30 min of refluxing time. We also fabricated Gratzel-type QDs-sensitized solar cells by loading CdTe and Al:CdTe QDs on mesoporous TiO2 photoanode. Photovoltaic efficiency is marginally increased (13%) from 0.45 to 0.51% for Al-doped CdTe QDs as compared to CdTe QDs.

Efficient quantum dot-sensitized solar cells through sulfur-rich carbon nitride modified electrolytes.

For quantum dot sensitized solar cells (QDSSCs), modifying conservative polysulfide electrolytes with polymer additives has been proven as an effective method to control charge recombination processes at the TiO2/QDs/electrolyte interface and to accomplish efficient cell devices. In this respect, the polysulfide electrolyte is modified with polymeric and sulfur-rich graphitic carbon nitride (SGCN) to enhance the photovoltaic performance of QDSSCs. For the first time, SGCN is used to passivate surface trap states and act as the steric hindrance between TiO2/QDs/electrolyte interfaces. The QDSSCs fabricated with GCN and SGCN additives exhibited higher efficiencies, especially improved short-circuit current (JSC) and fill factors (FFs) than those of the liquid electrolyte. Cu-In-S sensitized QDSSCs constructed with GCN and SGCN additives exhibited efficiencies of 6.73% and 7.13%, respectively, whereas the liquid electrolytes delivered an efficiency of 6.16%. Additionally, the applicability of SGCN additives in various Cu-based QDSSCs to enhance their photovoltaic performance is further verified using Cu-In-Se QDSSCs. An increase in the conversion efficiencies of QDSSCs with SGCN additives is possibly due to (1) their electron-rich surface which can act as an obstacle for electron-hole recombination, thereby suppressing the back-transfer of photo-induced electrons to the QD/electrolyte interface; (2) SGCN facilitates the reduction of Sn2- to S2- redox couple, thus providing holes towards the QDs/electrolyte more efficiently. Overall, this work provides an innovative and economic additive to modify polysulfide electrolytes, thereby controlling the TiO2/QDs/electrolyte interfaces of QDSSCs.

Constructing high-performance H3PW12O40/CoS2 counter electrodes for quantum dot sensitized solar cells by reducing the surface work function of CoS2.

A low cost H3PW12O40 (PW12)/CoS2 complex is prepared and used as a counter electrode (CE) to combine with sandwich quantum dot sensitized solar cells (QDSSCs) composed of a TiO2/CdS/CdSe/ZnS photoanode and polysulfide electrolyte to study their photovoltaic properties via a simple hydrothermal method. Under standard simulated sunlight, the photoelectric conversion efficiency (PCE) of 2%PW12 (PW12-2/CoS2) doped CEs was 6.29%, which was significantly 67.7% higher than those of QDSSCs based on undoped CoS2 CEs (3.75%). Due to the introduction of PW12, the nanoparticles forming the hollow structure of CoS2 changed from regular octahedra to rough nanoparticles, which increase the active sites. At the same time, the work function of CoS2 decorated with PW12 is decreased. This study and discovery demonstrate that POMs can be used to optimize CE materials and improve the photoelectric conversion efficiency of QDSSCs, which provide an experimental and theoretical basis for subsequent investigations.

Improving the electrocatalytic activity and stability of spinel sulfide counter electrodes by trimetallic synergy effects for quantum dot sensitized solar cells

Spinel trimetallic sulfide M0.5Ni0.5Co2S4 (M = Cu and Mn) nanostructures are designed and synthesized for the first time via a facile one-pot solvothermal strategy and used as efficient counter electrodes (CEs) for quantum dot sensitized solar cells (QDSSCs).

Enhancement of interface transportation for quantum dot solar cells using ultrathin InN by atomic layer deposition

Quantum dot-sensitized solar cells have gained rapid development which could produce potential applications. Although they have a theoretical photoelectric conversion efficiency of 44%, there is still a considerable gap in comparison with corresponding practical solar cells, which is mainly due to the fact that the interface transfer, stability and efficiency improvement are still facing some problems. In particular, the carrier recombination loss at the cell interface seriously hinders the quantum dot-sensitized solar cells from developing. In this work, an ultra-thin layer of InN prepared by plasma-enhanced atomic layer deposition is inserted into the FTO/TiO<sub>2</sub> interface of the photoanode of CdSeTe based quantum dot-sensitized solar cells to improve the performance of the photoanode structure, and physical mechanism behind the device is discussed. We first investigate the effects of different deposition temperatures (170, 200 and 230 ℃) on the cell performance of InN films. While the InN ultra-thin layer is deposited at 200 ℃, an enhancement of 16.9% in conversion efficiency is achieved as compared with the reference group. Then, the effects of different thickness (5, 10, and 15 cycles) on the cell are investigated at a fixed deposition temperature of 200 ℃. Additionally, an improvement of fill factor for the device after an introduction of InN layer is observed. This enhancement is further convinced by an apparent reduction of series resistance extracted by the Nyquist curve. The significant increase in fill factor indicates that the introduction of InN accelerates the extraction, transfer and separation of electrons, and reduces the possibility of photon-generated carriers recombination. However, the insertion of InN deposition temperature and thickness have a certain range of enhancement in the cell performance, and further investigation of the mechanism will be carried out.

Synthesis of Pb-doped CdS quantum dot using SILAR method on mesoporous TiO2 layer

This research focuses on the fabrication of CdS quantum dot-sensitized solar cells (QDSCs). CdS quantum dots (QDs) were fabricated on a mesoporous TiO2 electrode using a successive ion layer adsorption and reaction (SILAR) method and Pb doping concentrations (0, 2, 4, 10, 15, 20, 25 and 30 %mol) were varied. The change in optical properties of CdS QDs was found to be affected by Pb doping. The Pb-doped CdS QDSCs were determined under the illumination of 100 mWcm−2, which indicated the highest power conversion efficiency (PCE) was 1.73% at 20% Pb dopant.

Ball-milling treatment of cotton fiber for optimizing its derived carbon quantum dots

Due to the physical force of agate balls, many cracks on the surface of cotton fiber are caused by ball-milling treatment. Moreover, ball-milling changes the structure of cotton cellulose from crystalline to amorphous. These factors help increase the contact area of cotton fiber with active water and become more reactive in the hydrothermal process. Finally, ball- milling treatment improves the yield of carbon quantum dots (CQDs), which leads to a 10% increase in the power conversion efficiency of CQDs based quantum dot-sensitized solar cells. Besides, the fluorescence intensity of CQDs is doubled without changing its other characteristics because of the ball-milling treatment. Therefore, ball-milling could be adopted as an effective green method to optimize cotton derived CQDs.

In situ sulfidation of porous sponge-like CuO/SiW11Co into Cu2S/SiW11Co as stabilized and efficient counter electrode for quantum dot-sensitized solar cells.

Quantum dot-sensitized solar cells (QDSSCs), which are cost-effective, facilely prepared and environmentally friendly, are regarded as a promising third-generation photovoltaic technology, although the conversion efficiency of QDSSCs is still far lower than the theoretical efficiency (44%). Furthermore, the traditional Cu2S/brass counter electrode (CE) is susceptible to continuous corrosion from the polysulfide electrolyte, reducing the stability and electrocatalytic activity of the CE, thereby affecting cell performance. To enhance the stability of the Cu2S CE and make full use of its excellent catalytic properties, we used eco-friendly polyoxometalates (K6SiW11O39Co(ii) (H2O), SiW11Co) and porous sponge-like CuO as precursors to prepare a novel SiW11Co-doped high-efficiency Cu2S/SiW11Co CE on FTO by adopting the method of in situ sulfidation in the electrolyte. Electrochemical analysis revealed that the novel Cu2S/2%-SiW11Co (Cu2S-2) CE exhibits extremely high stability and electrocatalytic performance compared with other electrodes. Meanwhile, adding an appropriate amount of SiW11Co can inhibit charge recombination and improve cell performance. The CdS/CdSe co-sensitized QDSSCs assembled with the novel Cu2S-2 CE obtained a power conversion efficiency (PCE) of 5.94%, which was 20% more efficient than QDSSCs based on Cu2S/brass CE (4.96%). The method reported here puts forth a new direction for the preparation of efficient Cu2S counter electrodes.

Quantum Dot Sensitized Solar Cells: A Promising Avenue for Next-Generation Energy Conversion

By taking advantage of the unique qualities of colloidal quantum dots, quantum dot-sensitized solar cells (QDSSCs) provide a viable route for next-generation energy conversion while increasing the device's adaptability and light harvesting efficiency. This research aims to thoroughly examine the possibilities and difficulties associated with QDSSCs and offer information on their applications, methods for performance optimization, and policy ramifications. To assess the state-of-the-art research on QDSSCs, the technique systematically evaluates existing literature, including peer-reviewed articles, conference proceedings, and patents. Significant discoveries highlight developments in materials design, methods for fabricating devices, and potential integrations in consumer electronics, building-integrated photovoltaics, and off-grid applications. The policy implications underscore the necessity of regulatory frameworks to tackle environmental issues, set up guidelines and certification procedures, and foster global cooperation. In summary, this research highlights the importance of QDSSCs as a viable choice for sustainable energy conversion. It advocates for cooperative endeavors to surmount obstacles and expedite their integration into the renewable energy terrain.