Research

11 pages, 3490 KiB

Open AccessArticle

Annealing-Temperature Dependent Carrier-Transportation in ZnO/PbS Quantum Dot Solar Cells Fabricated Using Liquid-Phase Ligand Exchange Methods

by Akihiro Takahashi, Haibin Wang, Takeshi Fukuda, Norihiko Kamata, Takaya Kubo and Hiroshi Segawa

Energies 2020, 13(19), 5037; https://doi.org/10.3390/en13195037 - 24 Sep 2020

Cited by 4 | Viewed by 2702

Abstract

We constructed ZnO/PbS quantum dot (QD) heterojunction solar cells using liquid-phase ligand exchange methods. Colloidal QD solutions deposited on ZnO-dense layers were treated at different temperatures to systematically study how thermal annealing temperature affected carrier transport properties. The surface of the layers became [...] Read more.

We constructed ZnO/PbS quantum dot (QD) heterojunction solar cells using liquid-phase ligand exchange methods. Colloidal QD solutions deposited on ZnO-dense layers were treated at different temperatures to systematically study how thermal annealing temperature affected carrier transport properties. The surface of the layers became dense and smooth as the temperature approached approximately 80 °C. The morphology of layers became rough for higher temperatures, causing large grain-forming PbS QD aggregation. The number of defect states in the layers indicated a valley-shaped profile with a minimum of 80 °C. This temperature dependence was closely related to the amount of residual n-butylamine complexes in the PbS QD layers and the active layer morphology. The resulting carrier diffusion length obtained on the active layers treated at 80 °C reached approximately 430 nm. The solar cells with a 430-nm-thick active layer produced a power conversion efficiency (PCE) of 11.3%. An even higher PCE is expected in solar cells fabricated under optimal annealing conditions. Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Graphical abstract

14 pages, 5769 KiB

Open AccessArticle

Density Functional Theory-Based Molecular Modeling: Verification of Decisive Roles of Van der Waals Aggregation of Triiodide Ions for Effective Electron Transfer in Wet-Type N3-Dye-Sensitized Solar Cells

by Susumu Yanagisawa and Shozo Yanagida

Energies 2020, 13(11), 3027; https://doi.org/10.3390/en13113027 - 11 Jun 2020

Cited by 6 | Viewed by 2883

Abstract

Density functional theory-based molecular modeling (DFT/MM) validates that KI and I₂ undergo exothermic van der Waals (vdW) aggregation in acetonitrile (AN) or in the presence of 4-tert-butylpyridine (TBP), forming potassium triiodide (KI₃) and, further mutual vdW aggregation leads to the [...] Read more.

Density functional theory-based molecular modeling (DFT/MM) validates that KI and I₂ undergo exothermic van der Waals (vdW) aggregation in acetonitrile (AN) or in the presence of 4-tert-butylpyridine (TBP), forming potassium triiodide (KI₃) and, further mutual vdW aggregation leads to the formation of (KI₃)₂ and AN, (KI₃)₂ and (AN)₂ and (KI₃)₂ and TBP in the AN-based Dye sensitized solar cells (DSSC) electrolytes. All KI₃ aggregates have a very low energy gap, 0.17 eV, 0.14 eV and 0.05 eV of lowest unoccupied molecular orbital (LUMO) + 1 and LUMO, respectively, verifying efficient electron diffusion in μm-thick DSSC electrolytes. Hydrogen-bonding aggregation of anatase TiO₂ model, Ti₉O₁₈H and OH, with N3 (proton) dye is also validated by DFT/MM, and the energy structure verifies unidirectional electron flow from highest occupied molecular orbital (HOMO) on thiocyanide (SCN) groups of N3 dye to LUMO on the TiO₂ model at the aggregates. Further, DFT/MM for the aggregation of K⁺I₃⁻ with N3 verifies the most exothermic formation of the aggregate of N3 (proton) and K⁺I₃⁻. The UV-Vis spectra of N3 (proton) and K⁺I₃⁻ is consistent with reported incident photocurrent efficiency (IPCE) action spectra (λ = 450–800 nm) of N3-sensitized DSSC, verifying that the N3 dye of N3 (proton) and K⁺I₃⁻ becomes an effective sensitizer in the anode / TiO₂ / N3 (proton) / KI/I₂ / acetonitrile (AN) / cathode structured DSSC. The energy structure of LUMO and LUMO + 1 of the aggregates, Ti₉O₁₈H and OH and N3 (proton), N3 and K⁺I₃⁻, (KI₃)₂ and AN and (KI₃)₂ and TBP verifies high IPCE photocurrent and effective electron diffusion via KI₃-aggregates in the DSSC of Ti₉O₁₈H and OH and N3 (proton) and K⁺I₃⁻. Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Graphical abstract

10 pages, 3723 KiB

Open AccessArticle

Magnetron Sputtered Electron Blocking Layer as an Efficient Method to Improve Dye-Sensitized Solar Cell Performance

by Dariusz Augustowski, Paweł Kwaśnicki, Justyna Dziedzic and Jakub Rysz

Energies 2020, 13(11), 2690; https://doi.org/10.3390/en13112690 - 27 May 2020

Cited by 4 | Viewed by 1991

Abstract

The main efficiency loss is caused by an intensive recombination process at the interface of fluorine-doped tin oxide (FTO) and electrolyte in dye-sensitized solar cells. Electrons from the photoanode can be injected back to the redox electrolyte and, thus, can reduce the short [...] Read more.

The main efficiency loss is caused by an intensive recombination process at the interface of fluorine-doped tin oxide (FTO) and electrolyte in dye-sensitized solar cells. Electrons from the photoanode can be injected back to the redox electrolyte and, thus, can reduce the short circuit current. To avoid this, the effect of the electron blocking layer (EBL) was studied. An additional thin film of magnetron sputtered TiO₂ was deposited directly onto the FTO glass. The obtained EBL was characterized by atomic force microscopy, scanning electron microscopy, optical profilometry, energy dispersive spectroscopy, Raman spectroscopy and UV-VIS-NIR spectrophotometry. The results of the current–voltage characteristics showed that both the short circuit current (I_sc) and fill factor (FF) increased. Compared to traditional dye-sensitized solar cell (DSSC) architecture, the power conversion efficiency (η) increased from 4.67% to 6.07% for samples with a 7 × 7 mm² active area and from 2.62% to 3.06% for those with an area of 7 × 80 mm². Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Figure 1

8 pages, 1384 KiB

Open AccessArticle

3D Structural Optimization of Zinc Phthalocyanine-Based Sensitizers for Enhancement of Open-Circuit Voltage of Dye-Sensitized Solar Cells

by Takuro Ikeuchi, Ryota Kudo, Yu Kitazawa, Shogo Mori and Mutsumi Kimura

Energies 2020, 13(9), 2288; https://doi.org/10.3390/en13092288 - 05 May 2020

Cited by 3 | Viewed by 1864

Abstract

We designed and synthesized two zinc phthalocyanine sensitizers (PcS27 and PcS28), substituted with branched or cyclic alkoxy chains, to investigate the structural effect of peripheral alkyl chains on the performance of dye-sensitized TiO₂ solar cells. The bulky cyclic alkyl chains [...] Read more.

We designed and synthesized two zinc phthalocyanine sensitizers (PcS27 and PcS28), substituted with branched or cyclic alkoxy chains, to investigate the structural effect of peripheral alkyl chains on the performance of dye-sensitized TiO₂ solar cells. The bulky cyclic alkyl chains of PcS28 decreased the adsorption density of PcS28 on the TiO₂ electrode, while the terminal branches of alkoxy chains of PcS27 did not influence the adsorption density in comparison to the previously published PcS20 with linear alkoxy chains. Under one sun conditions, PcS27 cells exhibited higher open-circuit voltage but a slightly lower energy conversion efficiency, 6.0% less than PcS20. These results suggest that the small alternation of alkoxy chains resulted in decreasing electron pushing ability of peripheral phenoxy units, giving lower short-circuit current. Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Figure 1

14 pages, 7684 KiB

Open AccessArticle

Study of How Photoelectrodes Modified by TiO₂/Ag Nanofibers in Various Structures Enhance the Efficiency of Dye-Sensitized Solar Cells under Low Illumination

by Yu-Hsun Nien, Huang-Hua Chen, Hui-Hsuan Hsu, Manjunath Rangasamy, Geng-Ming Hu, Zhen-Rong Yong, Po-Yu Kuo, Jung-Chuan Chou, Chih-Hsien Lai, Cheng-Chu Ko and Jun-Xiang Chang

Energies 2020, 13(9), 2248; https://doi.org/10.3390/en13092248 - 04 May 2020

Cited by 22 | Viewed by 2662

Abstract

Dye-sensitized solar cells (DSSCs) are low-cost solar cells belonging to the thin-film photovoltaic cell type. In this study, we studied the photovoltaic performances of DSSCs based on titanium dioxide (TiO₂) nanofibers (NFs) containing silver (Ag) nanoparticles (NPs) under low illumination. We [...] Read more.

Dye-sensitized solar cells (DSSCs) are low-cost solar cells belonging to the thin-film photovoltaic cell type. In this study, we studied the photovoltaic performances of DSSCs based on titanium dioxide (TiO₂) nanofibers (NFs) containing silver (Ag) nanoparticles (NPs) under low illumination. We used the sol-gel method with the electrospinning technique to prepare the TiO₂ NFs containing Ag NPs. Herein, we used two ways to add TiO₂/Ag NFs to modify the photoelectrode successfully and enhance the performance of DSSCs. One way was that the TiO₂/Ag NFs were mixed with pristine TiO₂; the other way was that the TiO₂/Ag NFs were seeded beside the TiO₂ colloid layer as an additional layer on the photoelectrode of the DSSC. According to this experiment, the photovoltaic conversion efficiency of the DSSC which had TiO₂/Ag NF seeded as an additional layer on the photoelectrode (5.13%) was increased by 28% compared to the DSSC without the photoelectrode modification (3.99%). This was due to the suppression of electron recombination and the more effective utilization of the light radiation by adding the TiO₂/Ag NFs. Because of the good conductivity of Ag, the electrons were quickly transported and electron recombination was reduced. In addition, the photovoltaic conversion efficiency of the DSSC which had TiO₂/Ag NF seeded as an additional layer on the photoelectrode increased from 5.13% to 6.23% during the decrease in illumination from 100 mW/cm² to 30 mW/cm²; however, its photovoltaic conversion efficiency decreased to 5.31% when the illumination was lowered to 10 mW/cm². Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Figure 1

12 pages, 3180 KiB

Open AccessFeature PaperArticle

Quantification of Dyes Generating Photocurrent and/or Photoluminescence in Dye-Sensitized Solar Cells Using Laser Scanning Microscopy

by Masaaki Mitsui, Kyosuke Mori and Reina Kobayashi

Energies 2020, 13(8), 1866; https://doi.org/10.3390/en13081866 - 11 Apr 2020

Cited by 3 | Viewed by 2256

Abstract

Photoconversion processes such as electron injection (photooxidation) and dye regeneration (reduction) in dye-sensitized solar cells (DSSCs) occur at considerably inhomogeneous semiconductor/dye/electrolyte interfaces, implying a very high heterogeneity of interfacial photoconversion kinetics. Herein, we present a temporally and spatially resolved investigation of DSSCs comprising [...] Read more.

Photoconversion processes such as electron injection (photooxidation) and dye regeneration (reduction) in dye-sensitized solar cells (DSSCs) occur at considerably inhomogeneous semiconductor/dye/electrolyte interfaces, implying a very high heterogeneity of interfacial photoconversion kinetics. Herein, we present a temporally and spatially resolved investigation of DSSCs comprising a cover glass photoanode with a 100-nm thick TiO₂ layer loaded with the metal-free organic dye sensitizer MK-2, which is performed by employing laser scanning microscopy (LSM) for the simultaneous measurement of the photocurrent (PC) and photoluminescence (PL) of DSSCs under short-circuit conditions. Analysis of PL decay curves and the excitation rate dependences of PC and PL obtained for local (or submicrometric) areas of the MK-2-DSSC allows disclosing and quantifying three types of dyes coexisting in the DSSCs: (i) a dye that only generates PC (“PC-dye,” 75% of total dye molecules in the DSSC), (ii) a dye that generates both PC and PL (“PCPL-dye,” 20%), and (iii) a dye that only generates PL (“PL-dye,” 5%). Considering recent theoretical reports on cyanoacrylic dyes, we propose that the PC-dye and the PCPL-dye are covalently bound on a TiO₂ surface with different adsorption modes (presumably bidentate and tridentate bridging configurations), whereas the PL-dye is noncovalently trapped within a mesoporous TiO₂ film. Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Graphical abstract

13 pages, 5221 KiB

Open AccessArticle

“Paper Dye-Sensitized Solar Cell” Based on Carbon-Nanotube-Composite Papers

by Yuya Ogata, Kodai Iguchi and Takahide Oya

Energies 2020, 13(1), 57; https://doi.org/10.3390/en13010057 - 20 Dec 2019

Cited by 9 | Viewed by 2737

Abstract

We propose a paper solar cell based on carbon nanotube (CNT)-composite papers. To fabricate this cell, we use dye-sensitized solar cells (DSCs) for generating power through the redox reaction of dyes in conjunction with CNT-composite papers, which are composite materials containing CNTs and [...] Read more.

We propose a paper solar cell based on carbon nanotube (CNT)-composite papers. To fabricate this cell, we use dye-sensitized solar cells (DSCs) for generating power through the redox reaction of dyes in conjunction with CNT-composite papers, which are composite materials containing CNTs and pulp (raw paper material) that can be fabricated easily by using a method based on the Japanese washi papermaking technique. The demand for CNT applications is expected to increase due to their high conductivity and metallic or semiconducting characteristics. This CNT-composite paper can also have metallic or semiconducting characteristics based on the contained CNTs in the composite paper. We previously fabricated a DSC that generates electricity by using CNT-composite papers stacked in a typical DSC structure. However, the conversion efficiency of this DSC was just 0.188%, which is not practical. To overcome this low power generation issue, we tried improving the DSC structure by applying electrodes to the CNT-composite papers in grid patterns for efficient current collection and applying an optimally mixed dye for efficient electron excitation. Results showed that the conversion efficiency improved to 0.58%. Moreover, we demonstrated that using a mixed dye can improve the conversion efficiency of the paper DSC. We expect these types of CNT-composite papers to be used as material for new DSCs. Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Graphical abstract

13 pages, 5809 KiB

Open AccessArticle

Dye-Sensitized Solar Cells Using Aluminum-Doped Zinc Oxide/Titanium Dioxide Photoanodes in Parallel

by Jung-Chuan Chou, Cheng-Chu Ko, Jun-Xiang Chang, Chih-Hsien Lai, Yu-Hsun Nien, Po-Yu Kuo, Huang-Hua Chen, Hui-Hsuan Hsu and Geng-Ming Hu

Energies 2019, 12(18), 3469; https://doi.org/10.3390/en12183469 - 09 Sep 2019

Cited by 9 | Viewed by 4171

Abstract

In this study, both zinc oxide (ZnO) nanorods and aluminum-doped zinc oxide (AZO) nanosheets were deposited by hydrothermal growth on fluorine-doped tin oxide (FTO) glass. After a photoanode was added to ZnO nanorods or AZO nanosheets, the photovoltaic conversion efficiency (PCE) increased due [...] Read more.

In this study, both zinc oxide (ZnO) nanorods and aluminum-doped zinc oxide (AZO) nanosheets were deposited by hydrothermal growth on fluorine-doped tin oxide (FTO) glass. After a photoanode was added to ZnO nanorods or AZO nanosheets, the photovoltaic conversion efficiency (PCE) increased due to improved electron transport and enhanced dye absorption. The improvement in electron transport was verified by electrochemical impedance spectroscopy (EIS), and the increase in dye absorption was verified by ultraviolet-visible spectroscopy. Both of these factors facilitated an increase in PCE. Parameters for dye-sensitized solar cells (DSSCs) using ZnO nanorods/TiO₂ and AZO nanosheets/TiO₂ photoanodes were tested and the results were recorded using EIS. The results indicated that the addition of the ZnO nanorods increased the short-circuit current density (J_sc) from 9.07 mA/cm² to 10.91 mA/cm², the open circuit voltage (V_oc) from 0.68 V to 0.70 V, and the PCE from 3.70% to 4.73%, respectively. When the DSSCs were produced in a parallel silver-grid device, the results showed that PCE could be increased from 3.67% to 4.04% due to the reduction in connection resistance. Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Figure 1

Review

Jump to: Research, Other

14 pages, 4330 KiB

Open AccessFeature PaperReview

Interfacial Charge-Transfer Transitions for Direct Charge-Separation Photovoltaics

by Jun-ichi Fujisawa

Energies 2020, 13(10), 2521; https://doi.org/10.3390/en13102521 - 15 May 2020

Cited by 17 | Viewed by 2274

Abstract

Photoinduced charge separation (PCS) plays an essential role in various solar energy conversions such as photovoltaic conversion in solar cells. Usually, PCS in solar cells occurs stepwise via solar energy absorption by light absorbers (dyes, inorganic semiconductors, etc.) and the subsequent charge transfer [...] Read more.

Photoinduced charge separation (PCS) plays an essential role in various solar energy conversions such as photovoltaic conversion in solar cells. Usually, PCS in solar cells occurs stepwise via solar energy absorption by light absorbers (dyes, inorganic semiconductors, etc.) and the subsequent charge transfer at heterogeneous interfaces. Unfortunately, this two-step PCS occurs with a relatively large amount of the energy loss (at least ca. 0.3 eV). Hence, the exploration of a new PCS mechanism to minimize the energy loss is a high-priority subject to realize efficient solar energy conversion. Interfacial charge-transfer transitions (ICTTs) enable direct PCS at heterogeneous interfaces without energy loss, in principle. Recently, several progresses have been reported for ICTT at organic-inorganic semiconductor interfaces by our group. First of all, new organic-metal oxide complexes have been developed with various organic and metal-oxide semiconductors for ICTT. Through the vigorous material development and fundamental research of ICTT, we successfully demonstrated efficient photovoltaic conversion due to ICTT for the first time. In addition, we revealed that the efficient photoelectric conversion results from the suppression of charge recombination, providing a theoretical guiding principle to control the charge recombination rate in the ICTT system. These results open up a way to the development of ICTT-based photovoltaic cells. Moreover, we showed the important role of ICTT in the reported efficient dye-sensitized solar cells (DSSCs) with carboxy-anchor dyes, particularly, in the solar energy absorption in the near IR region. This result indicates that the combination of dye sensitization and ICTT would lead to the further enhancement of the power conversion efficiency of DSSC. In this feature article, we review the recent progresses of ICTT and its application in solar cells. Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Figure 1

Other

Jump to: Research, Review

19 pages, 3612 KiB

Open AccessPerspective

Copper Coordination Complexes for Energy-Relevant Applications

by Iacopo Benesperi, Reena Singh and Marina Freitag

Energies 2020, 13(9), 2198; https://doi.org/10.3390/en13092198 - 02 May 2020

Cited by 21 | Viewed by 5860

Abstract

Copper coordination complexes have emerged as a group of transition metal complexes that play important roles in solar energy conversion, utilization and storage, and have the potential to replace the quintessential commonly used transition metals, like Co, Pt, Ir and Ru as light [...] Read more.

Copper coordination complexes have emerged as a group of transition metal complexes that play important roles in solar energy conversion, utilization and storage, and have the potential to replace the quintessential commonly used transition metals, like Co, Pt, Ir and Ru as light sensitizers, redox mediators, electron donors and catalytic centers. The applications of copper coordination compounds in chemistry and energy related technologies are many and demonstrate their rightful place as sustainable, low toxicity and Earth-abundant alternative materials. In this perspective we show the most recent impact made by copper coordination complexes in dye-sensitized solar cells and other energy relevant applications. Full article

(This article belongs to the Special Issue Advanced Dye-Sensitized Solar Cells)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Advanced Dye-Sensitized Solar Cells

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (10 papers)

Research

Review

Other

Further Information

Guidelines

MDPI Initiatives

Follow MDPI