Semiconductor-sensitized Solar Cells Research Articles

Temperature effects on Cadmium Selenide semiconductor-sensitized solar cells with SnO2 deposition as electron transport layer

Temperature effects on Cadmium Selenide semiconductor-sensitized solar cells with SnO2 deposition as electron transport layer

Photoelectric properties of the layered raspberry sandwich amorphous ZnCo2S4@MnCo2S4/CP composite counter electrode in semiconductor-sensitized solar cells.

Multistage amorphous materials have promising applications in the catalytic performance of dye-sensitized solar cells (DSSCs). Herein, an amorphous sheet-raspberry sandwich-like ZnCo2S4@MnCo2S4/CP composite material was rationally designed and developed as a counter electrode (CE) for DSSCs by applying a three-step hydrothermal method. The first development of the amorphous composites as CEs resulted in lower charge transfer resistance at the CE/electrolyte interface and improved the fill factor and short-circuit current density. The excellent catalytic performance is mainly attributed to the large number of unsaturated coordination sites generated by the undirected structure of the lamellar-raspberry intercalated amorphous material, the smooth ion transport interface with a self-built corrosion-resistant layer, coupled with the dual catalytic performance of the Zn, Co, and Mn composites, and the good electrical conductivity of the C substrate. When ZnCo2S4@MnCo2S4/CP was used as the CE on a Ti substrate, the photoelectric conversion efficiency was as high as 11.68% (Voc = 0.821, Jsc = 20.14 mA cm-2, and FF = 0.71) under 100 mW cm-2 light illumination. This paper provides a design idea for amorphous materials in terms of catalytic performance and a method for developing alternatives to Pt electrodes.

Enhancement of opto-electrical properties in Co doped CdS–TiO2 nanocomposite thin film as photoanode for Semiconductor Sensitized Solar Cells (SSSCs)

Cobalt doped CdS–TiO 2 nanocomposite thin films were coated on glass substrates by bottom up approaching methods. ZnS nanolayer over cobalt doped CdS–TiO 2 films act as a protective layer of CdS nanocrystal which enhances the photo stability. The structural, optical, electrical and surface morphological properties of ZnS-cobalt CdS–TiO 2 composite thin film were systematically evaluated. Structural analysis indicates that Co 2+ ions have been successfully incorporated in CdS site. The doping of cobalt in ZnS–CdS–TiO 2 film gives rise to an increase in the lattice parameter while the band gap decreased with increasing cobalt concentration. The bandgap of doped film decreases indicating the easy way of electron transfer from valence band to conduction band of CdS and TiO 2 . Surface morphological studies shows the diffusion of cobalt doped CdS nanoparticles into TiO 2 nanoporous structure of the composite film . The emission peaks in photoluminescence spectrum of ZnS-cobalt CdS–TiO 2 film proved the clear interaction of cobalt dopant with CdS nanocrystals. An enhancement in conductivity was observed due to incorporation of cobalt in CdS site and the resistance value (∼47%) was significantly decreased for cobalt doped CdS under illumination condition. Electrical analysis proved that the doped film is preferred as conductive electrode in solar cells than undoped film. • Cobalt doped CdS–TiO 2 composite thin films were synthesized by simple wet chemical method. • Interlocked CdS nanocrystals observed in SEM analysis, facilitate easy penetration into TiO 2 nanoporous structure of the composite film. • The doped film exhibit shifting of absorption edge towards longer wavelength (red shift), indicates decreased optical band gap. • The doped film shows superior electrical performance due to decreased resistance, preferred as conductive electrode in solar cells.

Simple chemical route synthesized TiO2/Ag2S heterostructure towards efficient semiconductor sensitized solar cells

The efficient and inexpensive semiconductor sensitized solar cell (SSSC) device is fabricated based on TiO2/Ag2S photoanode, synthesized by chemically grown Ag2S nanoparticles over porous TiO2 at room temperature. The structural, optical, surface morphological and electrochemical performances of as deposited TiO2/Ag2S photoanode are systematically studied. The result designated that the tiny Ag2S nanoparticles are uniformly decorated on porous TiO2 thin film and efficiently extended their photo response in visible region of solar spectrum. Furthermore the paper explored the potential of Ag2S nanoparticles as a sensitizer in SSSC by constructing sandwich type device structure. The electrochemical and photovoltaic performance of the proposed architecture clearly reveals the charge transportation as well as device grade performance is significantly influenced by number of deposition cycles. The maximum photo conversion efficiency of 1.3% is achieved under illumination of simulated sunlight.

(Invited) Mechanism of a Sensitized Thermal Cell

Efficient and low-cost thermal energy-harvesting systems are crucial to solve the global energy problem. A new energy conversion system for the generation of electric power directly from heat energy is described herein. The device is a sensitized thermal cell (STC) based on a dye-sensitized solar cell. In the established system, thermally-excited electrons in a semiconductor were utilized instead of photon-excited electrons in a dye. Consequently, the STC generated electricity by “placing” or “burying” the cell in the heat source.To prove the concept, first, we examined the redox ability of thermally excited electrons (Mater. Horiz., 2017, 4, 649–656.). Next, we demonstrated that the semiconductor-sensitized solar cell can generate electric power by thermally excitation (ACS Applied Energy Materials, 2019, 2, 13–18.; J. Phys. Chem. C, 123, 2019, 12135-12141.). Lastly, we performed the long-time power generation at 80 degree using STC and observed the end; and surprisingly found that the battery characteristics were restored after discharging by placing or burying the battery in a heat source ( J. Mater. Chem. A, 2019, 7, 18249-18256.). Additinally, we show that the open circuit voltage of STC has the Fermi level dependnce of the semiconductor electrode (Chem. Lett. in press). In the presentation, these recent results were summarized and the difference between photo excitation and thermally excitation will be discussed..

Comparison of Eosin yellowish dye–sensitized and CdS-sensitized TiO2 nanomaterial–based solid-state solar cells

In the present work, Eosin yellowish (EY) dye–sensitized and CdS-sensitized TiO2 photoanodes prepared by doctor blade technique, for dye (DSSC)- and semiconductor-sensitized solar cell (SSSC) by engaging different forms of solid-state electrolyte. To begin with, the TiO2 and CdS/TiO2 nanomaterials are synthesized by the solvothermal method and the changing of physical properties is examined from structural, optical, morphological, and chemical composition measurements. The formation of anatase tetragonal phase TiO2 and hexagonal phase CdS are investigated from XRD. UV-vis and photoluminescence studies expose that the nanomaterials loaded with different amounts of CdS on TiO2 extend the absorption wavelength region from ultraviolet to visible. The photovoltaic performances of pure and CdS-added TiO2 nanoparticle have studied by current-voltage measurement and impedance spectral response. We have achieved the highest solar conversion efficiency of 2.89% with the aid of the CdS-sensitized TiO2 photoanode. CdS-sensitized TiO2 photoanode shows good stability as inferred from transient photocurrent and photovoltage measurements. Overall investigation describes that the inclusion of CdS into the TiO2 photoanodes gradually increase efficiency and stability.

Employing Successive Ionic Layer Adsorption and Reaction (SILAR) Method on the Fabrication of Cu3BiS3-Semiconductor-Sensitized Solar Cells

Successive ionic layer adsorption and reaction (SILAR) method is a modified version of chemical bath deposition (CDB) that serves as a low-cost and convenient on the production of ternary metal chalcogenides. This research reported the utilization of SILAR method on the fabrication of Cu3BiS3 semiconductor-sensitized solar cells. The concentration of bismuth and copper precursor were varied, namely 0.03 M and 0.1 M, whereas the precursor of sulfide was varied in the concentration of 0.02 M and 0.05 M. The variation of SILAR cycles was employed to investigate the most appropriate cycle numbers in producing Cu3BiS3, in particular 3-9 cycles, 5-15 cycles, and 6-6 cycle with the immersing time of 20 s for each. The results show that there were only two suitable peaks appeared for 3-9 cycles and 6-6 cycles, while 5-15 cycles provide the more preferable XRD patterns with the power conversion efficiency of 0.02% (Jsc of 1.75 mA/cm2; Voc of 0.04 V; FF of 29.65%). It can be said that SILAR method with higher number of cycles can be employed to fabricate Cu3BiS3; however, smaller PCE came from inappropriate structure alignment between Cu3BiS3 and metal oxide layer.

ZnS passivated PbSe sensitized TiO2 nanorod arrays to suppress photocorrosion in photoelectrochemical solar cells

Harmonized effect of TiO2 and PbSe on the photoconversion efficiency of semiconductor sensitized solar cells (SSSCs) is studied. Rutile TiO2 nanorods (NRs) grown by hydrothermal method provides remarkably high surface area, superior injection and charge collection efficiency. TiO2 NRs are sensitized by PbSe using chemical bath deposition (CBD) and ZnS layer where ZnS acts as a surface passivation layer grown by successive ionic layer adsorption and reaction (SILAR) method. Photoelectrodes made up of sensitization can absorb the ultraviolet (UV) as well as the visible region of the solar spectrum efficiently. Synthesized photoelectrodes were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), optical and solar cell performances. FESEM images of the photoelectrodes illustrate uniform coverage of PbSe over TiO2 NRs increases with increasing deposition time. The ZnS layer avoids the recombination of charge carriers. The photoelectrochemical (PEC) study is carried out using an optimized device structure i.e. Glass/FTO/TiO2/PbSe/ZnS/Polysulphide/Pt/FTO/Glass. Under AM 1.5 G illumination, the T18-PbSe2-ZnS3 photoelectrode shows 0.34% photoconversion efficiency demonstrate lead chalcogenides have potential applications in solar cells.

CdS nanosheet-sensitized solar cells based on SnO2/MgO composite films

We report CdS nanosheet-sensitized solar cells based on SnO2/MgO composite films for the first time. Though, TiO2 and SnO2 have been used for semiconductor-sensitized solar cells (SSCs), composite films based on SnO2, have not yet been used to fabricate SSCs. In this work, CdS nanosheets were used to sensitize the SnO2/MgO-based solar cells. A thin film of CdS nanostructures was deposited on the mesoporous, SnO2/MgO film by chemical bath deposition (CBD) method at different bath temperatures. A ZnS layer was also deposited on the as-prepared CdS nanosheets, which acts as a capping layer to passivate the surface states of CdS nanosheets as well as a barrier to suppress the recombination of photo-generated electrons with the electrolyte. A power conversion efficiency of 1.33% could be obtained in this regard which is comparable with those obtained by other systems sensitized by CdS.

Synthesis of crystalline umangite phase of copper selenide (Cu3Se2) for TiO2 photoanode-based solar cell application

This study deals with the sensitization of the porous titanium oxide (TiO2) films deposited on fluorine doped tin oxide with copper selenide (Cu3Se2). The sensitization was achieved for three different sensitization times employing chemical solution deposition with copper sulfate and sodium selenosulphate as precursors for copper and selenium ions, respectively. X-ray diffraction analysis confirms the tetragonal crystal phase of prepared Cu3Se2 film on glass substrate and deposition of Cu3Se2 on TiO2 film. Optical absorption spectra showed that deposition of Cu3Se2 film helps to enhance the photo-response of the TiO2 film. The Raman spectra analysis shows existence of vibration mode of Cu-Se covalent bond with lattice vibration modes of anatase phase of titanium oxide. Semiconductor-sensitized solar cell is fabricated for energy harvesting purpose with Cu3Se2-sensitized TiO2 photoanode, polysulphide electrolyte, and α-MoO3 carbon composite counter electrode. The working mechanism and energy level diagram of Cu3Se2/TiO2 system are discussed.

Synthesis and deposition of nanostructured SnS for semiconductor-sensitized solar cell

Structural, electrical, and optical properties of SnS nanoparticles and films deposited by ultrasound-assisted chemical bath were studied. The SnS was synthesized using tin chloride and thioacetamide as a tin and sulfur source, respectively. The obtained powder and films were characterized by using X-ray diffraction, field emission scanning electron microscopy, scanning electron microscopy, energy dispersive spectroscopy, particle size distribution analysis, and ultraviolet-visible spectroscopy. The synthesized SnS was crystalline in nature with an orthorhombic structure. To study the solar cell performance, the titanium dioxide photoanode was deposited on to the fluorine-doped tin oxide-coated glass (FTO) substrate. Further, the SnS was deposited on especially fabricated titanium dioxide film and the cell was made by using platinum-coated FTO as a counter electrode and a drop of polysulfide as an electrolyte.

Strain-Induced Type II Band Alignment Control in CdSe Nanoplatelet/ZnS-Sensitized Solar Cells

Colloidal CdSe nanoplatelets (NPLs) deposited on TiO2 and overcoated by ZnS were explored as light absorbers in semiconductor-sensitized solar cells (SSSCs). Significant red shifts of both absorption and steady-state photoluminescence (PL) along with rapid PL quenching suggest a type II band alignment at the interface of the CdSe NPL and the ZnS barrier layer grown on the NPL layer, as confirmed by energy band measurements. The considerable red shift leads to enhanced spectral absorption coverage. Cell characterization shows an increased open-circuit voltage of 664 mV using a polysulfide electrolyte, which can be attributed to a photoinduced dipole effect created by the spatial charge separation across the nanoplatelet sensitizers. The observed short-circuit current density of 11.14 mA cm–2 approaches the maximal theoretical current density for this choice of absorber, yielding an internal quantum efficiency of close to 100%, a clear signature of excellent charge transport and collection yields. With thei...

Phenoxazine Derivative Operates as an Efficient Surface-Grafted Molecular Relay to Enhance the Performance and Stability of CdS- and CdSe-Sensitized TiO2 Solar Cells.

We report on a new phenoxazine derivative, 10-butyl-phenoxazine-3-carboxylic acid (BPCA), that we designed to operate as a molecular relay in semiconductor-sensitized solar cells (SSCs). After BPCA surface modification and in the presence of a cobalt-bipyridyl complex acting as a redox mediator, both TiO2 /CdS/BPCA and TiO2 /CdSe/BPCA SSCs exhibit enhanced photovoltaic performance and stability. In particular, the power conversion efficiencies of CdS and CdSe-based solar cells are improved by 90 % and 57 %, respectively. Furthermore, after 300 s the JSC of TiO2 /CdS/BPCA SSCs is stabilized at 30 % of its initial value, while in the same time CdS-based devices retain only 1 % of their initial JSC . The origin of the improvement arises from the excellent electron-donating property of BPCA and its role as a powerful molecular relay in non-polysulfide based SSCs.

Synthesis, characterization, and photovoltaic properties of TiO2/CdTe core-shell heterostructure for semiconductor-sensitized solar cells (SSSCs)

The present work represents successful synthesis of CdTe-sensitized TiO2 nanoarray thin films by two simple chemical routes. Here, we report the sensitization of TiO2 nanoarrays with CdTe nanoparticles through the electrodeposition technique at ambient condition. The electrodeposition of 30 min leads to the formation of shell of CdTe nanoparticles over TiO2 nanoarrays. This core-shell formation structure was further confirmed by TEM and HR-TEM analysis. Optical absorption and photoelectrochemical study revealed that the TiO2/CdTe core-shell heterostructure extend the absorption edge of titania in the visible region of solar spectrum; it also facilitates the efficient charge transport and reduces the recombination losses. The maximum photoconversion efficiency of 0.32% is obtained for TiO2/CdTe core-shell semiconductor-sensitized solar cells (SSSCs).

Sodium antimony sulfide (NaSbS2): Turning an unexpected impurity into a promising, environmentally friendly novel solar absorber material

We present a novel absorber material—NaSbS2—for solar cells. NaSbS2 is formed as an unexpected byproduct in the chemical synthesis of Sb2S3. However, NaSbS2 has many attractive features for a solar material. Here single phase NaSbS2 nanoparticles were synthesized through solution processing. NaSbS2 semiconductor-sensitized solar cells were demonstrated for the first time. The best cell yielded Jsc = 10.76 mA/cm2, Voc = 0.44 V, FF = 48.6%, and efficiency η = 2.30% under 1 sun. At the reduced 0.1 sun, the η increased to 3.18%—a respectable η for a new solar material.

Ag3SbS3 Liquid-Junction Semiconductor-Sensitized Solar Cells

We present a new ternary semiconductor absorber material – Ag3SbS3 – for solar cells. Ag3SbS3 nanoparticles were grown on mesoporous TiO2 electrodes using a two-stage successive ionic layer adsorption reaction process. Post annealing transformed the double-layered structure into the Ag3SbS3 phase. The energy gap of the synthesized Ag3SbS3 nanoparticles is estimated to be ∼1.5–1.7 eV. Liquid-junction semiconductor-sensitized solar cells were fabricated from the synthesized nanoparticles using a polysulfide electrolyte. The best cell yielded a short-circuit current density Jsc of 11.47 mA/cm2, an open-circuit voltage Voc of 0.33 V, a fill factor FF of 38.92%, and a power conversion efficiency η of 1.47% under 1 sun. The external quantum efficiency (EQE) spectrum covered the spectral range of 300–850 nm with a maximal EQE = 80% at λ = 500 nm. At the reduced light intensity of 13% sun, the η increased to 2.18% with Jsc = 2.46 mA/cm2 (which could be normalized to 18.9 mA/cm2). The respectable photovoltaic performance indicates that Ag3SbS3 could be a potential solar absorber material.

Influence of Depletion Width on Charge Transport and Interfacial Recombination in Extremely Thin Absorber Solar Cells

Understanding the dynamics of charge transport and recombination and their dependence on physical and electrochemical length scales in extremely thin absorber (ETA) solar cells is vital to cell design. We used J-V characterization, transient photocurrent/photovoltage, and electrochemical impedance spectroscopy to study electron transport and interfacial recombination in ETA cells. ETA cells were composed of ZnO nanowires coated with CdSe absorbers with thicknesses of 10–40 nm, with polysulfide electrolyte. The relative size of the absorber thickness and the bias-dependent depletion width was found to be a controlling factor in both transport and recombination. In thinner absorbers near short circuit, the depletion region can extend radially into the nanowire, inhibiting interfacial recombination. However, depleting the periphery of the nanowire reduces the cross sectional area for charge transport, resulting in longer characteristic collection times. Overall, cells with thicker absorbers suffered more significant bias-dependent collection, and we conclude that slight radial penetration of the depletion region into the nanowires enhances charge collection. While depletion width is often associated with charge separation in the absorber, this work highlights the importance of considering the impact of depletion width on charge transport and interfacial recombination in the design of liquid junction, semiconductor-sensitized solar cells.

Aqueous synthesis of panchromatic luminescent CdTeSe alloyed quantum dots

Highly panchromatic luminescent CdTexSe1−x alloy quantum dots (QDs) with emissions from blue to red regions are synthesized using a one-step method in aqueous solution with 3-mercaptopropionic acid (3-MPA) as stabilizer. The structure, shape, and spectral properties of these alloy QDs are investigated. The structure of the obtained CdTexSe1−x QDs is consistent with the zinc-blende crystal structure, with a nearly spherical shape having diameter of 4–7nm. The CdTexSe1−x QDs exhibit an absorbance wavelength ranging from 460nm to 700nm, and the maximum quantum yield (QY) approaches 28% for CdTe0.5Se0.5 alloy QDs with a reflux time of 0.5h. The emission wavelength of CdTexSe1−x QDs can be continuously tuned from 500nm to 720nm by controlling the size and composition of the alloy QDs, indicating their potential use in semiconductor-sensitized solar cells.

Boosting the Performance of ZnO/CdS Core‐Shell Nanorod Array‐based Solar Cells by ZnS Surface Treatment

AbstractWith a view to enhancing the efficiency of ZnO/CdS core‐shell nanorod array‐based semiconductor sensitized solar cells (SSSCs), ZnS surface treatment is envisioned. It is achieved through a thin layer of ZnS being deposited onto ZnO/CdS film by a successive ionic layer adsorption and reaction (SILAR) technique. To ascertain the optimum thickness of ZnS and to enhance the solar cell performance, we have varied the number of SILAR cycles of ZnS deposition. The optimized film is then considered for structural, morphological, and electrochemical studies. The analysis reveals the benefits of ZnS surface treatment on ZnO/CdS core‐shell photoelectrodes in terms of an enhancement of solar cell performance of up to 1.54 % from 1.23 %.

Fast Charge Separation at Semiconductor Sensitizer–Molecular Relay Interface Leads to Significantly Enhanced Solar Cell Performance

We report on an effective strategy to improve the efficiency and stability of liquid junction semiconductor-sensitized solar cells employing cobalt bipyridyl complex-based electrolyte. With CdS-sensitized TiO2 as a model system, we demonstrate that grafting the surface of CdS with small relay molecule, 4′-(bis(4-(hexyloxy)phenyl)amino)biphenyl-4-carboxylic acid (PAPC), drastically improves the cell performance and leads to an unprecedented power conversion efficiency. Transient absorption measurement indicates the photogenerated holes in CdS could be instantaneously intercepted by the grafted PAPC molecules, which greatly facilitates the charge separation and thus stabilizes CdS. We believe such a concept could be applied to other semiconductor sensitizers, especially for those with superior light absorption, such as CdSe, CdTe, etc.