Flexible quantum dot sensitized solar cell by electrophoretic deposition of CdSe quantum dots on ZnO nanorods

We report on a flexible quantum dot-sensitized solar cell (QDSSC) based on ZnO nanorods with a length of 2 μm. Due to the good coverage of CdSe QDs on ZnO by the electrophoretic deposition method, a maximum power conversion efficiency of ～1% is achieved for the flexible QDSSC.     

A quantum dot sensitized solar cell based on vertically aligned carbon nanotube templated ZnO arrays

We report on a quantum dot sensitized solar cell (QDSSC) based on ZnO nanorod coated vertically aligned carbon nanotubes (VACNTs). Electrochemical impedance spectroscopy shows that the electron lifetime for the device based on VACNT/ZnO/CdSe is longer than that for a device based on ZnO/CdSe, indicating that the charge recombination at the interface is reduced by the presence of the VACNTs. Due to the increased surface area and longer electron lifetime, a power conversion efficiency of 1.46% is achieved for the VACNT/ZnO/CdSe devices under an illumination of one Sun (AM 1.5G, 100 mW/cm²).     

Graphene quantum dots assisted photovoltage and efficiency enhancement in CdSe quantum dot sensitized solar cells

CdSe quantum dot sensitized solar cells(QDSCs) modified with graphene quantum dots(GQDs) have been successfully achieved in this work for the first time. Satisfactorily, the optimized photovoltage(Voc) of the modified QDSCs was approximately 0.04 V higher than that of plain CdSe QDSCs, consequently improving the photovoltaic performance of the resulting QDSCs. Served as a novel coating on the CdSe QD sensitized photoanode, GQDs played a vital role in improving Vocdue to the suppressed charge recombination which has been confirmed by electron impedance spectroscopy as well as transient photovoltage decay measurements. Moreover, different adsorption sequences, concentration and deposition time of GQDs have also been systematically investigated to boost the power conversion efficiency(PCE) of CdSe QDSCs. After the coating of CdSe with GQDs, the resulting champion CdSe QDSCs exhibited an improved PCE of 6.59% under AM 1.5G full one sun illumination.     

Titanylphthalocyanine as hole transporting material for perovskite solar cells

Titanylphthalocyanine(TiOPc) as hole transporting material(HTM) was successfully synthesized by a simple process with low cost. Perovskite solar cells using the TiOPc as HTM were fabricated and characterized. TiOPc as HTM plays an important role in increasing the power conversion efficiency(PCE) by minimizing recombination losses at the perovskite/Au interface because TiOPc as HTM can extract photogenerated holes from the perovskite and then transport quickly these charges to the back metal electrode. In the research, the β-TiOPc gives a higher PCE than α-TiOPc for the devices due to sufficient transfer dynamics. The β-TiOPc was applied in perovskite solar cells without dopping to afford an impressive PCE of 5.05% under AM 1.5G illumination at the thickness of 40 nm which is competitive with spiro-OMe TAD at the same condition. The present work suggests a guideline for optimizing the photovoltaic properties of perovskite solar cells using the TiOPc as the HTM.     

Facile solution-processed molybdenum oxide as hole transporting material for efficient organic solar cell

The large energy barrier in hole extraction still remains a great challenge in developing hole transporting layer (HTL) materials for organic solar cells (OSCs).Thus,solution-processed HTL materials with excellent hole collection ability and good compatibility with large-area processing technique are strongly desired for OSCs.Herein,we developed a cost-effective and solution-processed MoO₃ HTL for efficient OSCs.By adding a small amount of glucose as reducing reagent into the ammonium...     

Unpredicted electron injection in CdS/CdSe quantum dot sensitized ZrO2 solar cells

A quantum dot sensitized solar cell based on a porous ZrO(2) film, sensitized with CdSe quantum dots using CdS as an intermediate layer is presented. We observe electron injection from photo-excited quantum dots into the ZrO(2), which is unexpected due to the much higher conduction band edge (closer to the vacuum level) of bulk ZrO(2) compared to TiO(2).     

Low-cost solid-state dye-sensitized solar cell based on ZnO with CuSCN as a hole transport material using simple solution chemistry

Journal of Solid State Electrochemistry - Here, we report the deposition of CuSCN as a p-type hole transport material (HTM) using simple and inexpensive chemical route viz. successive ionic layer...     

Incorporation of graphene in quantum dot sensitized solar cells based on ZnO nanorods

We demonstrate a novel architecture of solar cell by incorporating graphene thin film in a quantum dot sensitized solar cell. Quantum dot sensitized nanorods with a graphene layer exhibited a 54.7% improvement comparing a quantum dot sensitized ZnO nanorods without graphene layer. A fill factor as high as ～62% was also obtained.     

PbS quantum dot sensitized anatase TiO2 nanocorals for quantum dot-sensitized solar cell applications

Lead sulphide (PbS) quantum dot (QD) sensitized anatase TiO(2) nanocorals (TNC) were synthesized by SILAR and hydrothermal techniques. The TNC, PbS and PbS-TNC samples were characterized by optical absorption, XRD, FT-IR, FESEM and XPS. The results show that PbS QDs are coated on the TNCs, the optical absorption is found to be enhanced and the band edge is shifted to ~693 nm as compared with plain TNCs at 340 nm. The PbS-TNC sample exhibits an improved photoelectrochemical performance with a maximum short circuit current (J(sc)) of 3.84 mA cm(-2). The photocurrent density was found to be enhanced 2 fold, as compared with those of the bare PbS photoelectrode. The total power conversion efficiency of the PbS-TNC electrodes is 1.23%.     

Directly assembled CdSe quantum dots on TiO2 in aqueous solution by adjusting pH value for quantum dot sensitized solar cells

We report an improved quantum dot sensitized solar cell (QDSSC) by loading mercaptopropionic acid (MPA)-capped CdSe QDs on TiO₂ film in aqueous solution. Under suitable pH value, a power conversion efficiency of 1.19% and an incident photon to current conversion efficiency of 26% for the QDSSC were obtained at AM1.5G irradiation. The improved performance of QDSSC is attributed to the large loading and good coverage of QDs on TiO₂ film with optimal pH value.     

P3HT as hole transport material and assistant light absorber in CdS quantum dots-sensitized solid-state solar cells

Regioregular poly(3-hexylthiophene) (P3HT) was employed as a hole transport material and assistant light absorber for the fabrication of a CdS quantum dot-sensitized solid-state solar cell, by which a power-conversion efficiency of 1.42% was achieved under an AM1.5 G (100 mW cm(-2)) condition.     

SnSe2 quantum dot sensitized solar cells prepared employing molecular metal chalcogenide as precursors

A kind of molecular metal chalcogenide, (N(2)H(4))(3)(N(2)H(5))(4)Sn(2)Se(6) complex, was synthesized in the hydrazine solution and employed as the precursors for SnSe(2) deposition on TiO(2) nanocrystalline porous films. A power conversion efficiency of 0.12% under AM 1.5, 1 sun was obtained for the SnSe(2) sensitized TiO(2) solar cells.     

Easily manufactured TiO2 hollow fibers for quantum dot sensitized solar cells

TiO(2) hollow fibers with high surface area were manufactured by a simple synthesis method, using natural cellulose fibers as template. The effective light scattering properties of the hollow fibers, originating from their micron size, were observed by diffuse reflectance spectroscopy. In spite of the micrometric length of the TiO(2) hollow fibers, the walls were highly porous and high surface area (78.2 m(2) g(-1)) was obtained by the BET method. TiO(2) hollow fibers alone and mixed with other TiO(2) pastes were sensitized with CdSe quantum dots (QDs) by Successive Ionic Layer Adsorption and Reaction (SILAR) and integrated as a photoanode in quantum dot sensitized solar cells (QDSCs). High power conversion efficiency was obtained, 3.24% (V(oc) = 503 mV, J(sc) = 11.92 mA cm(-2), FF = 0.54), and a clear correspondence of the cell performance with the photoanode structure was observed. The unique properties of these fibers: high surface area, effective light scattering, hollow structure to facile electrolyte diffusion and the rather high efficiencies obtained here suggest that hollow fibers can be introduced as promising nanostructures to make highly efficient quantum dot sensitized solar cells.     

Mn-doped quantum dot sensitized solar cells: a strategy to boost efficiency over 5%

To make Quantum Dot Sensitized Solar Cells (QDSC) competitive, it is necessary to achieve power conversion efficiencies comparable to other emerging solar cell technologies. By employing Mn(2+) doping of CdS, we have now succeeded in significantly improving QDSC performance. QDSC constructed with Mn-doped-CdS/CdSe deposited on mesoscopic TiO(2) film as photoanode, Cu(2)S/Graphene Oxide composite electrode, and sulfide/polysulfide electrolyte deliver power conversion efficiency of 5.4%.     

Synthesis of ZnO nanorods and their application in quantum dot sensitized solar cells

ZnO nanorod thin films of different thicknesses and CdS quantum dots have been prepared by chemical method. X-ray diffraction pattern reveals that the CdS quantum dot and ZnO nanorods are of hexagonal structure. Field emission scanning electron microscope images show that the diameter of hexagonal shaped ZnO nanorods ranges from 110 to 200 nm and the length of the nanorod vary from 1.3 to 4.7 μm. CdS quantum dots with average size of 4 nm have been deposited onto ZnO nanorod surface using successive ionic layer adsorption and reaction method and the assembly of CdS quantum dot with ZnO nanorod has been used as photo-electrode in quantum dot sensitized solar cells. The efficiency of the fabricated CdS quantum dot-sensitized ZnO nanorod-based solar cell is 1.10 % and is the best efficiency reported so far for this type of solar cells.     

CdS and CdSe quantum dots subsectionally sensitized solar cells using a novel double-layer ZnO nanorod arrays

We report a novel approach for synthesizing CdS and CdSe quantum dots subsectionally sensitized double-layer ZnO nanorods for solar cells, which are comprised of CdS QDs-sensitized bottom-layer ZnO NRs and CdSe QDs-sensitized top-layer ZnO NRs. X-ray diffraction study and scanning electron microscopy analysis indicate that the solar cells of subsectionally sensitized double-layer ZnO NRs, which are the hexagonal wurtzite crystal structure, have been successfully achieved. The novel structure enlarged the range of absorbed light and enhanced the absorption intensity of light. The I-V characteristics show that the double-layer structure improved both the current density (J_sc) and fill factor (FF) by 50%, respectively, and power conversion efficiency (η) was increased to twice in comparison with the CdS QDs-sensitized structure.     

Planar core based starburst triphenylamine molecules as hole transporting materials for high-performance perovskite solar cells

<正>Starburst triphenylamine molecules are generally used as hole transporting materials (HTMs) for optoelectronic devices like solar cells, light emitting diode and field effect transistors [1]. The use of starburst triphenylamine molecules like spiro-OMeTAD HTM initiated the construction of solid state perovskite solar cells (PSCs)[2,3]. Currently, based on triphenylamine HTMs, the highest power conversion efficiency (PCE) of PSCs is up to 22.1%[4]. Nowadays, spiro-     

Metal chalcogenide complex-mediated fabrication of Cu2S film as counter electrode in quantum dot sensitized solar cells

Cu2S film onto FTO glass substrate was obtained to function as counter electrode for polysulfide redox reactions in CdS/CdSe co-sensitized solar cells by sintering after spraying a metal chalcogenide complex, N4H9Cu7S4 solution. Relative to Pt counter electrode, the Cu2S counter electrode provides greater electrocatalytic activity and lower charge transfer resistance. The prepared Cu2S counter electrode represented nanoflower-like porous film which was composed of Cu2S nanosheets on FTO and had a higher surface area and lower sheet resistance than that of sulfided brass Cu2S counter electrode. An energy conversion efficiency of 3.62% was achieved using the metal chalcogenide complex-mediated fabricated Cu2S counter electrode for CdS/CdSe co-sensitized solar cells under 1 sun, AM 1.5 illumination.     

Spectral broadening in quantum dots-sensitized photoelectrochemical solar cells based on CdSe and Mg-doped CdSe nanocrystals

In order to absorb a broad spectrum in visible region, a co-sensitized TiO₂ electrode was prepared by CdSe and Mg-doped CdSe quantum dots (Q dots). The power conversion efficiency of the co-sensitized Q dots photoelectrochemical solar cells (PECs) showed 1.03% under air mass 1.5 condition (I = 100 mW/cm²), which is higher than that of individual Q dots-sensitized PECs. The incident-photon-to-current conversion efficiency of the co-sensitized PECs showed absorption peaks at 541 and 578 nm corresponding to the two Q dots and displayed a broad spectral response over the entire visible spectrum in the 500–600 nm wavelength domains.     

A novel phenoxazine-based hole transport material for efficient perovskite solar cell

Based on the previous research work in our laboratory, we have designed and synthesized a small-molecule,hole transport material(HTM) POZ6-2 using phenoxazine(POZ) as central unit and dicyanovinyl units as electron-withdrawing terminal groups. Through the introduction of a 2-ethyl-hexyl bulky chain into the POZ core unit, POZ6-2 exhibits good solubility in organic solvents. In addition, POZ6-2 possesses appropriate energy levels in combination with a high hole mobility and conductivity in its pristine form. Therefore, it can readily be used as a dopant-free HTM in perovskite solar cells(PSCs) and a conversion efficiency of 10.3% was obtained. The conductivity of the POZ6-2 layer can be markedly enhanced via doping in combination with typical additives, such as 4-tert-butylpyridine(TBP) and lithium bis(trifluoromethanesulfonyl) imide(Li TFSI).Correspondingly, the efficiency of the PSCs was further improved to 12.3% using doping strategies. Under the same conditions, reference devices based on the well-known HTM Spiro-OMe TAD show an efficiency of 12.8%.