Short-circuit Photocurrent Research Articles

Theoretical design of porphyrin dyes with electron-deficit heterocycles towards near-IR light sensitization in dye-sensitized solar cells

We develop a series of porphyrin sensitizers with electron-deficit heterocycles based on the well-known YD2-o-C8 dye for application in dye-sensitized solar cells with the help of ab initio density functional theory calculations and quantum dynamics simulation based on the tight-binding extended Hückel Hamiltonian at the semiempirical level. The calculation results show that introduction of electron-deficit heterocycles into the porphyrin dyes can remarkably red-shift and broaden the Q band of the absorption spectrum and extend the coverage into near-infrared region, improving the light-harvesting ability. The key parameters influencing the photocurrent and photovoltage performance such as maximum short-circuit photocurrent (JSCmax), intramolecular charge transfer, interface electron injection, and the shift of TiO2 conduction band edge (ΔECB) are superior to YD2-o-C8 dye. Therefore, the designed sensitizers would be promising candidate for utilization in dye-sensitized solar cells.

Zn and Sr co-doped TiO2 mesoporous nanospheres as photoanodes in dye sensitized solar cell

Mesoporous TiO2 nanospheres that were co-doped with Zn and Sr were synthesized via a simple hydrothermal method. These materials were used as the photoanode in dye-sensitized solar cells (DSSCs). Field-emission electron microscopy showed that the nanospheres were monodisperse and interconnected, while transmission electron microscopy (TEM) showed that the nanospheres were composed of different nanostructures (nanotubes, diamond and sheet-like structures). Scanning TEM showed a homogeneous distribution of Sr, Ti, Zn and O throughout the nanospheres. When the Zn, Sr co-doped mesoporous TiO2 nanospheres were incorporated into DSSCs, a device efficiency of 4.6%, a short circuit photocurrent density of 8.63 mA cm−2 and an open circuit voltage 0.72 V were achieved. The efficiencies of these devices were higher than that of a comparison device (2.9%) that contained TiO2 (P25).

Novel stainless steel based, eco-friendly dye-sensitized solar cells using electrospun porous ZnO nanofibers

Herein, we report a new type of eco-friendly, cost-effective stainless steel mesh-based flexible quasi-solid dye-sensitized solar cell (DSSC) using electrospun ZnO nanofibers as the photoelectrode. The electrospun ZnO nanofibers showed enhanced surface to volume ratio due to the high porosity of the fibers composed of ZnO grains having 12–20 nm size with high interconnectivity. For DSSCs fabrication, commonly available natural dye chlorophyll was extracted from the Neem plant and used as the dye sensitizer. An overall solar cell conversion efficiency of 0.13 % was observed for the assembled DSSC with a short-circuit photocurrent, open-circuit voltage and fill factor of 28 μA, 0.321 mV and 32.77 %respectively. The present approach to develop cost-effective and eco-friendly DSSCs would open up enormous possibilities in effective harvesting of solar energy for commercial and rural area applications

Ferroelectric, Optical, and Photovoltaic Properties of Morphotropic Phase Boundary Compositions in the PbTiO3–BiFeO3–Bi(Ni1/2Ti1/2)O3 System

Ferroelectrics can exhibit the bulk photovoltaic effect (BPVE), which enables a switchable photoresponse and above-band-gap open-circuit voltages (Voc). For these systems a large remnant polarization (Pr) combined with a narrow band gap (Eg) is believed to be critical in optimizing the photovoltaic performance. Here we investigate the PbTiO3-BiFeO3-Bi(Ni1/2Ti1/2)O3 system which exhibits a large bulk Pr and a tunable narrow Eg. To optimize the ferroelectric polarization, ceramic samples were prepared in the vicinity of the ternary morphotropic phase boundary (MPB) and their photovoltaic properties were characterized over a broad range of optical wavelengths. MPB compositions with a direct optical gap ranging from 2.25 - 2.85 eV and Pr = 32 - 39 μC/cm2 show a BPVE with Voc = 6 V at room temperature and a wavelength-dependent switchable photoresponse. Under 1 sun AM1.5 G illumination the short-circuit photocurrent (jsc) increased by an order of magnitude as Eg was lowered from 2.85 eV to 2.25 eV, with ~ 0.1 ...

Enhanced photovoltaic property based on reduced leakage current and band gap in Nd-doped BiFeO3 films

Nd-doped BiFeO3 films were successfully fabricated on FTO glass substrate via sol-gel and spin-coating methods. Both the short circuit photocurrent density and the open circuit photovoltage of Nd-doped BiFeO3 film are clearly improved compared with the pristine BiFeO3 film, leading to more than 8-fold enhancement in power conversion efficiency for Bi0.9Nd0.1FeO3. The enhanced photovoltaic property benefits from reduced bandgap and leakage current after Nd-doping. The leakage current density of the Bi0.9Nd0.1FeO3 film is two orders lower than that of the pristine BiFeO3 film, which is the lowest in the reported BiFeO3 films. Nd-doped BiFeO3 film also shows the better ferroelectric and dielectric properties, which favored the practical application of BiFeO3 in multifunctional devices such as nonvolatile ferroelectric memories, novel photovoltaic devices and high frequency electrical components.

Enhancing the Performance of Si-Based Photocathodes for Solar Hydrogen Production in Alkaline Solution by Facilely Intercalating a Sandwich N-Doped Carbon Nanolayer to the Interface of Si and TiO2.

Photoelectrochemical (PEC) water splitting is a promising but immensely challenging technology for sustainable production of hydrogen. To this end, highly active, durable, and inexpensive photocathodes that operate under conditions compatible with those for photoanodes are desired. Herein, Si-based composite photocathodes were constructed by coating the front surface of Si with an N-doped carbon nanolayer and then a TiO2 protective layer, followed by decorating the electrode surface with Ni and Ni-Mo catalysts. The carbon nanolayer, denoted as CPDA, was formed directly on the Si surface by in situ self-polymerization of dopamine, followed by carbonization of the polydopamine (PDA) coating. The performance of the as-fabricated Si photocathodes with and without the CPDA layer was comparatively studied for PEC hydrogen evolution reaction (HER) inalkaline electrolytes to evaluate the effect of the sandwich CPDA layer in between the Si substrate and the TiO2 layer on the photoelectrocatalytic behaviors of Si-based electrodes. The photocathodes containing the CPDA layer demonstrated lower electron transfer resistance, higher built-in photovoltage, and larger band bending relative to the analogous electrodes without the CPDA layer. Accordingly, the short-circuit photocurrents of the Ni and Ni-Mo-decorated photocathodes with the CPDA layer were enhanced by a factor of 2.8-3.3, and their open-circuit photovoltages were enlarged by 0.14-0.22 V, compared to those of the corresponding electrodes without the CPDA layer in 1 M KOH under simulated 1 sun illumination. Moreover, the photocathodes with the CPDA layer also exhibited an improved stability for PEC HER in alkaline solutions, with a faradaic efficiency of 90-97% in the initial hour.

Enhanced open-circuit photovoltage and charge collection realized in pearl-like NiO/CuO composite nanowires based p-type dye sensitized solar cells

Low open-circuit photovoltage and poor hole transfer character of semiconductors have limited the development of p-type dye-sensitized solar cells (p-DSSCs) owing to the minor energy-gap between the conduction band of NiO and the Nernstian potential of the I3−/I− electrolyte, as well as the low intrinsic hole-conductivity of NiO semiconductor. Hereby, a novel NiO/CuO nanocomposite was well-designed and successfully fabricated as photocathode material of p-DSSCs. Combined with Co2+/Co3+ electrolyte, the devices showed noticeable enhancement of both open-circuit photovoltage and short-circuit photocurrent. Compared to NiO, a deeper valence-band of NiO/CuO resulted in a 140 mV improvement of photovoltage of p-DSSCs. Electrochemical impedance spectroscopy indiates an improved hole transport of NiO/CuO nanocomposite due to modified effect by CuO. Charge recombinations are also suppressed to achieve increased charge collection efficiencies and improved photoelectrochemical performance.

Enhancement of photoelectric conversion efficiency with sulfur-doped g-C3N4/TiO2 nanoparticles composites in dye-sensitized solar cells

S-doped g-C3N4/TiO2 nanoparticle composites (TCNS) were generated by successfully calcinating a compound of thiourea and TiO2 at 550 °C; these composites serve as a promising photoanode material for dye-sensitized solar cells (DSSCs) with improved efficiency. TEM, HRTEM, XRD, UV–Vis and FTIR results showed that the surfaces of TiO2 nanoparticles were coated with a thin layer of sulfur-doped g-C3N4. The corresponding photoelectrochemical properties of the fabricated DSSCs were also studied. The DSSCs based on the TCNS photoelectrode shows a ratio of 4.87% in converting light into electricity, a short-circuit photocurrent of 10.41 mA cm−2, and an open-circuit voltage of 0.65 V, qualities which were well above those of DSSCs based on un-doped TCNS. The significant enhancement in DSSC performance is mainly due to the suppression of the recombination of electron–hole (e−–h+) pairs, suppression which also leads to an increase in open-circuit photovoltage, as well as photocurrent density under short circuit by the layer of sulfur-doped g-C3N4. Additionally, electrochemical impedance spectroscopy analysis proved that the electron transfer resistance is considerably reduced, and this reduction increases the power conversion efficiency.

NATURAL HIBISCUS DYE AND SYNTHETIC ORGANIC EOSIN Y DYE SENSITIZED SOLAR CELLS USING TITANIUM DIOXIDE NANOPARTICLES PHOTO ANODE: COMPARATIVE STUDY

Titanium dioxide (TiO[Formula: see text] nanoparticles have been synthesized by the cost effective Sol–Gel technique. Characteristics of TiO2nanoparticles were investigated by X-ray diffraction and Fourier Transform Infrared spectroscopy. The Eosin Y dye and dye extracted from Hibiscus tea have been successfully used in fabrication of the dye sensitized solar cell. The photovoltaic performance of the dye sensitized solar cell indicates that the short circuit photo current, open circuit voltage and efficiency of the DSSC using Eosin Y dye is 10 times more compared to the DSSC using the Hibiscus dye.

Characterizations of 2-(pyranoquinolin-4-yl) malononitrile/p-silicon heterojunction

Thin film of 2-(pyranoquinolin-4-yl) malononitrile, PQM, was deposited on p-Si to fabricate a heterojunction of PQM/Si. Current–voltage characteristics for PQM/p-Si were investigated as a function of temperature. The diode ideality factor was calculated at different temperatures. The mechanisms for current transport in forward and reverse bias were deduced. At low voltage, the thermionic emission is the predominant mechanism of charge transport in PQM/p-Si. While ohmic conduction was observed at the higher voltage in PQM/p-Si. The photovoltaic performance for PQM/p-Si under illumination was studied and the parameters of short circuit photocurrent ISC, open-circuit photovoltage Voc and fill factor FF were calculated.

The preparation of dye sensitized solar cells using natural dyes extracted from Phytolacca icosandra and Phyllanthus reticulatus with ZnO as photoanode

Dye sensitized solar cells are promising class of photovoltaic cells with the capability of generating green energy at low production cost since no expensive equipment is required in their fabrication. Zinc oxide (ZnO) nanorods were synthesized by hydrothermal method and their performance as photoanodes in dye sensitized solar cells (DSSCs) with dye extracts from fruits of Phytolacca icosandra and Phyllanthus reticulatus as sensitizers was analyzed. Detailed structural and surface characterization of the ZnO nanorods were accomplished using X-ray diffraction (XRD) analysis and high resolution scanning electron microscopy (HRSEM). XRD results revealed that the synthesized ZnO material exhibited hexagonal crystal structure which was found to be highly stable and crystallite. The dye extracts were subjected to UV–Visible absorption spectroscopy and Fourier Transform Infrared (FTIR) analysis. The short-circuit photocurrent; the open-circuit photovoltage, and the power conversion efficiency of DSSC were measured using J-V measurement system.

Correlation between the Effectiveness of the Electron-Selective Contact and Photovoltaic Performance of Perovskite Solar Cells.

Metal halide perovskites (MHPs) are mixed electronic-ionic semiconductors with a remarkable photovoltaic potential that has led to a current world record efficiency surpassing 23%. This good performance stems from the combination of excellent light harvesting and relatively slow nonradiative recombination, which are characteristic of MHPs. However, taking advantage of these properties requires electron and hole transport materials that can efficiently extract charge with minimal photovoltage losses and recombination. It is well-known that n-type anatase TiO2 is a good electron-selective contact (ESC), although the fundamental reasons for its functioning are not completely clear to date. In this Letter, we investigate this issue by preparing perovskite-based solar cells with various n-type metal-oxide electron-selective contacts of different chemical nature and crystal structure. Our main finding is that the open-circuit photovoltage remains essentially independent of the nature of the contact for highly selective electron contacts, a fact that we attribute to a recombination rate that is mainly governed by the bulk of the MHPs. In contrast, replacement of the "standard" TiO2 contact by alternative contacts leads to lower short-circuit photocurrents and more pronounced hysteresis, related to enhanced surface recombination at less effective electron-selective contacts.

Effect of the Hydrogen Concentration on the Pd/n-InP Schottky Diode Photocurrent

The variation rate of the short-circuit photocurrent of Pd/n-InP Schottky diodes is studied as a function of the presence of hydrogen in a gas mixture with H2 concentrations of 1–100 vol %. It is shown that upon the simultaneous exposure of the Schottky diode to a hydrogen-containing gas mixture and to light (λ = 0.9 μm), the hydrogen concentration in the gas mixture and the Pd/n-InP diode photocurrent variation rate are related exponentially. The Schottky-diode response rate to the presence of hydrogen in the gas mixture increases with the illumination intensity.

Improving of the Photovoltaic Characteristics of Dye-Sensitized Solar Cells Using a Photoelectrode with Electrospun Porous TiO₂ Nanofibers.

Porous TiO2 nanofibers (PTFs) and dense TiO2 nanofibers (DTFs) were prepared using simple electrospinning for application in dye-sensitized solar cells (DSSCs). TiO2 nanoparticles (TNPs) were prepared using a hydrothermal reaction. The as-prepared PTFs and DTFs (with a fiber diameter of around 200 nm) were mixed with TNPs such as TNP-PTF and TNP-DTF nanocomposites used in photoelectrode materials or were coated as light scattering layers on the photoelectrodes to improve the charge transfer ability and light harvesting effect of the DSSCs. The as-prepared TNPs showed a pure anatase phase, while the PTFs and DTFs showed both the anatase and rutile phases. The TNP-PTF composite (TNP:PTF = 9:1 wt.%) exhibited an enhanced short circuit photocurrent density (Jsc) of 14.95 ± 1.03 mA cm−2 and a photoelectric conversion efficiency (PCE, η) of 5.4 ± 0.17% because of the improved charge transport and accessibility for the electrolyte ions. In addition, the TNP/PTF photoelectrode showed excellent light absorption in the visible region because of the mountainous nature of light induced by the PTF light scattering layer. The TNP/PTF photoelectrode showed the highest Jsc (16.96 ± 0.79 mA cm−2), η (5.9 ± 0.13%), and open circuit voltage (Voc, 0.66 ± 0.02 V).

Natural Dyes Extracted from Fruits of Phyllanthus reticulatus as Sensitizers in ZnO Nanorods Based Dye Sensitized Solar Cells

DSSCs are a promising class of photovoltaic cells with the capability of generating green energy at low production cost since no expensive equipment is required in their fabrication. Zinc oxide (ZnO) nanorods were synthesized by hydrothermal method and their perfomance as photoanodes in dye-sensitized solar cells (DSSCs) employing I-/I3- as electrolyte and the dye extracts from fruits of Phyllanthus reticulatus as sensitizers was analyzed. the structural and surface characterization of the ZnO nanorods were accomplished using X- ray diffraction (XRD) analysis and high resolution scanning electron microscopy (HRSEM). XRD results revealed that the synthesized ZnO material exhibited hexagonal crystal structure which was found to be highly stable and crystallite. The dielectric properties of the ZnO nanorods were analyzed. The dye extracts were subjected to UV-Visible absorption spectroscopy analysis. The short-circuit photocurrent, the open-circuit photovoltage, and the power conversion efficiency of DSSC were measured using J-V measurement system.

Blocking the Charge Recombination with Diiodide Radicals by TiO2 Compact Layer in Dye-Sensitized Solar Cells

The addition of a compact titanium dioxide (TiO2) layer between the fluorine-doped tin oxide (FTO) coated glass substrate and the mesoporous TiO2 layer in the dye-sensitized solar cell (DSC) based on the iodide/triiodide redox couple (I−/I3−) is known to improve its current-voltage characteristics. The compact layer decreases the recombination of electrons extracted through the FTO layer with I3− around the maximum power point. Furthermore, the short-circuit photocurrent was improved, which previously has been attributed to the improved light transmittance and/or better contact between TiO2 and FTO. Here, we demonstrate that the compact TiO2 layer has another beneficial effect: it blocks the reaction between charge carriers in the FTO and photogenerated diiodide radical species (I2−•). Using photomodulated voltammetry, it is demonstrated that the cathodic photocurrent found at bare FTO electrodes is blocked by the addition of a compact TiO2 layer, while the anodic photocurrent due to reaction with I2−• is maintained.

Влияние концентрации водорода на фототок диодов Шоттки Pd/n-InP

AbstractThe variation rate of the short-circuit photocurrent of Pd/ n -InP Schottky diodes is studied as a function of the presence of hydrogen in a gas mixture with H_2 concentrations of 1–100 vol %. It is shown that upon the simultaneous exposure of the Schottky diode to a hydrogen-containing gas mixture and to light (λ = 0.9 μm), the hydrogen concentration in the gas mixture and the Pd/ n -InP diode photocurrent variation rate are related exponentially. The Schottky-diode response rate to the presence of hydrogen in the gas mixture increases with the illumination intensity.

Enhanced photovoltaic performance of sol–gel-derived FTO/TiO2/BiFeO3 heterostructure thin film obtained via modifying thickness of TiO2 transport layer

BiFeO3 (BFO) is a promising photovoltaic material and TiO2 tends to be an efficient electronic transmission material in perovskite solar cells. In this paper, FTO/TiO2/BFO heterostructure thin films with various TiO2 thicknesses (0, 50, 100, and 150 nm, respectively) are prepared successfully via a sol–gel method. The effects of TiO2 layer thickness on the microstructure, insulating and photovoltaic properties are characterized. All the thin films possess a polycrystalline structure that matches well with the perovskite phase. Significant improvement can be achieved with the introduction of the TiO2 electron transport layer. Among all tested films, the one with 100 nm-TiO2 exhibited superior photovoltaic performance. The champion power conversion efficiency (η) of 3.67% with fill factor of 0.64 could be achieved with an open-circuit voltage (Voc) of 1.64 V and a short-circuit photocurrent (Jsc) of 3.50 mA/cm2. This can be ascribed to the favorable effect of TiO2 to the electron transport and restriction to the electron–hole recombination.

Mixed-phase Mesoporous TiO2 Film for High Efficiency Perovskite Solar Cells

Mesoporous scaffold structures have played great roles in halide perovskite solar cells(PSCs), due to the excellent photovoltaic performance and commercial perspective of mesoporous PSCs. Here, we reported a mixed-phase TiO2 mesoporous film as an efficient electron transport layer(ETL) for mesoporous perovskite solar cells. Due to the improved crystal phase, film thickness and nanoparticle size of TiO2 layer, which were controlled by varying the one-step hydrothermal reaction time and annealing time, the PSCs exhibited an outstanding short circuit photocurrent density of 25.27 mA/cm2, and a maximum power conversion efficiency(PCE) of 19.87%. It is found that the ultra-high Jsc attributes to the excellent film quality, light capturing and excellent electron transport ability of mixed-phase TiO2 mesoporous film. The results indicate that mix-phase mesoporous metal oxide films could be a promising candidate for producing effective ETLs and high efficiency PSCs.

Validity of density-functional-theory-based molecular modeling for UV/visible spectroscopy and rationale of panchromatic PbI64−(MeNH3+)4-structured molecular solar cells

Density-functional-theory-based molecular modeling verifies that perovskite solar cells (PSC) are composed of semiconducting and panchromatic layers constructed by van der Waals and Coulomb interactions (vdW&Clmb) between PbI64−(MeNH3+)4-derived species. Firstly we validate that DFT-based UV/vis spectral analysis is a useful approach for vdW&Clmb based on assignments of the fine-structured UV/vis spectrum of a benzene solution. The UV/vis spectral analysis of aggregated PbI64−(MeNH3+)4 proves that dimeric aggregates of [PbI64−(MeNH3+)4]2 have a panchromatic UV/vis spectrum of λ max ranging from 417 to 959 nm. Further analysis proves that the strong vdW&Clmb of PbI64−(MeNH3+)4 leads to unidirectional electron transport at the structured components such as the dimer of [PbI64−(MeNH3+)4]2, nc-TiO2/PbI64−(MeNH3+)4, and PbI64−(MeNH3+)4/spiro-OMeTAD. PbI64−(MeNH3+)4-structured solar cells should have a photoelectron diffusion length enhanced by the alignment of the frontier molecular orbitals in the structured PbI64−(MeNH3+)4 components, which supports remarkable short-circuit photocurrent, open-circuit voltage, and fill factor for the molecular-orbital-connected solar cell of HOTi9O18H/[PbI64−(MeNH3+)4]n/spiro-OMeTAD under solar-light irradiance.