Higher IPCE Research Articles

Biomass-derived carbon (BC) modified CoWO4 nanoparticles composites for improved performance of dye-sensitized solar cells

Semiconductor-based photoanodes have sparked a lot more interest in the energy and environmental fields. A hydrothermal method was used to construct cobalt tungstate (CoWO4)/bio carbon (BC) nanocomposites. PXRD, SEM, UV–Vis DRS, and PL analyses are used to properly characterise the structural, morphological, and autoelectric properties of the synthesized samples. Because of the synergistic contact between CoWO4 and BC, this effective excition separation leads to increased photovoltaic activity. According to the XRD and TEM results, wolframite monoclinic structure with nanosized individual particles in the range of 30–40 nm was homogeneously adorned on the surface of BC nanosheets. By using dye-sensitized solar cells (DSSCs) as working electrodes, the photovoltaic properties of the cells were studied. The CoWO4/BC photoanode developed demonstrated high power conversion efficiency (7.01%), IPCE (73.21%), and long-term stability. In addition, the CoWO4/BC photoanode demonstrated high electrocatalytic activity, low resistance, and a high charge carrier process. The enhanced methodology was also thoroughly described.

Biomass-derived carbon (BC) boosted catalytic properties of zinc tungstate (ZnWO4) hybrid photoanodes for accelerating the triiodide reduction in dye-sensitized solar cells

Herein, efficient ZnWO4 nanotubes incorporated/BC sheets hybrid photoanodes were designed by controlling the surface charges of the two individual materials via facile hydrothermal method. The prepared hybrid nanocomposites have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, photoluminescence (PL) and UV–Visible spectroscopy. XRD and TEM results suggest that monoclinic crystalline structure with 10–15 nm diameter of ZnWO4 nanotubes were uniformly decorated on the outer surface of BC sheet. The BC layer has had a significant impact on the structure and properties of the material, including lattice extension, band-gap reduction, fluorescence enhancement, and photovoltaic activity. The photovoltaic properties of dye-sensitized solar cells were investigated by applying them on the working electrodes. The developed ZnWO4/BC photoanode demonstrated high power conversion efficiency (7.61%), IPCE (78.21%), and long-term stability. The improved mechanism of the proposed photoanode materials are also discussed in detail.

Fabrication of WO3 nanotubes/graphene oxide nanosheets hybrid structures: Enhanced solar conversion efficiency in dye sensitized solar cell

In this article, photovoltaic performance driven reduced graphene oxide (rGO) induced tungsten oxide (WO3) hybrid nanocomposites were synthesized through one step microwave irradiation method for the dye sensitized solar cell (DSSC) application. Characterization of the structural and morphological was investigated through XRD, SEM, EDAX, HRTEM, XPS, Raman, and BET analysis were used to confirm that the nanocomposite was successfully developed. The results suggest that WO3 nanotubes decorated rGO sheets have a high electrical conductivity and a large effective surface area. The developed WO3/rGO photoanode showed a high power conversion efficiency (9.21 ± 0.001%), high IPCE (79.21%) and long term stability. The working mechanism of the proposed materials was also discussed in brief.

In Situ Integration of ReS2/Ni3S2 p-n Heterostructure for Enhanced Photoelectrocatalytic Performance.

The excellent light absorption, low electron-hole recombination rate, and fast reaction kinetics of photogenerated charges are urgently needed for photoelectrochemical (PEC) water splitting. Herein, a novel p-n heterostructure photoelectrode (ReS2/Ni3S2) is constructed via a one-step hydrothermal method, which shows remarkable HER activity under illumination such as a low overpotential (η10) of 106 mV, high IPCE of 10-15%, and good stability. High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) reveal that the intimate interface and strong electron interaction between ReS2 and Ni3S2 can enhance the light adsorption and provide abundant active sites. The transient absorption (TA) spectroscopy and impedance spectroscopy analyses (EIS) demonstrate the prolonged carrier lifetime and fast charge transfer. All of these are responsible for the improvement of reaction kinetics. This work provides a brand new avenue to explore efficient photoelectrocatalysts for water splitting.

Relationship between photo-physical and electrochemical properties of D-π-A compounds regarding solar cell applications. 1. Substituent type effect in photovoltaic performance.

Studying the electrochemical characteristics is an important step for determining interactions between molecules and the chemical environment. Moreover, the electrochemical evaluation of dyes is highly needed to establish the behavior of electro-active chemical species inside dye-sensitized solar cells (DSSCs). Four compounds, M8-1, M8-2, M8-O1, and M8-O2 (with a common organic structure (E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(phenylamino)-9H-fluoren-2-yl)vinyl)thiophen-2-yl)acrylic acid), are studied in two solvents, tetrahydrofuran (THF) and dimethylsulfoxide (DMSO). Among the studied compounds, M8-1 has highlighted characteristics compared with the others: its ground and excited states oxidation potential are the highest (1.14 and -1.22V, respectively). Also, it shows the lowest energy gap between the excited state oxidation potential and the TiO2 conduction band. Relating to the substituent effect, the shorter the length, the higher the energetic difference in the electronic transition (M8-1 and 2). Comparing characteristics through quantum chemistry, the values obtained in DMSO are the most predictable. The injection energies signal that M8-1 is the best injector. The performances in solar cells are measured in three TiO2 materials: Degussa (D-TiO2), active opaque (A-TiO2), and transparent (T-TiO2). The IPCE results show the A > T > D average tendency, and the family of substituted alkyl has higher values than the alcoxyl one. Furthermore, in the first family the methyl substituent has a higher value than the ethyl one. M8-1 has the highest IPCE value, on average. In terms of efficiency, the alkyl substituted family again has higher values than the alcoxyl family. On average, the methyl substituent has a higher value than the ethyl one in both families. M8-1 has the highest efficiency value.

TiO2 photoanodes with exposed {0 1 0} facets grown by aerosol-assisted chemical vapor deposition of a titanium oxo/alkoxy cluster

TiO2 photoanodes with {0 1 0} facets exposed show high photoelectrochemical performance and IPCE of 100% at 350 nm.

Two-dimensional SnS2 nanosheets arrays as photoelectrode by low temperature CVD method for efficient photoelectrochemical water splitting

Two-dimensional (2D) metal dichalcogenides have attracted considerable attention in photoelectrochemical (PEC) water splitting because of their particular layer structure and strong interaction with light. Herein, in this article, we report a facile chemical vapor deposition (CVD) method, via low boiling point SnCl4·5H2O and S powders as precursors. Light trapping nanosheets arrays SnS2 (SnS2⊥FTO) have been deposited on conductive substrate. By optimizing the preparation conditions, included deposition temperature, flow rate of carrier gas and the distance between the Sn source and growth substrate. Moreover, the key factors to affect the growth of SnS2 in CVD process have been investigated in detail. In PEC measurements, the as-synthesized thin film of 450 °C, 50 sccm, 11 cm shows the highest photocurrent density of up to 3.68 mA cm−2 at 0.5 V vs. SCE under the sunlight and high IPCE of up to 33.11% at 365 nm. The values much higher than conventional photoelectrode by spin-coating (SnS2//FTO), which achieved efficient photoelectrochemical water splitting under the sunlight.

Enhanced performance of BiFeO3@nitrogen doped TiO2 core-shell structured nanocomposites: Synergistic effect towards solar cell amplification

A core-shell nano-heterostructured perovskite BiFO3@nitrogen doped mesoporous TiO2 (BFO/n-TiO2) hydrothermally assembled via using citric acid and polyethlene glycol (PEG) was characterized through XRD, TEM, FTIR, UV–Vis diffuse reflectance, IPCE, N2 adsorption and impedance spectroscopy. It has been demonstrated that the photovoltaic yield of the 90%N-TiO2-10%BFO electrode achieves a power conversion efficiency (PCE) of 4.5%, which is 1.85, 2.5, 3 and 1202 times higher than those of 10%N-TiO2-90%BFO, 50%N-TiO2-50%BFO, n-TiO2 and pristine BFO, respectively. It is acknowledged that the former electrode exhibits a significant visible light harvesting capability, lowest band gap (Eg = 2.0 eV) as well as the highest IPCE% (36% at 460 nm) values. The EIS and capacitance results illustrated that 90%N-TiO2-10%BFO owns excessive charge carriers (e− − h+); compared to rest of nanocomposites, with a great sparation, to assist boosting the PCE value. This was highly aided by the surface defects seen on the core represented by BFO, which worked as a rational carrier trapper between the N719 dye and the n-TiO2 shell structure. The surface texturing properties of the nanocomposite forming the 90%N-TiO2-10%BFO electrode including SBET (Asahi et al., 2001) and pore volume (0.48 cm3 g−1) have shared significantly in improving the conversion efficiency of such p-n heterojunction based solar cells; which never achieved as such in all BFO-based solar cell devices, with acceptable tunability.

Influence of transparent conductive oxide layer on the inverted perovskite solar cell using PEDOT: PSS for hole transport layer

The Optical and electrical effects of the transparent conductive oxide layer on the performance of inverted perovskite solar cells (PSCs) were investigated. We have utilized transparent conductive layers of ITO and FTO layers with the same sheet resistance. The PSCs with ITO-coated glass achieved the 10.8% conversion efficiency, which is higher than that with FTO one (9.0%). The first finding is that the PSCs with ITO-coated glass substrate has lower resistances in series and parallel than those with ITO coated one. The second finding is that ITO-coated glass substrate has a higher transmittance than FTO, the PSCs with ITO-coated glass substrate can obtain the high IPCE value. PSCs using FTO-coated glass substrate did not show hysteresis in the I-V curves. However, hysteresis was caused using ITO-coated glass substrate, due to the slight differences between ITO and FTO about the roughness of the HTL interface in contact with the perovskite layer.

Wide-Range Near-Infrared Sensitizing 1 H-Benzo[ c, d]indol-2-ylidene-Based Squaraine Dyes for Dye-Sensitized Solar Cells.

NIR absorbing squaraine dyes SQ1-SQ7 having 1 H-benzo[ c, d]indol-2-ylidene as a donor moiety were designed for application in DSSCs. Annulation of the benzene ring to an 3 H-indolium-based anchor moiety led to a red-shifted and broadened absorption band on TiO2 film, which were reflected in the improved short-circuit current density of SQ2 (6.22 mA cm-2) compared to the nonbenzene fused derivative SQ1 (4.39 mA cm-2). Although the introduction of a butoxy (SQ4: 806 nm) or dialkylamino group (SQ5-SQ7: 815-820 nm) to the 1 H-benzo[ c, d]indol-2-ylidene-based donor moiety resulted in red-shifted absorption maxima in ethanol compared to the nonsubstituted derivative SQ2 (784 nm), the HOMO energy level of SQ4-SQ7 gave rise to an undesirable approximation to the redox potential of I-/I3-. Thus, the butoxy (SQ4: 0.56) and dialkylamino (SQ5-SQ7: 0.25-0.30) derivatives had relatively lower conversion efficiencies. Since the 2-ethylhexyl derivative SQ3 exhibited red-shifted absorption (λmax: 796 nm), suitable HOMO and LUMO energy levels, and relatively efficient restriction of charge recombination, this dye achieved the highest conversion efficiency (1.31%), along with a high IPCE response of over 20% over a wide range from 640 to 860 nm and an onset of IPCE at 1000 nm.

Asymmetric double donor-π-acceptor dyes based on phenothiazine and carbazole donors for dye-sensitized solar cells

Four organic dyes with asymmetric double donor-π-acceptor system were designed, synthesized and utilized in dye-sensitized solar cells (DSSCs), where phenothiazine and carbazole were introduced as double donors, butyl or octyl chain as the linker and cyanoacetic acid or rhodanine acetic acid as the electron acceptor. The design of double donor-π-acceptor system contributes to a distinctive increase of the molar extinction coefficient and benefits light-harvesting capability of these dyes. Due to superior electron injection efficiency, CPC-series dyes with cyanoacetic acid acceptor exhibit broader IPCE spectra and high IPCE responsive value compared with rhodanine-3-acetic acid acceptor, leading to higher JSC. Long alkyl chain favors antiaggregation effect and low charge recombination rate is observed for dyes with octyl chain which display higher VOC than those with butyl chain. Among four dyes, dye with octyl chain and cyanoacetic acid acceptor exhibits the highest short-circuit photocurrent density (9.64 mA cm−2) and open-circuit photovoltage (720 mV), leading to the best overall power conversion efficiency of 4.76%.

Multi-layer monoclinic BiVO4 with oxygen vacancies and V4+ species for highly efficient visible-light photoelectrochemical applications

The utilization of solar energy into photoelectrochemical (PEC) water splitting is a popular approach to store the sustainable energy and minimize the dependence of fossil fuels. Herein, multi-layer BiVO4 films were synthesized by multi-cycle electrodeposition following by annealing at high temperature. Multi-layer BiVO4 films have monoclinic scheelite structure, and the morphology is changed from densely compact film to sponge-like network, and then bulk structure with the increase of electro-deposited layers. X-ray photoelectron spectra indicate the presence of abundant oxygen vacancies and V4+ species in multi-layer BiVO4, especially for 3-layer one. For visible-light PEC performance, 3-layer BiVO4 shows the highest photocurrent among the samples, i.e. up to 5.80mA/cm2 in sulfite oxidation and 1.79mA/cm2 in water splitting at 1.23V versus a reverse hydrogen electrode (RHE) under 1 sun irradiation (100mW/cm2), with very high IPCE achieved nearly 83% and 25% (at 420nm), respectively. The extremely high PEC performance of 3-layer BiVO4 is attributed to its morphology of sponge-like network and the modulated band structure by the oxygen vacancies and V4+ species. Moreover, the multi-layer BiVO4 also shows very high photostability. This work provides a multi-layer-construction method for highly visible-light-active PEC anodes for practical applications.

Low-Temperature Synthesis of Bismuth Chalcohalides: Candidate Photovoltaic Materials with Easily, Continuously Controllable Band gap.

Although bismuth chalcohalides, such as BiSI and BiSeI, have been recently attracting considerable attention as photovoltaic materials, the methods available to synthesize them are quite limited thus far. In this study, a novel, facile method to synthesize these chalcohalides, including BiSBr1−xIx solid solutions, at low temperatures was developed via the substitution of anions from O2− to S2− (or Se2−) using bismuth oxyhalide precursors. Complete phase transition was readily observed upon treatment of BiOI particles with H2S or H2Se at surprisingly low temperatures of less than 150 °C and short reaction times of less than 1 h, producing BiSI and BiSeI particles, respectively. This method was also applied for synthesizing BiSBr1−xIx, where continuous changes in their band gaps were observed depending on the ratio between iodine and bromine. The composition of all elements (except oxygen) in the chalcohalides thus produced was almost identical to that of the oxyhalide precursors, attributed to the suppressed volatilization of halogens at such low temperatures. All chalcohalides loaded on FTO clearly exhibited an anodic photocurrent in an acetonitrile solution containing I−, attributed to their n-type nature, e.g., the BiSI electrode exhibited high IPCE (64% at 700 nm, +0.2 V vs. Ag/AgCl).

Alkyl chain length dependence of the charge-transfer, recombination and electron diffusion length on the photovoltaic performance in double donor-acceptor-based organic dyes for dye sensitized solar cells

A series of double donor-acceptor organic dyes (C4C12) have been synthesized to investigate the influence of the alkyl chain length between the two chromophores on the performance of dye sensitized solar cells (DSSCs). The chain length dependent performance was investigated further using the electrochemical impedance and stepped light induced transient measurement methods. Dye with longer alkyl chain (C6C12) shows a broader and higher IPCE as well as photo-current density (Jsc) with an enhanced photovoltage (Voc) relative to the reference PTZ-S. In contrast, C4 with shorter alkyl chain presents a relatively low IPCE within the whole spectral region, along with low Jsc and Voc, which predominately arising from the short electron diffusion length with significant electron loss during charge transport. The higher Jsc and Voc obtained with the devices incorporating C10 and C12 dyes with long alkyl chain resulted in a higher conversion efficiencies of 4.02% and 4.03%, respectively, (3.14% for single donor-acceptor dye PTZ-S). Density functional theory simulations were also performed to examine the effect of the alkyl chain length on electrochemical and optical properties of the dyes. Adsorption studies of the dyes on TiO2 clusters were carried out to explain the variation in Jsc with the alkyl chain length.

Effects of spin-coating speed on the morphology and photovoltaic performance of the diketopyrrolopyrrole-based terpolymer

Polymer solar cells (PSCs) were fabricated by combining a diketopyrrolopyrrole-based terpolymer (PTBT-HTID-DPP) as the electron donor, and [6,6]-phenyl C 61 butyric acid methyl ester (PC 61 BM) as the electron acceptor, and the power conversion efficiency (PCE) of 4.31% has been achieved under AM 1.5 G (100 mW cm -2 ) illumination condition via optimizing the polymer/PC 61 BM ratio, the variety of solvent and the spin-coating speed. The impact of the spin-coating speed on the photovoltaic performance of the PSCs has been investigated by revealing the effects of the spin-coating speed on the morphology and the absorption spectra of the polymer/PC 61 BM blend films. When the thickness of the blend films are adjusted by spin-coating a fixed concentration with different spin-coating speeds, the blend film prepared at a lower spin-coating speed shows a stronger absorption per unit thickness, and the correspond device shows higher IPCE value in the longer-wavelength region. Under the conditions of similar thickness, the blend film prepared at a lower spin-coating speed forms a more uniform microphase separation and smaller domain size which leads to a higher absorption intensity per unit thickness of the blend film in long wavenumber band, a larger short-circuit current density ( J sc ) and a higher power conversion efficiency (PCE) of the PSC device. Noteworthily, it was found that spin-coating speed is not only a way to control the thickness of active layer but also an influencing factor on morphology and photovoltaic performance for the diketopyrrolopyrrole-based terpolymer.

A SrTiO3 photoanode prepared by the particle transfer method for oxygen evolution from water with high quantum efficiencies.

A photoanode prepared from flux-synthesized Al-doped SrTiO3 by the particle transfer method with a Ta contact layer exhibited a high IPCE of 69% at 320 nm. The photocatalytic activity of SrTiO3 particles was very sensitive to the synthesis method used to make the SrTiO3 particles, while its photoelectrochemical performance was not.

High IPCE Performance of Photosensitized Dyes Having Trifluoromethylacrylic Acid as an Acceptor-anchor Moiety

Abstract Novel photosensitized dyes having trifluoromethylacrylic acid as an acceptor-anchor moiety (MCL26–29) are synthesized. These dyes seem to suppress the back-donation currents from the conduction band of TiO2 semiconductor to the electrolyte. Their fabricated dye-sensitized solar cells (DSCs) show high IPCE performances (MCL27; over 80% between 400–520 nm, max 90% at 465 nm). In particular, the high IPCE properties are compared with more than 80 article examples.

Fabrication of dye sensitized solar cells with different anchoring mode based triphenylamine dyes

Two new organic sensitizers of type D-π-A (Donor-π-Acceptor) and D-(π-A)2 were designed and synthesized to understand the effect of anchoring mode towards TiO2 film which leads to influence the efficiency of the fabricated dye sensitized solar cells. These dyes were synthesized based on the triphenylamine as electron donor, phenylhydrazine as π-conjugated spacer and 4-iodobenzoic acid as anchoring/acceptor group and characterized by 1H, 13C NMR and mass spectroscopy studies. The optical absorption of sensitizers shows red shift as well as high molar extinction co-efficient with extension of the π-conjugation and the quantum chemical calculation studies were performed to provide sufficient driving force for electron injection into conduction band of TiO2. The DSSC based on type D-(π-A)2 shows power conversion efficiency (PCE = η) 1.07% under simulated AM 1.5 G; due to more positive HOMO values, higher IPCE values, high adsorption capacity on TiO2 as well as longer electron life time of dye.

Theoretical study of benzene/thiophene based photosensitizers for dye sensitized solar cells (DSSCs)

Complex organic compounds with benzene/thiophene as pi-segments are inspected as photosensitizers for applications in dye sensitized solar cells. To better understand the charge transport process involved in the dye sensitized solar cells, we used the results of Kohn–Sham density functional theory and time-dependent density functional theory (DFT) studies of benzene/thiophene based sensitizers as well as the dye bound to a TiO2 nano cluster. We investigated the electronic structures and UV–Vis spectra of the sensitizers alone and linked to the cluster. We also showed energy level diagrams, the major transitions of molecular orbitals and free energy calculation of the electron transfer from the sensitizer to the conduction band of the TiO2. The results show that LUMO of the dyes is greater than the conduction band of TiO2 indicating that a full charge transfer from dyes to the conduction band of TiO2 is thermodynamically allowed. The calculated results also indicate that D3 is the most plausible sensitizer due to the most negative ΔGinject (0.91 eV) and a larger LHE value (0.95), which results in a higher IPCE.

New organic dyes with high IPCE values containing two triphenylamine units as co-donors for efficient dye-sensitized solar cells

New bis-TPA-based organic dyes for DSSCs showed high IPCE values dependent on π-conjugation.