Incident Photon To Charge Carrier Efficiency Research Articles

Manual Method for Measuring The External Quantum Efficiency for solar cells

Nowadays, the research related to the solar cells is oriented to the solar cell’s quantum efficiency (QE) or the Incident Photon to Charge Carrier Efficiency (IPCE) development. The determination of the external quantum efficiency (EQE) is fundamental to photovoltaic research [10]. This article proposes a fast conventional method to determine the external quantum efficiency (EQE) of a solar cell using a measuring bench (IPCE), such as the instruments and the measuring principle. The foundations necessary to study the important parts of EQE are built. The main equations and guiding principles of this measurement are reviewed.

Fabrication and properties of high efficiency dye-sensitized solar cells (DSSCs) with photon absorption optimization

Dye-sensitized solar cells (DSSCs) have attracted much attention because these unconventional solar cells exhibit high performance and have the potential for low-cost production. To achieve higher performances for solar cells based on organic dyes, comparable to those for solar cells based on the color spectrum, the light absorption of organic dyes is required. In a DSSC, the electrodes are surrounded by a thin shell and a dye monolayer for 3 colors of dyes. Based on the optical properties, the large absorption of light can be given in a colorless dye with a wavelength of the most extensive. Combination colors from three-band basic colors, such as red (R), green (G) and blue (B) can create the optimum light absorption. The Incident Photon-to-charge Carrier Efficiency (IPCE) will be high if the absorption spectrum graph of dye color is large too, therefore the Dye-Sensitized Solar Cell (DSSC) will produce photon current (If) or high short-circuit current (Isc). To ensure solid surface coverage, the dye must have a high absorption coefficient on TiO2. The electrodes can be maximized with reduced layer thickness so the possibility of recombination decreases with decreasing electrode thickness and thicker electrolytes with low vapor pressure can be applied. The longer the wavelength, the less absorption will cause a small portion of the sun’s spectrum to disappear. The experiment showed that a combination of three band colors of dye is obtained the largest light absorption. This black color proved to have the greatest light absorption. The experiment can result for the exhibit a high open-circuit voltage VOC of 320 mV, open-circuit current IOC of 0.045 mA, maximum voltage Vmax of 134 mV, maximum current Imax of 0.044 mA, maximum power Pmax of 5.89 μW, Fill Factor (FF) of 42 and a power conversion efficiency of 9.1%.

Enhanced photoelectrochemical performance of CdO-TiO2 nanotubes prepared by direct impregnation

A direct impregnation technique was adopted to prepare a series of CdO-TiO2 nanotubes. Self-organized TiO2 nanotubes were prepared using an optimized two-step anodization process. The morphology, crystallinity, elemental composition, and photoelectrochemical properties of the CdO-TiO2 nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis diffuse reflection spectra (UV–Vis DRS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and photoelectric cell (PEC) measurements. At lower Cd(NO3)2 concentration, no obvious CdO crystalline particle formed on the TiO2 NTbs surface, while the EDS and XPS measurements shows the increasing doping amount of CdO as the Cd(NO3)2 concentration increasing. At a relatively high precursor concentration (800 mM), the formation of particle clusters and nanocrystals on the surface of the TiO2 nanotubes could be easily detected, and the sample presented XRD diffraction peaks indicative of CdTiO3. Meanwhile, the Ti 2p XPS spectra displayed an obvious shift (∼0.3 eV), which could be attributed to the change in the lattice structure. A negative shift in the flatband potential (Vfb) and a decrease in charge carrier density were observed after doping. The maximum incident photon to charge carrier efficiency (IPCE) value calculated for the CdO-TiO2 nanotubes was 10.16%, much higher than that of pure TiO2 nanotubes.

Electrochemically synthesized mesoporous thin films of ZnO for highly efficient dye sensitized solar cells

In this work, nanostructured thin films of ZnO were electrochemically grown on FTO substrates. The morphology was tuned by modifying the synthesis parameters. The synthesis was carried out by applying Zn(NO3)·6H2O as the sole component of the aqueous electrolyte, avoiding the use of capping agents. The composition and morphology of the prepared ZnO were characterized by energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM), respectively. The as-deposited films were applied as electrodes in dye sensitized solar cells (DSCs). The performance of the cells was investigated by J×V curves and IPCE (incident photon to charge carrier efficiency) measurements. The SEM analysis demonstrated a direct relationship between ZnO morphology and Zn precursor concentration. It has been shown that the lower the concentration is, the more porous the morphology is. Increasing the amount of dye adsorbed on the ZnO decreased the power conversion efficiency of the final DSCs. The best cell presented the following parameters: open circuit voltage VOC=0.59V, short circuit current JSC=7.64mA/cm2, fill factor FF=50.41%, and power conversion efficiency PCE=2.27%.

Synthesis of multilayered TiO2 “donuts” for improved quantum-dot sensitized solar cells

In this paper, a simple method was developed to prepare the submicron-sized multilayered TiO2 “donuts” (MLTDs), which were constructed by orderly-arranged nanosheets with thickness of ~9nm. Based on the investigation of the time-dependent and other control experiments, a nucleation-assembling-growth mechanism was proposed to describe the formation of the MLTD structure. Then, the MLTDs were introduced into the quantum-dot (CdS/CdSe) sensitized solar cells (QDSSCs) as the photoanode materials. For comparison, QDSSCs based on the randomly assembled nanosheets-based microspheres (RATSs) and commercial P25 nanoparticles were also assembled. Maximum incident photon to charge carrier efficiency (IPCE) value of 57% was observed for CdS/CdSe co-sensitized MLTDs architectures, which was higher than those of RATSs and P25 (50% and 54%, respectively ). The enhanced IPCE observed in the MLTDs architectures was mainly attributed to the increased absorption of light. Moreover, the large pore size distribution of MLTDs might be beneficial for electrolyte penetration. Based on these advantages, MLTDs-based QDSSCs demonstrated the highest conversation efficiency of 4.5% in all the three types of QDSSCs.

Fluorene functionalized porphyrins as broadband absorbers for TiO2nanocrystalline solar cells

Three 9,9-dihexyl-9H-fluorene (DHF) functionalized zinc porphyrin dyes (coded as ZZX-N3, ZZX-N4, and ZZX-N5) were designed and synthesized for dye-sensitized solar cells. Then, DHF and benzoic acid were conjugated to the porphyrin ring through triple bonds to act as a spacer to elongate the π-conjugation and as an acceptor for an efficient electron injection, respectively. A bis(9,9-dihexyl-9H-fluorene-7-yl)amine (BFA) and a bis(4-hexylphenyl)amine (BPA) were further linked to DHF to act as electron donors in ZZX-N3 and ZZX-N4, respectively. ZZX-N5 did not have any electron donor and served as a reference. Moreover, ZZX-N3- and ZZX-N4-sensitized cells exhibited broader sunlight absorption than ZZX-N5, and as a result, higher photon-to-electricity efficiency (PCE) (ZZX-N3, 3.83%; ZZX-N4, 4.2%; ZZX-N5, 3.70%) was observed. The results are consistent with well-separated HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) in ZZX-N3 and ZZX-N4 than in ZZX-N5. However, the overall conversion efficiency of ZZX-N3- and ZZX-N4-sensitized cells was low, which is due to significant dye aggregation induced by the extra long alkyl-chains on the donor groups. This was evidenced by blue and red shifts of the absorption spectra of dye-coated TiO2 films. In addition, the extra long-chains also did not offer better shielding to prevent electron recombination of injected electrons with I3− in electrolyte as revealed by electrochemical impedance spectroscopy. When a co-sensitizer (coded as PBS) was used, a new peak corresponding to the absorption of PBS at 560 nm was observed on the incident photon to charge carrier efficiency (IPCE) spectra; however, the overall photovoltaic performance was not improved due to the significant decrease of dye-loading density of porphyrin dyes, indicating a need to break off the trade-off between dye-loading and light-harvesting.

Influence of structural and chemical properties on electron transport in mesoporous ZnO-based dye-sensitized solar cell

Two chemical bath deposition (CBD) solutions were prepared at two different temperatures of 60 and 80 °C for dye-sensitized solar cell (DSSC) application. The deposition time was varied from 12, 18, and 24 h. The X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis confirmed a transformation of hydrozincite into ZnO after calcined at 300 °C. The flower-like structure was observed by scanning electron microscopy (SEM) analysis. The ZnO photoanode deposited at 80 °C for 24 h showed the highest incident photon to charge carrier efficiency (IPCE) value of 5.25 %. The power conversion efficiency, η increased from 1.81 to 2.45 % for the photoanode deposited at 60 and 80 °C, respectively. The effective electron lifetimes, τeff of 6.36 ms was measured as much shorter than the TiO2-based DSSC (τeff of 25 to 160 ms). The effective electron diffusion coefficient, Deff, increased from 1.7 × 10−3 to 4.7 × 10−3 cm2.s−1 when the deposition temperature increases from 60 to 80 °C. Effective rate constant for recombination, keff of 157 s−1 was calculated for both samples. The results and analysis of the film’s surface structure, morphology, electron diffusion, and recombination inside the mesoporous ZnO photoanode proved the applicability of ZnO for the DSSC’s application.

Photovoltaic properties of glass forming pyranyliden derivatives in thin films

Organic solar cells based on solution processable materials could provide new low cost production method. Most popular materials are polymer P3HT and fullerene derivative PCBM. There is active study to find effective low molecular weight materials. Instead of planar structure, most of the research is made on bulk heterojunction samples as they are providing better efficiency. In our work we have studied three newly synthesized materials consisting 2-tert-butyl-6-methyl-4H-pyran-4-ylidene fragment. Each compound has different electron acceptor group. From photoconductivity experiments its threshold values were obtained. For photovoltaic experiments bulk heteroj unction samples containing investigated compounds mixed with PCBM were made. Best results with Incident Photon to Charge Carrier Efficiency (IPCE) larger than 0.4% at wavelength between 390 and 570 nm were obtained for system containing compound with malononitrile as electron acceptor group. Still, efficiency could be greatly improved as IPCE spectral dependence is not repeating absorption spectrum which show that generated charge carriers extraction from the sample was limited.

Photoelectrochemical properties of oxide films formed by anode plasma electrolytic oxidation on titanium in water solutions

It is shown that films of titanium dioxide obtained by anodic plasma electrolytic processing of commercial titanium in an aqueous solution of ammonium chloride are photosensitive. Incident photon to charge carrier efficiency (IPCE) in the near ultraviolet (366 nm) reached 8.5%. Magnitude of the photocurrent generated by the films obtained under optimum processing conditions decreases no more than 20% at the transition from the ultraviolet to the mixed light.

Photoelectrocatalytic properties of Ag nanoparticles loaded TiO 2 nanotube arrays prepared by pulse current deposition

A pulse current deposition technique was adopted to construct highly dispersed Ag nanoparticles on TiO 2 nanotube arrays which were prepared by the electrochemical anodization. The morphology, crystallinity, elemental composition, and UV–vis absorption of Ag/TiO 2 nanotube arrays were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and diffuse reflectance spectra (DRS). In particular, the photoelectrochemical properties and photoelectrocatalytic activity under UV light irradiation and the photocatalytic activity under visible light irradiation for newly synthesized Ag/TiO 2 nanotube arrays were investigated. The maximum incident photon to charge carrier efficiency (IPCE) value of Ag/TiO 2 nanotube arrays was 51%, much higher than that of pure TiO 2 nanotube arrays. Ag/TiO 2 nanotube arrays exhibited higher photocatalytic activities than the pure TiO 2 nanotube arrays under both UV and visible light irradiation. The photoelectrocatalytic activity of Ag/TiO 2 nanotube arrays under UV light irradiation was 1.6-fold enhancement compared with pure TiO 2 nanotube arrays. This approach can be used in synthesizing various metal-loaded nanotube arrays materials.

Sonoelectrochemical synthesis of highly photoelectrochemically activeTiO2 nanotubes by incorporating CdS nanoparticles

Self-organized anodic TiO2 nanotube arrays (TiO2NTs) are functionalized with CdS nanoparticle based perfusion and depositionthrough a single-step sonoelectrodeposition method. Even controlled at50 °C, CdS nanoparticles with smaller size and more homogeneous distribution are successfullysynthesized in dimethyl sulfoxide (DMSO) under ultrasonic irradiation. Moreover,TiO2 nanotubes can be filled with nanoparticles because of the ultrasonic effect. The CdS incorporatedTiO2NTs (CdS–TiO2NTs)effectively harvest solar light in the UV as well as the visible light (up to 480 nm) region. Compared withpure TiO2NTs, a more than ninefold enhancement in photocurrent response is observed using the CdS–TiO2NTs. Maximum incident photon to charge carrier efficiency (IPCE)values of 99.95% and 9.85% are observed respectively for CdS–TiO2 nanotubesand pure TiO2NTs. The high value of IPCE observed with the CdS–TiO2NTs is attributed to the increased efficiency of charge separation and transport ofelectrons. A schematic diagram is proposed to illustrate the possible process ofCdS formation in nanotubes under sonochemical and electrochemical conditions.

Photosensitization of TiO2 Nanostructures with CdS Quantum Dots: Particulate versus Tubular Support Architectures

AbstractTiO2 nanotube arrays and particulate films are modified with CdS quantum dots with an aim to tune the response of the photoelectrochemical cell in the visible region. The method of successive ionic layer adsorption and reaction facilitates size control of CdS quantum dots. These CdS nanocrystals, upon excitation with visible light, inject electrons into the TiO2 nanotubes and particles and thus enable their use as photosensitive electrodes. Maximum incident photon to charge carrier efficiency (IPCE) values of 55% and 26% are observed for CdS sensitized TiO2 nanotube and nanoparticulate architectures respectively. The nearly doubling of IPCE observed with the TiO2 nanotube architecture is attributed to the increased efficiency of charge separation and transport of electrons.

Photovoltaic devices based on PPHT: ZnO and dye-sensitized PPHT: ZnO thin films

We have investigated the optical and photovoltaic properties of hybrid organic solar cells based on the blend of poly-3-phenylhydrazone thiophene (PPHT):ZnO and PPHT:dye:ZnO. In this architecture, ZnO and PPHT were the electron acceptor and donor, respectively, and dye was used both as acceptor as well as sensitizer to enhance the photon absorption in visible region. These results showed that on incorporation of dye in PPHT: ZnO composite the light absorption, exciton separation and photocurrent under white light dramatically enhanced. The dependence of photovoltaic parameters on the weight fraction of ZnO in PPHT: ZnO was also investigated. It is found that the device with 45% of ZnO in both composites exhibits the best photovoltaic performance. The thermal annealing of PPHT: ZnO-based device gives rise to a significant increase in power conversion efficiency as evident from the measurements of incident photon to charge carrier efficiency (IPCE) spectra and current–voltage characteristics under illumination. The absorption band of PPHT: ZnO blend becomes stronger and the absorption peak ascribed to PPHT is shifted towards the longer wavelength region (red shift) upon thermal annealing. The effect of solvent used for thin-film fabrication was also studied. It is also observed that the fluorescence (FL) quenching and solar cell efficiency were found to be strongly dependent on the solvent used for spin coating.