A review of solar thermal technologies Thirugnanasambandam, Mirunalini; Iniyan, S.; Goic, Ranko
Renewable & sustainable energy reviews,
2010, 2010-01-00, 20100101, Letnik:
14, Številka:
1
Journal Article
Recenzirano
The use of solar energy in recent years has reached a remarkable edge. The continuous research for an alternative power source due to the perceived scarcity of fuel fossils is its driving force. It ...has become even more popular as the cost of fossil fuel continues to rise. The earth receives in just 1
h, more energy from the sun than what we consume in the whole world for 1 year. Its application was proven to be most economical, as most systems in individual uses requires but a few kilowatt of power. This paper reviews the present day solar thermal technologies. Performance analyses of existing designs (study), mathematical simulation (design) and fabrication of innovative designs with suggested improvements (development) have been discussed in this paper.
Exciting progress has been made in the area of solar fuel generation by CO
reduction. New photocatalytic materials containing well-defined surface catalytic sites have emerged in recent years, ...including heterogenized molecular catalysts and single atom catalysts. This Feature Article summarizes our recent research in this area, together with brief discussions of relevant literature. In our effort to obtain heterogenized molecular catalysts, a diimine-tricarbonyl Re(I) complex and a tetraaza macrocyclic Co(III) compound were covalently attached to different surfaces, and the effects of ligand derivatization and surface characteristics on their structures and photocatalytic activities were investigated. Single atom catalysts combine the advantages of homogeneous and heterogeneous catalysis. A single-site cobalt catalyst was prepared on graphitic carbon nitride, which demonstrated excellent activity in selective CO
reduction under visible-light irradiation. Doping carbon nitride with carbon was found to have profound effects on the structure and activity of the single-site cobalt catalyst. Our research achievements are presented to emphasize how spectroscopic techniques, including infrared, UV-visible, electron paramagnetic resonance, and X-ray absorption spectroscopies, could be combined with catalyst synthesis and computation modeling to understand the structures and properties of well-defined surface catalytic sites at the molecular level. This article also highlights challenges and opportunities in the broad context of solar CO
reduction.
Intermolecular charge-transfer excitons play a central role in determining the performance of organic solar cells as their voltage-dependent formation, dissociation, and recombination dynamics ...contribute to photocurrent generation, radiative/nonradiative voltage losses, and photovoltaic fill factor. Here, we explore the properties of brightly-emitting wide energy gap (>2 eV) charge transfer excitons by measuring the voltage-dependent photoluminescence, photocurrent, and ultrafast pump–probe transient absorption spectra of organic solar cells employing five UV-absorbing donor molecules that differ only by the length of the oligophenylene or acene group at their core. We find that organic solar cells with a strong correlation between their voltage-dependent photocurrent and charge-transfer exciton photoluminescence have low photovoltaic fill factors as they require voltage to facilitate efficient charge-transfer exciton dissociation. In contrast, solar cells that are efficient can readily generate charges without an applied field and have a separate population of tightly-bound charge-transfer excitons that are responsible for emission. Furthermore, considering that the sum of all excitation loss rates (i.e., recombination and charge extraction) must be equal to the excitation generation rate in the steady state, these voltage-dependent data allow us to solve for the voltage-dependent fate of all excitations in the solar cells and estimate upper and lower bounds for geminate and non-geminate recombination, respectively.
Abstract
We report a precious‐metal‐free molecular catalyst‐based photocathode that is active for aqueous CO
2
reduction to CO and methanol. The photoelectrode is composed of cobalt phthalocyanine ...molecules anchored on graphene oxide which is integrated via a (3‐aminopropyl)triethoxysilane linker to p‐type silicon protected by a thin film of titanium dioxide. The photocathode reduces CO
2
to CO with high selectivity at potentials as mild as 0 V versus the reversible hydrogen electrode (vs RHE). Methanol production is observed at an onset potential of −0.36 V vs RHE, and reaches a peak turnover frequency of 0.18 s
−1
. To date, this is the only molecular catalyst‐based photoelectrode that is active for the six‐electron reduction of CO
2
to methanol. This work puts forth a strategy for interfacing molecular catalysts to p‐type semiconductors and demonstrates state‐of‐the‐art performance for photoelectrochemical CO
2
reduction to CO and methanol.
A new pentad array designed to exhibit panchromatic absorption and charge separation has been synthesized and characterized. The array is composed of a triad panchromatic absorber (a ...bis(perylene-monoimide)-porphyrin) to which are appended an electron acceptor (perylene-diimide) and an electron donor/hole acceptor (bacteriochlorin) in a crossbar arrangement. The motivation for incorporation of the bacteriochlorin versus a free-base or zinc chlorin utilized in prior constructs was to facilitate hole transfer to this terminal unit and thereby achieve a higher yield of charge separation across the array. The intense S0 → S1 (Qy) band of the bacteriochlorin also enhances absorption in the near-infrared spectral region. Due to synthetic constraints, a phenylethyne linker was used to join the bacteriochlorin to the core porphyrin of the panchromatic triad rather than the diphenylethyne linker employed for the prior chlorin-containing pentads. Static and time-resolved photophysical studies reveal enhanced excited-state quenching for the pentad in benzonitrile and dimethyl sulfoxide compared to the prior chlorin-containing analogues. Success was only partial, however, as a long-lived charge separated state was not observed despite the improved energetics for the final ground-state hole/electron-shift reaction. The apparent reason is more facile competing charge-recombination due to the shorter bacteriochlorin – porphyrin linker that increases electronic coupling for this process. Furthermore, the studies highlight design criteria for balancing panchromatic absorption and long-lived charge separation in molecular architectures for solar-energy conversion.
Abstract
Two key interfaces in flexible perovskite solar cells (f‐PSCs) are mechanically reinforced simultaneously: one between the electron‐transport layer (ETL) and the 3D metal‐halide perovskite ...(MHP) thin film using self‐assembled monolayer (SAM), and the other between the 3D‐MHP thin film and the hole‐transport layer (HTL) using an in situ grown low‐dimensional (LD) MHP capping layer. The interfacial mechanical properties are measured and modeled. This rational interface engineering results in the enhancement of not only the mechanical properties of both interfaces but also their optoelectronic properties holistically. As a result, the new class of dual‐interface‐reinforced f‐PSCs has an unprecedented combination of the following three important performance parameters: high power‐conversion efficiency (PCE) of 21.03% (with reduced hysteresis), improved operational stability of 1000 h
T
90
(duration at 90% initial PCE retained), and enhanced mechanical reliability of 10 000 cycles
n
88
(number of bending cycles at 88% initial PCE retained). The scientific underpinnings of these synergistic enhancements are elucidated.
We report that Kesterite-type based thin film solar cell technologies are mainly based on polycrystalline absorber layers. A promising low cost alternative technology uses Cu2ZnSn(SxSe1-x)4 (CZTSSe) ...monograins (single crystals of 20–100 μm size) which are fixed in a polymer matrix to form a flexible solar cell. The Cu/Zn disorder is discussed as a possible reason for band tailing causing voltage losses limiting the efficiency of CZTSSe-based devices. The experimental determination of the order parameter Q which is a quantitative measure of Cu/Zn disorder, requires a differentiation between the isoelectronic cations Cu+ and Zn2+. An in-depth analysis of neutron diffraction data allows the determination of type and concentration of intrinsic point defects including a distinction between Cu and Zn. Neutron diffraction requires large sample volumes, thus monograins offer the unique possibility to correlate structural disorder in CZTSSe with device performance parameters. In this study we tackle the influence of grinding the monograins on stoichiometry deviations, the Cu/Zn disorder as well as intrinsic point defects and optoelectronic properties of CZTSSe monograins. Moreover, an easy methodology based on Raman scattering spectroscopy is proposed for the assessment of Cu/Zn disorder in the CZTSSe compounds.
This work describes an ab initio principle computational examination of the optical, structural, elastic, electronic and mechanical characteristics of aluminum-based compounds AlRFsub.3 (R = N, P) ...halide-perovskites. For optimization purposes, we used the Birch–Murnaghan equation of state and discovered that the compounds AlNFsub.3 and AlPFsub.3 are both structurally stable. The IRelast software was used to compute elastic constants (ECs) of the elastic properties. The aforementioned compounds are stable mechanically. They exhibit strong resistance to plastic strain, possess ductile nature and anisotropic behavior and are scratch-resistant. The modified Becke–Johnson (Tb-mBJ) approximation was adopted to compute various physical properties, revealing that AlNFsub.3 and AlPFsub.3 are both metals in nature. From the density of states, the support of various electronic states in the band structures are explained. Other various optical characteristics have been calculated from the investigations of the band gap energy of the aforementioned compounds. These compounds absorb a significant amount of energy at high levels. At low energy levels, the compound AlNFsub.3 is transparent to incoming photons, whereas the compound AlPFsub.3 is somewhat opaque. The examination of the visual details led us to the deduction that the compounds AlNFsub.3 and AlPFsub.3 may be used in making ultraviolet devices based on high frequency. This computational effort is being made for the first time in order to investigate the aforementioned properties of these chemicals, which have yet to be confirmed experimentally.
The weak adsorption of COsub.2 and the fast recombination of photogenerated charges harshly restrain the photocatalytic COsub.2 reduction efficiency. The simultaneous catalyst design with strong ...COsub.2 capture ability and fast charge separation efficiency is challenging. Herein, taking advantage of the metastable characteristic of oxygen vacancy, amorphous defect Bisub.2Osub.2COsub.3 (named BOsub.vC) was built on the surface of defect-rich BiOBr (named BOsub.vB) through an in situ surface reconstruction progress, in which the COsub.3 sup.2− in solution reacted with the generated Bisup.(3−x)+ around the oxygen vacancies. The in situ formed BOsub.vC is tightly in contact with the BOsub.vB and can prevent the further destruction of the oxygen vacancy sites essential for COsub.2 adsorption and visible light utilization. Additionally, the superficial BOsub.vC associated with the internal BOsub.vB forms a typical heterojunction promoting the interface carriers' separation. Finally, the in situ formation of BOsub.vC boosted the BOvB and showed better activity in the photocatalytic reduction of COsub.2 into CO (three times compared to that of pristine BiOBr). This work provides a comprehensive solution for governing defects chemistry and heterojunction design, as well as gives an in-depth understanding of the function of vacancies in COsub.2 reduction.
PDF
