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Abstract Morphology control is critical to achieve high efficiency CH3NH3PbI3 perovskite solar cells (PSC). In this paper, fluorinated perylene diimide (FPDI) was used as novel organic electron transport material in planar heterojunction perovskite solar cells. The perovskite film was fabricated by sequential vacuum vapor deposition, and the film morphology could be controlled by optimizing the FPDI film morphology with short time solvent spin-coating or solvent vapor annealing (SVA). Dense and uniform perovskite film with high substrate coverage could be obtained when the FPDI film was treated by chloroform SVA for half an hour, and the fill factor (FF) of the perovskite solar cell increased from 30.44% to 55.20%, enhancing the power conversion efficiency (PCE) from 3.23% to 7.44%. The PCE of the best device reached 7.93%, which was comparable to that (8.25%) of the conventional ZnO electron transport layer based perovskite device prepared by the same method.

Copper indium diselenide (CuInSe2) compound was synthesized by reacting its constituent’s elements copper, indium and selenium in near stoichiometric proportions (i.e. 1:1:2 with 5% excess selenium) in an evacuated quartz ampoule. Synthesized pulverized compound material was used as an evaporant material to deposit thin films of CuInSe2 onto organically cleaned sodalime glass substrates, held at different temperatures (300–573 K), by means of single source thermal evaporation method. The phase structure and the composition of chemical constituents present in the synthesized compound and thin films have been investigated using X-ray diffraction and energy dispersive X-ray analysis, respectively. The investigations show that CuInSe2 thin films grown above 423 K are single phase, having preferred orientation of grains along the (112) direction, and having near stoichiometric composition of elements. The surface morphology of CuInSe2 films, deposited at different substrate temperatures, has been studied using the atomic force microscopy to estimate its surface roughness. An analysis of the transmission spectra of CuInSe2 films, recorded in the wavelength range of 500–1500 nm, revealed that the optical absorption coefficient and the energy band gap for CuInSe2 films, deposited at different substrate temperatures, are ∼104 cm−1 and 1.01–1.06 eV, respectively. The transmission spectrum was analyzed using iterative method to calculate the refractive index and the extinction coefficient of CuInSe2 thin film deposited at 523 K. The Hall effect measurements and the temperature dependence of the electrical conductivity of CuInSe2 thin films, deposited at different substrate temperatures, revealed that the films had electrical resistivity in the range of 0.15–20 ohm cm, and the activation energy 82–42 meV, both being influenced by the substrate temperature.

Abstract Bifacial solar cells that can generate electricity from either front or rear side are regarded as advanced photovoltaics for markedly increased photoelectric conversion efficiency. We present here the fabrication of transparent RuSe counter electrodes by an alternating electrodeposition method for bifacial dye-sensitized solar cells (DSSCs). The catalytic and photovoltaics performances are maximized by tuning stoichiometric Ru/Se ratio and bilayer number. Upon irradiation by AM1.5 (100 mW cm−2), the device yields a maximized front efficiency of 8.72% and a rear efficiency of 5.9%, arising from the >80%-transparency of RuSe electrode in visible light region. This strategy provides new opportunities for fabricating high-performance DSSCs.

Abstract In flat-plate PV/T systems, there are some contradictions in the temperature requirements for the heat and electricity acquisition. The widely-used crystalline-silicon solar cells are negatively affected by the high temperature inside the PV/T collector. This paper proposes to use temperature-insensitive solar cells in PV/T and the CdTe used has the advantages of low power temperature coefficient, high photovoltaic efficiency, and low costs. Besides, the sandwich structure that CdTe cells are sealed between two pieces of glass can prevent them from the permeating of moist air. The CdTe-PV/T is experimentally tested and compared with a Poly-Si-PV/T system and it exhibits better instantaneous electrical performance at high operating temperatures and gains more electrical energy throughout the day. Then the influence of cells’ coverage ratio is investigated experimentally and the result shows that a higher coverage ratio is beneficial to the electrical and energy-saving performance. Furthermore, a new quasi-steady-state mathematical model is established and verified. Parametric discussions are conducted for performance optimization. The black TPT coating with higher emissivity performs better than the selective absorption coating of the absorbing plate, contrary to the traditional PV/T collector. The heat transfer mode between the back glass and the absorbing plate is different in different thicknesses of the air gap. Reducing the thickness can effectively improve the system’s performance in terms of thermal, electrical, and temperature. Then an improved CdTe-PV/T eliminating the backglass and air gap is proposed and numerically simulated. This research hopes to provide some ideas for the applicant and the optimization of CdTe-PV/T in hot climates.

Abstract The desalination of water is a process wherein the brackish water is purified by removing the salts. With increasing demand for fresh water, there is a vast scope for development of sea water desalination process. A number of methods exist for the desalination process, but solar desalination method promises to save energy in today’s energy crunch scenario. A novel solar desalination setup is proposed here. It uses an elliptic hyperboloid concentrator and a helical receiver along with a multi-tray desalination unit to purify water in the most effective manner. The helical receiver proposed in the present work aims at the Dean Flow effect in order to enhance heat transfer in laminar flow. The effectiveness of this property with respect to various physical parameters has been observed and an optimum design has been suggested based on this. The elliptic hyperboloid concentrator is a special design for concentrating solar radiation because of it offers to operate at high efficiency without the requirement of tracking. A detailed ray-tracing code was developed to simulate the radiation incident on the concentrator and an accurate estimation of the optical efficiency was made based on this. The two systems were integrated in order to arrive at a maximum output level for the solar desalination system as a whole.

Abstract The stable Ni(OH)2 ultrafine nanosheet combined with Bi2MoO6 to form heterojunction have been fabricated successfully by a simple and mild one-step solvent-thermal method. In this work, the Ni(OH)2/Bi2MoO6heterojunction increased the absorption range of visible light compared to the pure Bi2MoO6, from the UV–visible diffuse reflectance spectrum (DRS), thus greatly improving the degradation rate of organic dyes. The Ni(OH)2/Bi2MoO6heterojunctionwith different proportions was prepared by a mild one-step solvothermal method by controlling the mass fraction ratio between the nickel source and the bismuth source. The morphology and structure of the heterojunction materials were characterized by afield emission scanning electron microscopy (SEM) and a field-emission high-resolution transmission electron microscope (TEM). In this experiment, the photocatalytic properties were demonstrated by the degradation of organic dye Rhodamine B by the prepared samples. The results showed that 2%Ni(OH)2/Bi2MoO6 composite had the strongest photocatalytic performance and the maximum degradation rate was about 98% (135 min) when the Rhodamine B was degraded by visible light irradiation. It also can be found that Bi2MoO6composited by Ni(OH)2ultrafine nanosheet, compared with pure Bi2MoO6, the photocatalytic performance is improved by decreasing the recombination rate of photogenic carriers.

Abstract Significant efforts have been made to improve the performance of the Cu(In1-xGax)Se2 (CIGS) solar cells by tuning the band gap of the CIGS absorber to match it with the solar spectrum. However, the performance of the current record-holding CIGS solar cells is still far from theoretical expectations. Various researchers reported that the open circuit voltage (Voc) and the fill factor (FF) degrade in wide band gap CIGS solar cells. However, the limiting factors on further boosting the efficiency are still a matter of debate. In this study, we focus on tuning the properties of the interfacial layer between the rear contact and the wide-gap CIGS absorber to lower the contact resistance and recombination rate. Based on the numerical simulation using SCAPS (a solar cell capacitance simulator), we find that a MoO3 interfacial layer with high work function is more effective than its MoSe2 counterpart in reducing the back barrier, which in turn increases the Voc and the FF of the solar cell. We further predict that an overall efficiency of 24% can be achieved by reducing the back surface recombination and Schottky barrier with sub-micrometer a thick CIGS absorber. This work puts forward a strategy to improve the efficiency of wide band gap CIGS solar cells whilst reducing the raw materials consumption.

Abstract The J–V equation of an illuminated solar cell is implicit and recently it is shown that this equation can be expressed explicitly using rational function considering pade approximants. Here an explicit model for J–V characteristic is proposed using equivalent rational function form having two shape parameters. This model allows a simple closed form estimation of maximum power point voltage. The proposed explicit model is validated using wide variety of solar cells.