Copper, indium, and gallium chalcogenide nanocrystals (binary, ternary, and quaternary) have been used to fabricate high-efficiency thin-film solar cells. These solution-based methods are being ...scaled-up and may serve as the basis for the next generation of low-cost solar cells. However, the formation pathway to reach stoichiometric ternary CuInSe2 or any chalcopyrite phase ternary or quaternary nanocrystal in the system has not been investigated but may be of significant importance to improving nanocrystal growth and discovering new methods of synthesis. Here, we present the results of X-ray diffraction, electron microscopy, compositional analysis, IR absorption, and mass spectrometry that reveal insights into the formation pathway of CuInSe2 nanocrystals. Starting with CuCl, InCl3, and elemental Se all dissolved in oleylamine, the overall reaction that yields CuInSe2 involves the chlorination of the hydrocarbon groups of the solvent. Further, we show that the amine and alkene functional groups in oleylamine are not necessary for the formation of CuInSe2 nanocrystals by conducting successful syntheses in 1-octadecene and octadecane. Hence, the role of oleylamine is not limited to nanocrystal size and morphology control; it also acts as a reactant in the formation pathway. Typically, the formation of copper selenide (CuSe) and indium selenide (InSe) nanocrystals precedes the formation of CuInSe2 nanocrystals in oleylamine. But it was also found that Cu2–x Se (0 < x < 0.5) and In2Se3 were the primary intermediates involved in the formation of CISe in a purely non-coordinating solvent such as 1-octadecene, which points to the surface-stabilization effect of the coordinating solvent on the less thermodynamically stable indium selenide (InSe) nanocrystals. We also show that the yield of the chalcopyrite phase of CuInSe2 (as opposed to the sphalerite phase) can be increased by reacting CuSe nanocrystals with InCl3.
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The creation of a suitable inorganic colloidal nanocrystal ink for use in a scalable coating process is a key step in the development of low-cost solar cells. Here, we present a facile solution ...synthesis of chalcopyrite CuInSe2 nanocrystals and demonstrate that inks based on these nanocrystals can be used to create simple solar cells, with our first cells exhibiting an efficiency of 3.2% under AM1.5 illumination. We also report the first solution synthesis of uniform hexagonal shaped single crystals CuInSe2 nanorings by altering the synthesis parameter.
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Several non-vacuum based approaches have been employed to deposit the Cu(In,Ga)Se2 layer in photovoltaic devices, but most of them use processing temperatures in the vicinity of 500°C. Here, we ...present the results on a facile solution-based deposition technique for CuInSe2 (CISe) and CuIn(S,Se)2 (CISSe) thin films with deposition temperatures of 300°C. CuxSe (1.5≤x≤2) or CuyS (1≤y≤2) precursor films deposited on a substrate were reacted with InCl3 and Se reactants in oleylamine to form CISe or CISSe thin films of the desired thickness, composition and crystal structure. Solar cells processed from these films on Mo-coated glass substrates demonstrated an efficiency of 2% under AM 1.5 illumination. We also present external quantum efficiency and capacitance–voltage measurements from these devices providing insights into the device performance.
► We present a solution-based deposition technique for CuInSe2 films at 300°C. ► Lower temperatures, same number of steps enable processing on flexible substrates. ► Solar cells demonstrate an efficiency of 2%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The development of suitable colloidal nanocrystal inks are a key step in the development of low-cost solar cells since they enable the use of fast and inexpensive coating processes such as spray ...coating and roll coating to form a thin film photo-absorbing layer. Copper indium selenide (CISe) nanocrystals were synthesized from CuCl, InCl3 and elemental selenium via a simple batch reaction in a coordinating solvent. The use of these nanocrystals for solar cells has been demonstrated by fabricating devices, with the first solar cells having an efficiency of 2.8%. Insights into the formation pathway of these nanocrystals are a key step to gain a better control over their electronic properties. Upon investigations, it was found that the formation of CISe nanocrystals in oleylamine solvent (cis-1-amino-9-octadecene) is preceded by the formation of copper selenide (CuSe) and indium selenide (InSe). The reaction takes place via the chlorination of the hydrocarbon (-CH, -CH2 & -CH 3) groups in oleylamine. In support of the proposed formation pathway, CISe nanocrystals have been synthesized in solvents without any amine or alkene groups, e.g. octadecane. Also, it was found that the reaction between the binary selenides, CuSe and InSe, primarily resulted in the formation of the disordered sphalerite phase of CISe. However, the liquid-solid phase reaction between InCl3 and CuSe in the presence of Se increased the yield of the ordered chalcopyrite phase. The knowledge of the formation pathway, where CuSe (or CuS films deposited on a substrate) reacts with InCl3 and Se in oleylamine to form CISe, has been used to develop a chemical liquid deposition (CLD) technique which enables the deposition of CISe thin films directly on to a substrate from a solution of precursors. This technique enables the fabrication of solar cells on low-cost, easy-to-install, flexible polymeric substrates by circumventing the high temperature (500 Celsius) vapor-phase processing steps. The use of these CLD-based films for applications in solar cells has been demonstrated by fabricating Glass/Mo/CuInSe2/CdS/i-ZnO/ITO/Ag devices of 2% efficiency. Based on the advantages of the CLD technique, a solution-selenization technique was also developed which facilitates the reaction between any deposited film and selenium in the liquid phase at temperatures in the vicinity of 300 Celsius. CuInS2 films deposited on flexible molybdenum foil substrates were reacted with selenium in oleylamine to form CuIn(S,Se)2 thin films of the desired thickness. Our first solar cells processed from these films demonstrated an efficiency of 2.85%.
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8.
Electrochemical Hydrogen Production He, Ting; Kar, Mahaprasad; McDaniel, Neal D. ...
Springer Handbook of Electrochemical Energy
Book Chapter
The electrochemical–photoelectrochemical production of hydrogen has been widely investigated for decades, largely driven by the potential to reduce environmental impact, satisfy distributed demand, ...and enhance public perception. As an alternative to steam methane reforming for hydrogen production, these approaches have enjoyed renewed vigor over the last several years. This chapter reviews recent progress in low-temperature electrolysis, high-temperature electrolysis, and photoelectrochemical techniques. Perspectives are given on the electricity consumption, carbon dioxide emission, costs of hydrogen production, and competitive landscape in the future hydrogen market.
