Electrode CdSe single crystal

Table I. CdSe Single Crystal Electrode Characterization...

The importance of controlling the operating temperatures of single-crystal and polycrystalline n-CdSe/polysulfide/CoS liquid junction cells to obtain the maximum possible photoconversion has been emphasized [55], In fact, a dramatic effect of temperature was established on the power output of the cells, particularly those based on thin film electrodes. 

It has been illustrated that polycrystalline materials can be operated in regenerative electrolytic solar cells yielding substantial fractions of the respectable energy conversion efficiency obtained by using single crystals. Pressure-sintered electrodes of CdSe subsequently doped with Cd vapor have presented solar conversion efficiencies approaching 3/4 of those exhibited by single-crystal CdSe electrodes in alkaline polysulfide PEC [84]. 

Differences in behavior between polycrystalline and single-crystal CdSe electrodes in polysulfide PEC involving the short- and long-term changes in photovoltage and photocurrents have been discussed by Cahen et al. [88], on the basis of XPS studies, which verified the occurrence of S/Se substitution in these electrodes when immersed in polysulfide solution, especially under illumination. The presence of a thin (several nanometers) layer of CdS on top of the CdSe was shown to influence... 

In this paper the calculated I-V characteristics using a model that includes depletion region recombination (2J are compared with experimental results for single-crystal CdSe electrode/polysulfide electrolyte junctions. In particular the predicted effects of redox ion concentration and light intensity on the I-V characteristics are analyzed and compared with experimental data. 

Here we will consider mainly the short-circuit current (SCC) output stability characteristics of both small grain, thin film CdSe and Cd(Se,Te)-based PEC s as well as those of single crystal CdSe-based cells, wh are different crystal faces are exposed to the solution, after they have undergone any of a series of surface treatments. These studies show a strong dependence of the output stability on solution composition, on real electrode surface area, on surface treatment, on crystal face and on crystal structure (for the Cd(Se,Te) alloys) (1,2 7). 

Etching. The polycrystalline electrodes were etched, before use in polysulfide solution, in 3% HNO3 in cone. HC1 for secs. Single crystal CdSe electrodes were polished, before use, down to... 

For comparison, figure 3B shows results not only for the relatively most stable face of a single crystal (2) and a polycrystalline thin layer prepared by pasting 5), but also for a pressed pellet of CdSe (2). This last electrode shows stability behaviour intermediate between that of the two other electrodes. This behaviour is evident also in the decrease in output stability, which is less steep than that of the single crystal electrode. 

D. V. Talapin, E. V. Shevchenko, C. B. Murray, A. Kornowski, S. Forster, and H. Weller. Cdse and CdSe/CdS nanorod solids. J. Am. Cherrt Soc., 126 12984-12988, 2004 M. Adachi, Y. Murata, J. Takao, J. T. Jiu, M. Sakamoto, and F. M. Wang. Highly efficient dye-sensitized solar cells with a titania thin-film electrode composed of a network structure of single-crystal-hke Ti02 nanowires made by the oriented attachment mechanism. J. Am. Chem. Soc., 126 14943-14949,2004... 

Nanocrystalline particulate films, which exhibit pronounced quantum size effects in three dimensions, are of great interest due to applications in solar cell (108-112) and sensor (57, 113-115) applications. They exhibit novel properties due to not only the SQE manifested by individual nanoparticles but also the total surface area. Unlike MBE and MOCVD methods used to prepare quantum well electrodes, these electrodes can be prepared by conventional chemical routes described in Section 9.5.2.2. For example, II-VI semiconductor particulate films were prepared by using low concentrations of precursors and by controlling the temperature of the deposition bath. Nodes demonstrated the SQE for CdSe thin films deposited by an electroless method (98). The blue shift in the spectra of CdSe films has been demonstrated to be a function of bath temperature. As described in Section 9.5.2.1, electrodeposition of semiconductors in non-aqueous solvents leads to the formation of size-quantized semiconductor particles. On a single-crystal substrate, electrodeposition methods result in epitaxial growth (116, 117), and danonstrate quantum well properties. 

Fig. 17.10 Schafer et al.14 have observed single mode lasing from core shell CdSe/ZnS nano crystal quantum dots in a glycerine water mixture. The fluorescence spectrum (black line) showed clear peaks of WGM and single mode lasing (grey line) was observed for sufficiently small droplets ( 10 pm) and high pump laser intensities (53 mJ crrT2 in 10 ns pulses at 532 nm). Insert shows the droplet trapped between the electrodes. Reprinted from Ref. 14 with permission. 2008 American Chemical Society...

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