Heterojunction cell

Anodization generally results in the formation of films with limited thickness, uncertain composition, defects, and small crystallite size. Thus, the barrier nature of the n-type semiconducting CdS film obtained in the previous manner makes it too thin to form the basis of Cu2S/CdS or CdTe/CdS solar cells by the normal dipping process. Heterojunction cells of low efficiency have, however, been made by anodization followed by vacuum deposition of the added layer (CU2S). 

The cathodic approach has been investigated actively as a method for the production of thin film CdS, in particular for the fabrication of heterojunction cells. Photoactive CdS films could be grown in alkaline NH3/NH4Cl-buffered aqueous solutions containing thiosulfate as sulfur source and complexed Cd (EDTA+NH3), on Ti substrates [41]. The electroreduction of thiosulfate was considered to proceed as... 

Optimum conditions for the formation of CdS by the acidic method on metallic A1 substrate at 25 °C have been reported as follows pH 2.3, potential -1 V vs. SCE, and electrolysis time > 2 h [44]. Thermal treatment improved the characteristics of the films and their photovoltaic properties, which were evaluated by evaporating a CU2S layer on the CdS/Al film, to form a heterojunction cell. The influence of the deposition substrate on the formation and morphology of CdS was found to be important. The aluminum substrates gave the best results among Pt, Mo, and Al. In the case of molybdenum, surface blocking by adsorbed sulfur was considered. 

Duffy NW, Lane DW, Ozsan ME, Peter LM, Rogers KD, Wang RL (2000) Structural and spectroscopic studies of CdS/CdTe heterojunction cells fabricated by electrodeposition. Thin Sohd Films 361 314-320... 

Although conventional solar cells based on silicon are produced from abundant raw materials, the high-temperature fabrication routes to single-crystal and polycrystalline silicon are energy intensive and expensive. The search for alternative solar cells has therefore focused on thin films composed of amorphous silicon and on other semiconductor heterojunction cells (e.g., cadmium telluride and copper indium... 

Photovoltaic Devices with OPV4—Ceo- The increased lifetime of the charge-separated state, which extends into the millisecond time domain, opens the possibility of using the OPVrt-Coo dyads as the active material in a photovoltaic device. As an important difference with previous bulk heterojunction cells, the covalent linkage between donor and acceptor in these molecular dyads restricts the dimensions of the phase separation between the oligomer and the fullerene that could freely occur in blends of the individual components. This can be considered as a primitive attempt to obtain more ordered and better-defined phase-separated D-A networks. 

Measurements of the temperature dependent current-voltage (J-V) characteristics of p a-SiC H/n c-Si heterojunction solar cells with different doping levels in the p a-SiC H layer have been made, and it is reported that as long as the p a-SiC H layer in these heterojunction cells is highly doped, collection problems do not occur under normal operating conditions. In some related work by the same authors, a study has been reported of the current-voltage... 

Figure 1.5 Typical organic photovoltaic cell architectures, (a) Bilayer cell (b) bulk heterojunction cell.

It is in principle possible to determine the energy diagram for the whole heterojunction cell in this way. Indeed Mahrov et al. (2004) have recently carried out photo-... 

Figure 6.20 Spectral quantum collection efficiency in a CdTe /Xi02 heterojunction cell for various bias voltages. The solid hues give a best fit to the experimental data, based on a minority-carrier diffusion length of 130 nm (Ernst, 2001).

Figure 6.26 Spectral quantum efficiency spectra for CdTe/Ti02 heterojunction cells on planar and microporous T102 substrates at short-circuit conditions.

Furthermore phase separation of Ceo and CuPe is deseribed at elevated temperatures [55] whieh affeets the moleeular arrangement, but ean not be de-teeted by the teehniques used here. Altogether, film morphology and strueture of blends of flat CuPe and spherieal Ceo moleeules are still not very well understood and need further investigation. This will beeome partieularly important in photovoltaic cells, where this material combination is a potentially promising candidate for so-called buUc-heterojunction cells [21, 56],... 

Dye-Sensitized Cells Dye-sensitized solar cells (DSSCs) are slightly more complex than bilayer and bulk heterojunction cells, but as was the case for bilayer cells, the increase in device complexity reduces the number of functions that must be performed by each of the materials. A schematic drawing of a dye-sensitized solar cell is shown in Fig. 8.8. A layer of sintered, interconnected TiC>2 nanoparticles, which serves as the electron transport material (ETM), is coated by a thin layer of light absorbing dye. The remaining pores in the dye-coated TiC>2 layer are then filled with a... 

Typical representatives of this class of homojunction semiconductors are Si several III-V compounds, most prominently GaAs and from the class of ITVI compounds CdTe, since it can be doped p- and ra-type, while others cannot. Several ternary compounds are also used, most prominendy CuInSe2 and similar ternaries. An example for a heterojunction cell is the CdS/CdTe combination (Meyers and Birkmire, 1995). For more details see Green (2001). 

Dark Current of CuPctC o Planar-Mixed Heterojunction Cells... 

Dye-sensitized solar cells (DSCs) are a paricularty successful example of a bulk heterojunction cell architecture. A wide bandgap inorganic semiconductor (typically a metal oxide) is sensitized to the solar spectrum by attaching a surface-adsorbed... 

The cell ITO/CdS/SAlPc/Au was reported, where SAlPc is a surfactant aluminium Pc (41) It was made by sequential electrodeposition of CdS and SAlPc thin films onto ITO. The electrodeposited CdS acts as a blocking contact and all the band bendings occur in the SAlPc. A heterojunction cell was formed between n-CdS and p-type Pcs such as H2PC, ZnPc, MgPc, CuPc, MnPc, PbPc and VOPc The cell ITO/ CdS/Pc/Au was fabricated by electrodeposition of a CdS thin film and sequential vacuum deposition of Pc and Au. V = 0.54 V, — 285 pA cm" and conversion efficiency of 0.10% were obtained for the ITO/CdS/ZnPe/Au cell. 

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