Poor Photovoltaic Performance Research Articles

Properties of amorphous silicon solar cells fabricated from SiH 2Cl 2

Chlorinated intrinsic amorphous silicon films [a-Si:H(Cl)] and solar cell i-layers were fabricated using electron cyclotron resonance-assisted chemical vapor deposition (ECR-CVD) and SiH 2Cl 2 source gas. n–i–p solar cells deposited on ZnO–coated SnO 2 substrates had poor photovoltaic performances despite the good electronic properties measured on the a-Si:H(Cl) films. Improved open–circuit voltage ( V oc) of 0.84 V and fill factor (FF) of 54% were observed in n–i–p solar cells by providing an n/i buffer layer and by using Ga-doped ZnO coated glass substrates. However, the FF improvement was still rather poor, which is thought to originate from high interface recombination in the ECR deposited solar cells. The V oc and the FF showed much stable feature against light soaking.

Effects of oxidized layers on built-in potentials in ITO/InP solar cells

The degradation of indium phosphide at high temperatures invariably results in poor photovoltaic device performance. In an attempt to limit the severe effects of heating, a layered device structure was fabricated which resulted in markedly improved devices over simple one layer structures. Not only were device efficiencies improved, but also the unique structure of these devices brought the possibility of an oxide layer being part of the much-debated ITO/InP structure. It is proposed that the junction is a homojunction enhanced by the presence of an insulating layer.

Ternary chalcogenide-based photoelectrochemical cells III. n-CuIn 5S 8/aqueous polysulfide

The photoelectrochemistry of the spinel phase CuIn 5S 8 in polysulfide electrolyte was studied. A sequence of annealing in S and in vacuum was found to give optimal material for this purpose. The performance of such material could be improved by acid etching and photoelectrochemical etching; both of these treatments deplete the top layer of Cu. Notwithstanding obvious kinetic limitations in polysulfide, the title system shows a negative temperature dependence. The output stability which is inferior to that of n-CuInS 2 systems in polysulfide, is limited by increasing dark currents. These may be due to the formation of CuS on the surface. While, for all examples studied, the indirect bandgap around 1.3 eV was observed, the direct gap around 1.5 eV was seen clearly only for photoelectrochemically etched electrodes. It is suggested that the poor photovoltaic performance and mediocre output stability behaviour of CuIn 5S 8 photoanodes is related to the inability of the material to tolerate significant Cu depletion and to the absence of a homogeneous indium oxide surface layer. This latter finding may be connected with the fact that most of the indium is octahedrally, rather than tetrahedrally coordinated, in contrast to what is the case for the chalcopyrite type disulfide.

Low-cost solar cells based on large-area unconventional silicon

Low-cost approaches to solar cell manufacture require the use of inexpensive low-grade nonsingle crystalline silicon. Earlier experimental results indicate that conventional polysilicon, as it is used as ingot for the single crystal growing process, leads to solar cells of poor photovoltaic performance. These problems were overcome by utilizing unconventional nonsingle crystalline silicon, which is characterized by controlled size and structure of the individual grains. With modified processing, optimized in respect to the unique structure of the material, large-area solar cells could be realized under production scheme methods. Cells exhibiting dimensions up to 11 cm × 11 cm were fabricated, AM0 efficiencies of 8 percent could be achieved corresponding to AM1 values exceeding 10 percent. On test samples of 2 cm × 2 cm area AM0 efficiency Of 12.5 percent (AM1 value equivalent 14.0 percent) could be reached. The new material together with the optimized processes offer potentials for significant cost reduction by virtue of their being applicable to volume production and to automated fabrication techniques.