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Different schemes for passivation of solar cells fabricated using casted multicrystalline silicon from Eurosolare are investigated. The efficiency of solar cells with front side oxide surface passivation, front side and/or back side hydrogen plasma passivation are compared. It is shown that oxide passivation of the front surface combined with hydrogen passivation from the back side is the optimum passivation scheme. A 16.2% top efficiency is obtained on 4 cm2 cells implementing this passivation scheme and a 16.8% top efficiency is estimated with an optimized ARC combination.

In order to verify the convenience of employing low cost feedstock for realizing high performance polycrystalline material for solar cells, two different studies were undertaken; first, the possible influence of B-P compensation and microstructure on minority carrier diffusion lengths and, second, the presence of B-O deep centres and their dependence on impurity concentration were investigated. Experimental results show that material with excellent features, approaching those of single crystal, is produced with the directional solidification method, using both compensated and uncompensated feedstock, thus indicating that grain boundaries and other extended defects have little or negligible influence on minority carrier lifetime. Results in CZ material show the presence of a dopant dependent recombination centre related to oxygen content, of still unknown nature which needs closer investigation.

The III–V compounds deposited as thin films on variuos substrates are a new perspective in the terrestrial photovoltaic energy conversion. The single crystal solar cells based on such compounds show, indeed, a conversion efficiency higher than silicon solar cells. Unfortunately these compounds are too expensive to be used as bulk materials in the flat solar modules. Taking advantage of their high absorption coefficients, many approaches have been recently attempted for growing polycrystalline thin films of InP, GaAsP and especially GaAs on low cost substrates such as graphite, alumina and refractory materials. It was also demonstrated that a structure GaAs/Ge/Si may have the necessary features in terms of both efficiency and cost to compare these devices with single crystal silicon cells. The potential economical and technical advantages of the III–V thin film solar cells are illustrated together with the relative technology. Present activities in many laboratories are also described. In particular some recent results, obtained at ASSORENI Laboratories on GaAs/Ge/Si solar cells, are discussed. Finally the future potentiality of the photoemissive solar cells is mentioned.

The photovoltaic properties of n‐CdS/p‐Si heterojunctions prepared by vacuum deposition of CdS:In on single‐crystal silicon substrates are reported. Power conversion efficiencies of 9.5% (cell area 1.5 cm2) have been obtained. The I‐V characteristics and their temperature dependance suggest tunneling as the dominant conduction mechanism.

One of the most promising trends in device development foressen for the near future is the incorporation of multilayer structures in all devices in which performance improvements justify the higher technological costs. In this perspective, the most diffused epitaxial technologies, which are Liquid Phase Epitaxy (LPE), Vapour Phase Epitaxy (VPE), Pyrolysis of Organometallic Compounds (OMP) and Molecular Beam Epitaxy (MBE), are discussed with respect to a number of definite problems. These topics are related to: 1) Interfaces; 2) Composition profiles; 3) Doping profiles and 4) Stoichiometry. Although the present review refers mainly to the III–V compounds and alloys, some attention has been paid to outlining the general aspects of the above problems. Moreover some comments are made on the possible developments and industrial impact of the epitaxial technologies.

The use of the 19F(γ, n)18F, 27Al(γ, x)24Na, 197Au(γ, n)196Au, and 12C(γ, x)7Be reactions as absolute monitors for high-energy, high-intensity bremsstrahlung beams is discussed. The cross sections per equivalent quantum and the absolute cross sections, in the energy range 300–1000 MeV, are reported for these reactions. 19F(γ, n)18F, 27Al(γ, x)24Na, and 12C(γ, x)7Be reactions are proposed as very simple and suitable systems for monitoring purposes.

The (γ, n) cross sections per equivalent quantum of 12C, 103Rh, 127I, 197Au and 238U have been measured with a bremsstrahlung beam of maximum energies in the range 1–5.5 GeV. Within the experimental errors of the activation method, no contribution of photons above 1 GeV was found. This result disagrees with some previous measurements at energies below 1 GeV but agrees with the predicted values obtained from simple theoretical estimates.

GaAs1−xPx was grown by pulling from Ga-rich solutions using the liquid encapsulation method. X-ray analysis and optical measurements performed on the first grown portion of the crystal give a value x=0.3. Electrical measurements showed that the crystal is n-type with carrier concentration N = ∼ 1017 cm−3 and Hall mobilities μH = ∼ 500 cm2 V−1 sec−1 at room temperature.

Note: Cnr,lab elettr stato solido,grp nazl strutt mat,via cineto romano 42,00156 rome,italy. ISI Document Delivery No.: T0156 Reference LSE-ARTICLE-1974-001 Record created on 2006-10-03, modified on 2017-05-12