Energy requirement for the production of silicon solar arrays

An assessment of potential changes and alternative technologies which could impact the photovoltaic manufacturing process is presented. Topics discussed include: a multiple wire saw, ribbon growth techniques, silicon casting, and a computer model for a large-scale solar power plant. Emphasis is placed on reducing the energy demands of the manufacturing process

Coplanar back contacts for thin silicon solar cells

The type of coplanar back contact solar cell described was constructed with interdigitated n(+) and p(+) type regions on the back of the cell, such that both contacts are made on the back with no metallization grid on the front. This cell construction has several potential advantages over conventional cells for space use namely, convenience of interconnects, lower operating temperatures and higher efficiency due to the elimination of grid shadowing. However, the processing is more complex, and the cell is inherently more radiation sensitive. The latter problem can be reduced substantially by making the cells very thin (approximately 50 micrometers). Two types of interdigitated back contact cells are possible, the types being dependent on the character of the front surface. The front surface field cell has a front surface region that is of the same conductivity type as the bulk but is more heavily doped. This creates an electric field at the surface which repels the minority carriers. The tandem junction cell has a front surface region of a conductivity type that is opposite to that of the bulk. The junction thus created floats to open circuit voltage on illumination and injects carriers into the bulk which then can be collected at the rear junction. For space use, the front surface field cell is potentially more radiation resistant than the tandem junction cell because the flow of minority carriers (electrons) into the bulk will be less sensitive to the production of recombination centers, particularly in the space charge region at the front surface

Universal Short-time Behaviour of the Dynamic Fully Frustrated XY Model

With Monte Carlo methods we investigate the dynamic relaxation of the fully frustrated XY model in two dimensions below or at the Kosterlitz-Thouless phase transition temperature. Special attention is drawn to the sublattice structure of the dynamic evolution. Short-time scaling behaviour is found and universality is confirmed. The critical exponent $\theta$ is measured for different temperature and with different algorithms.Comment: 18 pages, LaTeX, 8 ps-figure

Anomalous finite-size effect in superconducting Josephson junction arrays

We report large-scale simulations of the resistively-shunted Josephson junction array in strip geometry. As the strip width increases, the voltage first decreases following the dynamic scaling ansatz proposed by Minnhagen {\it et al.} [Phys. Rev. Lett. {\bf 74}, 3672 (1995)], and then rises towards the asymptotic value predicted by Ambegaokar {\it et al.} [Phys. Rev. Lett. {\bf 40}, 783 (1978)]. The nonmonotonic size-dependence is attributed to shortened life time of free vortices in narrow strips, and points to the danger of single-scale analysis applied to a charge-neutral superfluid state.Comment: 4 pages, 2 figure

Critical Exponents of the Fully Frustrated 2-D Xy Model

We present a detailed study of the critical properties of the 2-D XY model with maximal frustration in a square lattice. We use extensive Monte Carlo simulations to study the thermodynamics of the spin and chiral degrees of freedom, concentrating on their correlation functions. The gauge invariant spin-spin correlation functions are calculated close to the critical point for lattice sizes up to $240\times 240$; the chiral correlation functions are studied on lattices up to $96\times 96$. We find that the critical exponents of the spin phase transition are $\nu=0.3069$, and $\eta=0.1915$, which are to be compared with the unfrustrated XY model exponents $\nu=1/2$ and $\eta=0.25$. We also find that the critical exponents of the chiral transition are $\nu_{\chi}=0.875$, $2\beta=0.1936$, $2\gamma= 1.82$, and $2\gamma\>\prime=1.025$, which are different from the expected 2-D Ising critical exponents. The spin-phase transition occurs at $T_{U(1)}=0.446$ which is about 7\% above the estimated chiral critical temperature $T_{Z_{2}}= 0.4206$. However, because of the size of the statistical errors, it is difficult to decide with certainty whether the transitions occur at the same or at slightly different temperatures. Finally, the jump in the helicity modulus in the fully frustrated system is found to be about 23\% below the unfrustrated universal value. The most important consequence of these results is that the fully frustrated XY model appears to be in a novel universality class. Recent successful comparisons of some of these results with experimental data are also briefly discussed. (TO APPEAR IN PRB)Comment: 47 pages (PHYZZX

Phase 2 of the array automated assembly task for the low cost silicon solar array project. Interim report

The LSA Automated Array Assembly Task has as its goal the manufacture of photovoltaic modules at a capacity of 500 MW per year at a cost of $0.50 per peak watt. Divided between ten solar cell manufacturers, each installation should produce 50 MW per year. This implies that automated machinery would continuously produce 120 solar cells per minute. The purpose of this report is to detail the processes and techniques which are believed to have great promise of accomplishing this task. The initial stages of the program were involved in studying the possibility of automated assembly. Phase 1 reviewed a large cross section of processes, conceptual designs, and innovative technologies in preparation for 1986. Through this documentation, a large amount of comprehensive data has been collected. It is these reports upon which the next phase of the program is based. The purpose of Phase 2 is to propose an automated sequence, verify it and present future cost projections. Utilizing the large amount of information available from Phase 1 and drawing from its own experience Solarex has proposed a process sequence which it is believed has great potential of achieving the LSA goals. This report describes the processes, details, the verification tests performed, and estimates the cost of such an automated array assembly