Abstract-In recent years, high-performance multicrystalline silicon (HPMC-Si) has emerged as an attractive alternative to traditional ingot-based multicrystalline silicon (mc-Si), with a similar cost structure but improved cell performance. Herein, we evaluate the gettering response of traditional mc-Si and HPMC-Si. Microanalytical techniques demonstrate that HPMC-Si and mc-Si share similar lifetime-limiting defect types but have different relative concentrations and distributions. HPMC-Si shows a substantial lifetime improvement after P-gettering compared with mc-Si, chiefly because of lower area fraction of dislocation-rich clusters. In both materials, the dislocation clusters and grain boundaries were associated with relatively higher interstitial iron point-defect concentrations after diffusion, which is suggestive of dissolving metal-impurity precipitates. The relatively fewer dislocation clusters in HPMC-Si are shown to exhibit similar characteristics to those found in mc-Si. Given similar governing principles, a proxy to determine relative recombination activity of dislocation clusters developed for mc-Si is successfully transferred to HPMC-Si. The lifetime in the remainder of HPMC-Si material is found to be limited by grain-boundary recombination. To reduce the recombination activity of grain boundaries in HPMC-Si, coordinated impurity control during growth, gettering, and passivation must be developed.

The current paper investigates the structure of low-lifetime areas observed in a < 110 >-oriented mono-like silicon ingot grown from monocrystalline seeds. These areas are related to dislocation clusters forming at seed junctions and several generation mechanisms are discussed. Dislocations generated due to physical contact between seeds could only be completely avoided by introducing gaps between the seeds. Large gaps were, however, found to suffer from alternative generation processes not found in small gaps. Dislocations generated in the seeds and in peripheral grains does not necessarily move in to the main crystal and low-lifetime areas are mainly related to dislocations generated above the seeding structure. Dislocations are found to form clusters aligning along < 111 >-directions and are proposed to happen by glide on {111}-planes from the boundary plane between two seed crystals. The extent of low-lifetime areas and corresponding dislocation clusters, for junctions containing no or small gaps, appear to mainly depend on the misorientation between seeds and by attaining sufficiently low misorientation the high bulk lifetime can be retained also at the junctions. Analysis of the misorientations along principal axes indicates that larger misorientations can be tolerated if the misorientation is limited to a single tilt axis

No abstract

Phone: þ47 92029610 $43% for the entire PV industry and 47%/37% for mono/ multi-Si respectively. However between 2010 and 2015, the period which has conclusively moved photovoltaics from a niche product to a cost efficient energy supply alternative in an increasing amount of markets, the CAGR of mono-Si has decreased to 18% while multi-Si remains above 40%.In contrast to mono-, multi-Si is by necessity a compromise: The generation of extended crystal defects cannot be eliminated. The ingots are made in square, thick walled crucibles, and using high purity quartz as in crucibles

No abstract

No abstract

We report on studies of sub‐bandgap defect related photoluminescence (DRL) signals originating from radiative recombination through traps in the bandgap of cooled mono‐like silicon wafers. Spectrally resolved photoluminescence (SPL) and multivariate curve resolution (MCR) have been used in combination, to study the behaviour of sub‐bandgap photoluminescence (PL) emissions in wafers cut from different heights in a pilot‐scale mono‐like silicon ingot. No DRL signals were found in the main mono‐like body. Strong defect related sub‐bandgap emissions correlating with heavily dislocated areas, are found directly above some of the seed junctions. The DRL signal exhibits a correlation with the number of axis with small angle misalignment in the junctions of the seeds. The signal conventionally labelled D1 (0.80 eV) decreases with ingot height. A mechanism relating this signal to oxygen is proposed. The signals D3 (0.94 eV) and D4 (1.00 eV) are found to co‐occur, supporting previous studies, and similarly to the D2 (0.87 eV) signal, their strength is found to increase with ingot height. As the content of the transition metal impurities in the ingot is supposed to increase with height, this supports a reported link between the D3 and D4 signals with Fe, as well as a link between D2 and other impurities. An emission previously found in multicrystalline material and labelled D07 (0.70 eV), is found to solely exist as the only DRL signal recorded by us in parasitic crystals, growing into the main mono‐like ingot from the crucible walls. This contradicts the common notion that the D1–D4 signals are strongly related to, and always follow dislocations. Total photoluminescence spectrum (right) and distribution (left) of the PL signal with centre energy 0.70 eV emanating from the parasitic crystals growing into the bulk mono‐like Si crystal from the crucible walls.

The nucleation mechanism for directional solidification of multicrystalline silicon (mc‐Si) in silicon nitride (Si3N4) coated crucibles has been investigated. A combination of thermal and particle size analysis was used to show that the nucleation undercooling was inversely proportional to the particles size. The particle size was increased by keeping the silicon melted for increasing time periods and the growing particles were identified as β‐Si3N4. The results from the particle analysis were verified by topographical studies using scanning electron microscopy (SEM). These results indicate that β‐Si3N4 particles are the dominant nucleation substrates for mc‐Si in Si3N4 coated crucibles. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)