High-efficiency solar cells on edge-defined film-fed grown (18.2%) and string ribbon (17.8%) silicon by rapid thermal processing

Abstract

Solar cell efficiencies of 18.2 and 17.8% were achieved on edge-defined film-fed grown and string ribbon multicrystalline silicon, respectively. Improved understanding and hydrogenation of defects in ribbon materials contributed to the significant increase in bulk lifetime from 1–5 μs to as high as 90–100 μs during cell processing. It was found that SiNx-induced defect hydrogenation in these ribbon materials takes place within one second at 740–750 °C. The bulk lifetime decreases at annealing temperatures above 750 °C or annealing times above one second due to the enhanced dissociation of the hydrogenated defects coupled with the decrease in hydrogen supply from the SiNx film deposited by plasma enhanced chemical vapor deposition.

Fundamental Research and Development for Improved Crystalline Silicon Solar Cells: Final Subcontract Report, March 2002 - July 2006

“…This is probably because the glass frit in paste B was able to dissolve a lot more Ag at the higher temperature and became highly supersaturated, producing large precipitates or crystallites at the interface upon cooling. This is also consistent with the Ag-Pb phase diagram [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The Ag SIMS profiles in Figure 5-11 clearly show that pastes A and B failed because of Ag-induced junction shunting while PV168 survived 835°C firing because of the significantly reduced penetration of Ag into the 100 Ω/sq emitter.…”

“…The τ eff is composed of radiative, non-radiative, and surface recombinations and in general, dominated by non-radiative recombination in Si. In a 22 simple case neglecting a diffusion of the photo-generated minority carriers, the I BB and I Def can be expressed as following [2-4]:…”

“…All the bulk lifetime measurements in Figure 4-1 shows that the phosphorus diffusion enhances the light-soaked lifetime significantly. This is attributed to 1) impurity gettering by phosphorus diffusion [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] and 2) the reduction of metastable defects (responsible for LID) by high-temperature treatment. For this reason, the lifetime in the finished cell correlates better with the post-diffusion lifetime rather than the as-grown lifetime.…”

“…For this reason, the lifetime in the finished cell correlates better with the post-diffusion lifetime rather than the as-grown lifetime. To consider the effectiveness of the high temperature process in the reduction of LID, it is useful to first calculate the normalized metastable defect concentration, defined as [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. This can be calculated from the lifetime in annealed and light-soaked states as follows: N t * was calculated using eq.…”

Concentration and penetration depth of H introduced into crystalline Si by hydrogenation methods used to fabricate solar cells

“…Several samples that had been hydrogenated by a furnace anneal or RTP were analyzed in this way to determine the penetration depth of H. 30,45 The concentration of PtH 0 complexes for the sample whose spectra are shown in Fig. 3 20,24 Furthermore, an anneal of a few seconds at temperatures near 800°C is consistent with typical belt furnace anneals used by industry. 46 Here, we have examined SiN x / Si: Pt samples annealed for 1 and 10 s. 47 Figure 4 shows that the areal density of H introduced by these brief anneals is comparable to that shown in Fig.…”