LeTID mitigation via an adapted firing process in p‐type PERC cells from SMART cast‐monocrystalline, Czochralski and high‐performance multicrystalline silicon

Abstract

In this work, we analyse passivated emitter and rear cells (PERC), based on wafers made from seed manipulation for artificially controlled defects technique (SMART) monocrystalline silicon, magnetically grown and conventional Czochralski (mCz and Cz) silicon, and high‐performance multicrystalline (hpm) silicon. All wafers were processed identically except for the hpm wafers, which received an acidic texture instead of random pyramids. The energy conversion efficiency η of the SMART cells of 21.4 % is similar to the mCz cells (21.5 %) while being more than 1.90.1em%abs higher than for the hpm cells. Furthermore, we here show for the first time that light‐ and elevated temperature‐induced degradation (LeTID) is mitigated in hpm, Cz and SMART PERC cells without significant losses in initial efficiency by an adapted fast‐firing process, incorporating slower firing ramps that can be used in industrial production. The cells that are fired with these ramps show no significant efficiency loss ( 10.1em%rel<normalΔη<20.1em%rel) during LeTID testing at 75°C and 0.15 suns illumination for 1100 h, while the reference fast‐firing process results in efficiency losses of 50.1em%rel<normalΔη<60.1em%rel due to LeTID. For Cz cells that have been treated to regenerate the boron–oxygen defect prior to LeTID testing, the maximum degradation was reduced from normalΔη≈30.1em%rel to normalΔη≈1.50.1em%rel.

The Impact of Different Hydrogen Configurations on Light- and Elevated-Temperature- Induced Degradation

“…The extent of LeTID can be manipulated by different factors, like the peak temperature of the firing step [15], [24], the cooling ramp of the firing step [12], [25], different preannealing steps [26], [27], [28], but also sample properties like the composition of the silicon nitride layer [7], [29], [30], interlayers such as aluminum oxide (Al 2 O 3 ) [31], [32], or the thickness of a sample [13], [33]. It was shown that the initial hydrogen concentration correlates with the peak firing temperature [34], besides other factors like the composition of the hydrogen-containing dielectric surface layers [35], or interlayers such as Al 2 O 3 [32], [36].…”

Light and elevated temperature induced degradation and recovery of gallium-doped Czochralski-silicon solar cells

“…Both, the set-peak temperature (i.e., 810 °C) and the band velocity (6 m min −1 ) of the firing furnace were lower in the present study, than in our previous study (850 °C, 6.8 m min −1 ). Whereas the lower firing peak temperature would result in less hydrogen diffusing into the silicon bulk, a slower cooling ramp has also been shown to have significant impact on the extent of degradation 29 . Another difference is the sample structure with poly-Si on the back of our lifetime sample instead of a symmetrical stack of AlO x and SiN y .…”

Annual trends of indoor output measurement results from photovoltaic modules exposed outdoors in Tosu city, Japan

“…In the case of PERC, LID and LETID were mainly analyzed by using small size cells. 24,[28][29][30][31][32][33] Comparing with these reports and outdoor exposed cell and module data will give us a better knowledge and understanding. Outdoor exposure tests of these four kinds of PERC modules will also be continued in the future.…”