Impact of the injection‐level‐dependent lifetime on V_oc, FF, ideality m, J₀₂, and the dim light response in a commercial PERC cell

Abstract

The injection‐level‐dependent (ILD) lifetime of the silicon wafer impacts many characteristics of the final photovoltaic cell. While efficiency is commonly understood to be impacted by the silicon bulk lifetime (at the maximum power point injection level), this work demonstrates the wide ranging impacts of ILD lifetime on the Voc, the fill factor (FF), the diode ideality factor m, and the dim light response. Instead of a two‐diode model, we utilize a boundary + ILD bulk lifetime model to analyze a commercial passivated emitter rear contact (PERC) cell featuring an AlOx dielectric rear passivation. The ILD lifetime is directly measured and used to calculate the bulk recombination current across injection levels. With this boundary + ILD lifetime model, we demonstrate the role of the ILD lifetime on many cell parameters in this PERC cell. For most high efficiency commercial p‐type monocrystalline solar cells, the typically lower bulk lifetime at the maximum power point versus the lifetime at the open circuit point reduces the measured FF and pseudo‐FF. This work illustrates that for a commercial PERC cell with AlOx rear passivation, the ILD lifetime is the primary mechanism behind reduced FF, ideality factors greater than 1, and the source of the J02 term in the two‐diode model. The crucial implications of this work are not only to better understand commercial PERC cell loss mechanisms but also to encourage a focus on different metrics in cell diagnostics. One such metric is the Voc at 0.1 or 0.05 suns. Copyright © 2016 John Wiley & Sons, Ltd.

Recombination Parameters of the Diffusion Region and Depletion Region for Crystalline Silicon Solar Cells under Different Injection Levels

“…Specifically, when the injection level increases from 900 W/m 2 to 1200 W/m 2 , the J 02 of a PERC solar cell increases from 2.94 × 10 −9 A/cm 2 to 9.86 × 10 −9 A/cm 2 , but the J 02 of an Al-BSF solar cell increases rapidly from 9.12 × 10 −9 A/cm 2 to 2.77 × 10 −8 A/cm 2 . The obtained result agrees with other publications [47,48].…”

“…A/cm 2 . The obtained result agrees with other publications [47,48]. Figure 7, it is found that both the J01/J02 ratio of the Al-BSF solar cell and the J01/J02 ratio of the PERC solar cell increase with the decreasing injection level.…”

Elucidating potential‐induced degradation in bifacial PERC silicon photovoltaic modules

“…With more positive charges accumulating in the AlO x /SiN x stack, minority‐carrier electrons are attracted to the surface (ie, a depletion region along the rear surface), whereby they can easily recombine with the majority‐carrier holes at the surface; this, in turn, will lead to further losses in P mpp , V oc , and I sc (Figure B). As for the change in FF when PID‐p progresses, several factors could have played a role, such as the uncertainty of the measurements, FF loss due to an increase in recombination, changing in FF loss due to series resistance effects and the injection‐level dependence of the bulk lifetime and the rear surface recombination velocity …”

Effect of MACE Parameters on Electrical and Optical Properties of ALD Passivated Black Silicon

“…4a shows the effective minority charge carrier recombination lifetime of the same samples that have b-Si on both sides at an injection level of 10 15 cm -3 , which is a typical condition under one sun illumination. The figure reveals that all samples have an effective carrier lifetime on the order of hundreds of µs even without polishing, which is sufficiently high for >20 %-efficient PERC solar cells [31]- [33].…”