High-Performance and Traditional Multicrystalline Silicon: Comparing Gettering Responses and Lifetime-Limiting Defects

Abstract

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.

Light‐induced degradation in quasi‐monocrystalline silicon PERC solar cells: Indications on involvement of copper

“…The apparent absence of Cu‐LID in the Cz‐PERC is explained by the above result that dislocations present in the qm‐PERC increase the recombination activity of Cu‐LID. Dislocated materials are also known to exhibit weaker gettering efficiency than dislocation‐free materials , which may leave higher concentrations of Cu and other transition metals in the bulk after emitter formation. The possibility that several different defects can play a role is an important consideration in studies related to LID and its mitigation in PERC devices.…”

Grain boundary effect on lifetime in high performance multicrystalline silicon during solar cell processing

“…While conventional mc-Si suffers from dislocations multiplicating in relatively large grains, HPMC-Si is characterized by reduced grain size and more random angle grain boundaries, on which dislocations annihilate. These different defect distributions result in different behaviour upon solar cell processing [12]. This work investigates this behaviour in industrially processed wafers.…”

Recombination Strength of Dislocations in High‐Performance Multicrystalline/Quasi‐Mono Hybrid Wafers During Solar Cell Processing

“…However, in HPMC, random angle grain boundaries offset some of their own recombination activity by annihilating dislocations . This leads to increased performance in HPMC cells, when compared with the standard multicrystalline cells that contain higher densities of efficiency‐limiting dislocations …”

“…Even though gettering and hydrogenation are applied in standard solar cell manufacturing, the HPMC‐Si material is still limited in efficiency by defects, particularly by dislocations . The effect of dislocations on the recombination of minority charge carriers was modeled by Donolato with a parameter describing the recombination strength γ d , normalized to a dimensionless parameter Γ = γ d / D , where D is the minority carrier diffusion coefficient .…”