Herein, boron‐doped cast‐monocrystalline silicon wafers that have been fabricated using the Seed Manipulation for ARtificially controlled defect Technique (SMART mono‐Si) are examined. Their suitability for passivated emitter and rear cell (PERC) fabrication is investigated. Applying a zero busbar layout energy conversion efficiencies of η = 21.9% for SMART mono‐Si, η = 22.2% for gallium‐doped Cz‐Si (Cz‐Si:Ga), and η = 22.3% for boron‐doped Cz‐Si (Cz‐Si:B) are achieved at similar doping levels between 0.7 Ω cm ≤ ρB ≤ 1.0 Ω cm. Therefore, SMART mono‐Si PERCs show almost the same performance as Cz‐Si PERCs. Apart from the performance of SMART mono‐Si PERCs, the minority charge carrier bulk lifetime τB of the SMART mono‐Si wafers after different high‐temperature process steps in the PERC process flow is investigated. After emitter formation, this analysis confirms the high material quality of SMART mono‐Si yielding τB ≈ 1.3 ms at an injection level of Δn = 1015 cm−3. The bulk lifetime after firing is similar to the level determined for mCz‐Si:B and Cz‐Si:Ga reference wafers of similar doping level.

We propose a method of three-dimensional (3D) visualization of growth interfaces in crystalline ingots prepared by directional solidification and apply the method to cast silicon ingot for solar cells. The method consists of dispersing inclusions along with the growth interface by insertion of a quartz rod followed by measuring inclusions distribution by an infrared brick inspection system. Then, inclusions distribution can be visualized in 3D, which allows extracting growth interfaces as planes. By fitting the plane with a simple polynomial expression, its macroscopic shape and local gradient can be estimated. The method yields us the local changes in growth interfaces and thus contributes to the development of the crystal growth method for high-quality ingots.

The use of cast-mono technology to control the development of structural defects during the block casting process enables the crystallization of Silicon for solar cells with good material quality at high throughput and low cost. The obstacles, ingrowth of parasitic grains and development of dislocation clusters, might be overcome by the SMART seeding technique, i.e. the introduction of functional defects. Ingots with the cast-mono and SMART seeding configuration, as well as a new approach including a monocrystalline spacer have been crystallized. Whereas the ingrowth of parasitic grains was reproduced with the standard cast-mono technique, the functional defects suppressed the ingrowth of parasitic grains until an ingot height of approx. 80 mm. By the introduction of an additional monocrystalline spacer, the ingrowth of parasitic grains could be avoided for the whole ingot height of 210 mm. The spreading of dislocation clusters in the monocrystalline area could be reduced significantly using the SMART approach in contrast to the standard cast-mono configuration. This reduction of structural defects enabled high bulk lifetimes above 1 ms on large wafer areas for both pand n-type material after typical high efficiency solar cell processing steps.