New Product: ‘Silexium’ coating from Sixtron reduces light-induced degradation of c-Si solar cel

• 
  Sixtron Advanced Materials

Product Briefing Outline: Sixtron Advanced Materials has introduced a patent-pending antireflective passivation coating technology that it says will greatly reduce the light-induced degradation (LID) problem for crystalline-silicon solar cells. The company claims to have demonstrated an 88% reduction in LID on cells treated with its silane-free ‘Silexium’ coating. The Silexium films can be used with high-performance mono-crystalline boron doped p-type Cz (Czochralski) silicon solar cells without the use of silane gas.

Problem: Solar cells fabricated with boron doped p-type Cz wafers suffer from performance degradation when exposed to light illumination. They become 3 to 5 % (rel.) less efficient when first exposed to the sun. Within hours, small amounts of oxygen in boron-doped monocrystalline solar cells (resulting in B-O complex) react with sunlight to decrease the solar cell's output efficiency.

Solution: Silexium films have been demonstrated to effectively passivate these boron-oxygen (B-O) complexes which are responsible for LID under illumination. In this way, LID can be significantly reduced to less than 2 % rel., typically 1% rel., thereby increasing stabilized (post-LID) solar cell efficiency. Under the proper process conditions, Silexium films can provide the following key benefits: Comparable end-of-line cell efficiency of SiH4-free SiCxNy to pyrophoric SiNx for front-side n+ emitter passivation and ARC (anti-reflection coating); significantly less LID with excellent stability. Higher shunt resistance and lower reverse leakage current. With rear-side p-type silicon surface passivation, PECVD SiO2/SiCxNy stack has better cell efficiency than PECVD SiO2/SiNx stack for PERC-type cell.

Applications: Flexibility of various passivation coatings from a single source; SiC, SiCN, SiCO, SiCON etc, for both front-side and rear-side passivation

Platform: The precursor for Silexium films is delivered to industry standard plasma enhanced chemical vapor deposition (PECVD) equipment by Sixtron's SunBox silane-free gas generation system.

Availability: January 2010 onwards.