Improvement of electron diffusion lengths in polycrystalline silicon wafers by aluminium
In order to improve the electron diffusion lei wafers, an aluminium layer was deposited on the back sul 2 h. It was found that Ln is increased, provided the initi; density of dislocations is larger than 5 x 104 cm-2. Backsig to explain the results and it is assumed that dissolved c
Potential improvement of polysilicon solar cells by grain boundary and intragrain diffusion of aluminum
Experimental results are presented that imply potential improvements afforded by aluminum diffusion in both bulk and thin‐film polysilicon solar cells. For bulk cells, a high‐temperature aluminum diffusion (alloying) is shown to increase the minority‐carrier diffusion length by gettering intragrain impurities. The role of the grain boundaries in this process and the influence of a light bias on the carrier lifetime are discussed. For thin‐film cells, a low‐temperature aluminum diffusion is shown to substantially passivate grain boundaries and hence decrease the recombination velocity. The decrease is evaluated using electron‐beam‐induced‐current (EBIC) measurements interpreted via numerical analysis of the underlying carrier‐transport problem. The actual benefit of the grain‐boundary passivation to the open‐circuit voltage of a thin‐film cell is discussed.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.