Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Electrical and Computer Engineering

First Advisor

Vikram Dalal


Amorphous silicon solar cells have been extensively studied. However, it is found that the properties of a-Si:H solar cells degrade upon light illumination, and this limits their application. Recently, it has been shown that this instability is correlated with the presence of SiH2 bonds, and a technique, namely chemical annealing, was suggested to improve the stability of a-Si:H. Although a number of results have been reported, no chemical annealed devices with good quality were reported;In this work, chemical annealing technique was studied to improve the stability of a-Si:H solar cells. It is found that when the annealing was done in hydrogen plasma, the films remained amorphous; in contrast, when in helium plasma, and the annealing time is equal or more than 20 seconds, the films became crystalline. These unusual results show that it is not necessary to have a high hydrogen dilution to obtain nanocrystalline films, and contradict the generally accepted assumption that high hydrogen dilutions are needed to crystallize the amorphous films based on the reactive etching of H ions. Instead, it might be the case that not only the reactive etching effect from the H ions, but also the ion bombardment play a role in crystallizing the amorphous films.



Digital Repository @ Iowa State University,

Copyright Owner

Nanlin Wang



Proquest ID


File Format


File Size

101 pages