pretty common questions asked, try searching the forums for transistors and you will find alot of results
basically it is about how thermionic devices (valves) were used in communications in telephones, due to its numerous faults it required for a replacement, at the same time the three scientists were also researching for replacements and came across some past invention which led to the invension of the transistor, not really detailed but covers the basic idea
in this point you need to talk about what were the disadvantage of thermionic devices which lead to their shortcomings, what materials were potential to transistors and relate to its properties, as well as the advantages of transistors which became such a important discovery with a significant impact on the society
talk about silicon, germanium and how doping improves the conductivity, p type and n type as well
as for the history best to research, i remember the first transistor used germanium called the point contact transistor as it was from the German radar or something, then junction transistors and now field-effect transistors
