See, for example, the paper "Transition metal oxides - Thermoelectric properties" (Walia S., Balendhran S., Nili H. et. al) // Progress in Materials Science. 2013. V. 58. P. 1443-1489, and references in it.

Seebeck coefficient is defined as a measure of thermal emf produced due to per degree change of temperature across a junction of two dissimilar metals.

The thermal emf only and solely depends on the temperature and not on the other parameters like dimensions of the material/metals.

I am more working on Seebeck coefficient of metals than semi-conductors.

To my knowledge mainly semiconductors are used as TEG materials (perhaps some "intermetallic semiconductors")

People working on TEG characterize the efficiency by a global coefficient ZT (Z times T in Kelvin). Z is proportional to the square of the absolute Seebeck coefficient (it produces energy). It is also proportionnal to the electrical conductivity (you must not loose the energy produced by Joule effect) and inversely proportionnal to the thermal conductivity (if the thermal conductivity is too high you reduce the temperature difference thus the energy produced by Seebeck effect)

You musf find the properties entering in Z for Cu2O, for exemple in google scholar (http://scholar.google.com/) or find review articles on thermoelectricity where list of meritus factor. I found several answers on scholar google with the keywords: ZT seebeck Cu2O

Sorry for having not be able to answer directly to your question.

 Thank you Prof Gasser. Cu2O peaked my interest because it is a natural semiconductor material and I've seen several articles which state that a Cu- Cu2O junction has a large Seebeck Coefficient. The biggest drawback is that Cu2O acts as an insulator at temperatures around 30-200Celsius hence ZT value would not be high. Metals on the other hand are much more user friendly though efficiency is limited and I've been testing some TEGs with some basic metals. So alloys are the way forward.   

If you are interested by metallic alloys, may I recommend you to have a look on intermetallic semi-conductors. I was impressed by a paper of Romaka who elaborated such alloys and Fruchart who gave a physical understanding ( Journal of Alloys and Compounds 438 (2007) 8–14 ).

From an industrial point of view high temperature are more promising that low temperatures. These alloys may work at high temperatures to transform energy of waste into electricity.

Regards.