With currently available materials, thermocouples are expensive and have low efficiency.
Semiconductor materials produce many volts per degree K, but only operate below about 125C. The best I have seen are les than 5-7% efficient. Compare this with 15 – 20% for a thermoacoustic engine.

The requirement for a thermocouple is high electrical conductivity with a low thermal conductivity. Unfortunately, above 125C thermocouples are currently metallic based. These tend to have matching thermal and electrical conductivity.
 
The manufacturing of thermocouples is relatively high tech, so most of the device would have to be imported to the developing country.
 
Although thermoacoustic technology is less efficient than a diesel engine, its life is much greater as it has virtually no moving parts (just the linear alternator to generate electricity). TA engines can operate on many different fuels such as wood, dung and solar. TA engines can be manufactured at a low-capability manufacturing site thus bringing business opportunities to the local community.