  We introduce a concept of semi-shunts representing needle shaped metallic
protrusions shorter than the distance between a device electrodes. Due to the
lightening rod type of field enhancement, they induce strong electron emission.
We consider the corresponding signature effects in photovoltaic applications;
they are: low open circuit voltages and exponentially strong random device
leakiness. Comparing the proposed theory with our data for CdTe based solar
cells, we conclude that stress can stimulate semi-shunts' growth making them
shunting failure precursors. In the meantime, controllable semi-shunts can play
a positive role mitigating the back field effects in photovoltaics.
