Unisolar panels have bypass diodes across every cell, so you only lose the output from that one cell if it is shaded. Amorphous panels ads I have seen have always touted a much better tolerance to shade. I had always assumed that all amorphous silicon panels were made this way, I haven't checked. The drawback with these panels is that they are less efficient. On another thread I did a comparison, IIRC amorphous requires 1.5-2 times the area to produce the same power.
Solar Online Australia - UniSolar 64W Solar Panel US64 12V Amorphous Solar Module
"Bypass diodes are connected across each cell, allowing the modules to produce power even when partially shaded."
I did come across an ad recently that said their new process makes bypass diodes obsolete and increases efficiency, I believe that this was an amorphous panel.
link I posted earlier bothered me because it seemed inconsistent about power loss. So doing more research
from this link below I learned that you need at least 1 bypass diode per about 15 cells in series to prevent damage to the panel.
(Nice animations too)
Looking at this Kyocera
Figure 7 you see there are two sets of bypass diodes. The positive of one set is connected to the negative of the second set and are also connected to what they call the "dummy (non electric)" terminals. I can't see any reason why you need two diode drops for the bypass, but if you assume that the middle of the series connection of the cells of the panel is brought out to a terminal, and that terminal is the dummy terminal, then the one of each of the two sets of diodes are each protecting 18 cells or half of the panel. Going back to the link I posted earlier and now assuming the panel has one bypass diode for each half.
Kyocera | Products | Kyocera Solar Energy | Understanding Solar | Modules
This explains why shading one full cell only reduces the output by half, only half of the cells in the panel are bypassed. It also explains why they show the panel output going to zero when the bottom row is blocked as you have blocked cells in each of the two halves.
Electronics - Solar Power Wiring
All large modules have been designed for multiple series connections to accommodate a bypass
diode every 18 cells. This is the principal reason for the dual voltage four terminal output found
on all BP Solar (Solarex) large power modules. The voltage built up across 18 cells is insufficient
to damage a cell even under extreme conditions of temperature and shadowing. Using larger
numbers of cells between diodes allows for substantially more voltage to build up creating more
heat and possibly resulting in module failure under worst case conditions.
So what I had learned before about there being a single
bypass diode for a crystalline panel appear to have been either obsolete or incorrect. Instead of losing an entire panel due to shading a cell you will only lose half the panel on a 36 cell module.