Step 3: And here comes the solar panel
To connect the solar cells in series, I connect successively the bottom side of a cell to the top side of the other. Solar cells are not that good a conductor. To aid the current flow, bus bar, the more conductive white region on the solar cell, is printed onto the cells. That is why you can see that I am only applying the conductive ink onto the bus bar. After applying 2 dots of instant glue onto the cell edge and a dot of conductive ink onto the edge of the bus bar, I placed the second solar cell onto the first with a 1mm overlapping. Repeat this for 5 more times and you will get a panel consists of 7 cells. Note that the more you overlap, the less of the cell is exposed to sunlight and thus the less current you can get from the cell.
Before I put the panel onto my paper house, I measured its current under a light just to see if all connections are good. My panel gives 80 something mA when not shaded by my fingers but you can still see 57.6 mA when I took the photo with my other hand.
Don't worry too much if the current reads zero. It may only be caused by a bad connection or two. If this happens, identify the bad connection with an aid of a multimeter and use a hot air gun to soften that connection. Then, pull the connected cells apart and redo that connection. You may also simply do another panel from the beginning instead, if you prefer so.