> The 4 legged 'transistor' is an IC that I could not find any info about online, but I have used them for some projects. If you wire them like the solar light, they take the solar panel current to charge the battery (1.5v). When the solar panel current drops off enough because of lack of light it then provides the battery's current to the LED. There seems to be a built in joule thief inside too, outputting enough voltage to drive a white LED from a single 1.5v cell. It's a pretty cool little part. I have one running a bi-core blinking eye bot that I made for my 3 year old son... he calls it his night night bot. As I recall, there is an inductor you have to wire with it as well. I drew up a wiring schematic of it some time ago, I'll see if I can dig it up, but otherwise just wire it like it is set up in the solar light and replace the white LED with your circuit.
I've already looked them up, and Piotter was right,they are bridge rectifiers. The solar lights I have actually use an LDR to measure light levels, but I plan on replacing these with NPNs, with the base wired to an Nv input, through the rectifier to the solar cell. Now that I think about it, that would actually qualify as a type 3 SE, which are my favorite of coarse.