OK, your first image shows a Red and Black wire, two wires off the solar panel. A Google of "USB Pinout" will bring up a few dozen images. Your cable shows a USB A (Large) and USB mini or micro which likely is where it connects to your phone. Note the connector pinout and where the power pins are (the outermost) on a standard USB A connector. If you cut off the connector end which connected to your panel note the pins. The cable may even use the same red and black color scheme. You are only using two of the four wires.
Ron