Charging Capacitor with Solar Panel
Even for the simplest schematics, simple resistor is not enough. You definitely want a series diode to prevent capacitor discharging INTO solar panel when it is dark, as well as some way to prevent capacitor from being overcharged -- either zener, red/yellow LED, or a shunt regulator. In fact, once you have a protection circuit you no longer need a resistor divider -- just charge at max power and let regulator dissipate any extra power. This gives the following schematics:


http://www.edn.com/design/power-management/4422103/Fast-charging-a-supercapacitor-from-energy-harvesters

"OVP" may be:


a 1W, 2.0 V zener (zeners generally have high voltage tolerances)
1W red/yellow LED
2 regular diodes in series (each has about 0.7v-1v voltage drop, two would regulate to 1.5-2V)
diode + transistor shunt regulator