handphone solar charger

please help me...
i want to build a solar charger for handphone..
my problem is i dant know how to build it, and what component i must use..
now, i have a solar panel, 4v... but the batery is only 3.7v..
is that i must reduce the voltage?

There are cell phones that some people call "mobile phones".
I have wireless phones at home.
I have never heard about a phone that is called a "handphone".
Maybe you are in a foreign country and you speeky zee a foreign language?

If it is a cell phone then the charger circuit is inside the phone. The power supply is just a 5V supply that feeds the charger circuit in the phone.
The 5V charger charges the lithium battery to +4.2V. Since your solar panel is only 3.7V and needs a diode (0.7V) to stop the battery from discharging into the solar panel then it won't work.

thanks for the reply...
its all about a mobile phone...
i want to create a mobile phone charger used solar power..
now, i have bought a 5v solar panel..
so, do i have put a diod?.. it is because the mobile phone only 3.7v....

All you have to do is copy the voltage and current from the AC to DC adapter. It has a diode that stops the battery from discharging into the solar panel in the dark. A 3.7V lithium battery charges to 4.2V so the voltage from your solar panel is too low.

oh...
thanks...

why not use a buck/boost converter or just a boost converter depending on the voltage your solar panel generates? You can get simple converters in pre-constructed packages so only a few components are needed