Why smartphones don't have solar panels? 

As we know smartphones are so smart why can't they have to add a solar panel to recharge. 

In 2009 SAMSUNG released the world's first solar powered cell phone.It is known as the Samsung guru E1107 and featured a solar cell built into its black plate.When exposed to sunlight,the cell generated electricity which in turn recharged the phones battery. 

As if a solar panel is set to mobile phone it may cause a fire with the heat generated from the solar panel. 

Also the mobile manufacturers got a doubt where to install the solar panel.

You would got a doubt "what about solar powered calculators".

Solar powered calculators only take a tiny amount of power as compared to charge a mobile with solar panels.

There are many problems to set a solar panel to recharge your mobile phone. So mobile manufacturers didn't giving out those types of smartphones.