Permanent battery in cellphones - solar panel

The simplest answer could be, current technology of photovoltaic cells aren't capable enough to do that.

The amount of electrical energy that could be generated from ambient light is in fact quite low for a solar panel the size of a cell phone. Even if the panel is placed directly in sunlight it may not generate enough energy to meet the phone's intense energy requirements. Even if, some how, the panel can meet the energy requirements, without a battery the phone will prove to be unusable at night!

lal

The simplest answer could be, current technology of photovoltaic cells aren't capable enough to do that.

The amount of electrical energy that could be generated from ambient light is in fact quite low for a solar panel the size of a cell phone. Even if the panel is placed directly in sunlight it may not generate enough energy to meet the phone's intense energy requirements. Even if, some how, the panel can meet the energy requirements, without a battery the phone will prove to be unusable at night!

A bit unrelated, I've been to hiking recently and had hired a night lamp. It was quite bright, LED I suppose. It had the provision of charging via solar. We had kept it on charge around 4 pm and it was charging in the slightest of light. There was an LED glowing indicating its being charged. I was quite surprised the 2"x2" panel in dim sunlight was able to glow the LED. May be it had charged well too. Not sure on that front.

I have seen that on many power banks too. There would be a solar panel and even in the shadows, the charging led will be blinking. Clear indication that those photovoltaic cells are working, generating quite enough power for that smd led to glow. That is a real good thing about LEDs right, even only a fraction of the rated current makes it glow, although may be not to its maximum brightness.

The kind of efficiency current PV cells have is not very promising to be used as portable chargers. A lot of factors limit it, including the availability of enough light. And even the 'portable' factor might need to be overlooked to generate decent power by using multiple inter-connected PV arrays.