Why smartphones still don't work from solar panels

At the MWC 2025 exhibition, the Chinese company Infinix showed an unusual prototype: a smartphone with the back panel almost entirely covered with solar cells. The approximate power output is about 2 W under ideal conditions. This seems like a great idea, since even the most durable smartphones can last only a few days without recharging. Despite this, we have not seen a massive launch of models with a built-in solar panel among Android devices.

Android Police writes about why this haven't happened yet.

What's the problem with solar power?

While solar panels are able to harvest energy from a free and accessible source — the sun — they have a number of limitations. The technologies available today convert about a quarter of the light into electricity. That's about 240 watts per square meter, but for the size of a smartphone, that's only a few watts. The Infinix Concept gets up to 2 watts in maximum light. Given the standard 5000 mAh battery, the device needs at least 9 hours of direct sunlight (straight directed) to fully charge.

Moreover, the solar panel only provides noticeable benefits in direct sunlight. Indoors or in the shade, the performance drops to almost zero. Even the angle at which the sunlight hits the panel is important - it's enough to change the slope slightly and the efficiency drops sharply.

Why a panel on the back is problematic

If a manufacturer wants to build a solar panel into a smartphone, they have to sacrifice a few things. First, you have to make room: either make the device thicker or install a smaller battery. Wireless charging will also be unavailable because the solar panel will take up space. In addition, the cover will block light from the panel, rendering it useless, and exposed solar cells are quite fragile, reducing their resistance to damage.

In addition, the heat from direct sunlight is harmful to the battery. High temperatures accelerate the wear and tear of lithium-ion batteries, so leaving your phone in the blazing sun is a direct way to shorten the life of your device.

There have been attempts in the past to make phones that could be charged by the sun. Nokia offered an optional solar panel for the 1610/1611 back in 1997, and Samsung and LG also made several devices with built-in solar cells. However, they didn't get a follow-up, which indicates low demand. Buyers expected more autonomy, but instead got a few minutes of talk time from an hour of charging in the bright sun.

Will solar panels on smartphones be useful in the future?

Solar energy has long proven its effectiveness in a variety of areas, but for smartphones, current technologies have not yet met expectations. There are too many compromises against the background of a very modest increase in autonomy. Instead, manufacturers are actively developing batteries with increased capacity, and chargers are becoming more powerful.

New battery designs allow for a capacity of more than 6000 mAh to be packed into a relatively thin body. In addition, external batteries (power banks) remain an alternative solution — they are inexpensive, compact, and can quickly help out when needed.

So for now, the idea of smartphones with built-in solar panels is only attractive as a prototype. Perhaps in the future, technologies will emerge that can change the situation, but for now, compromises and low efficiency outweigh the benefits.

As a reminder, power banks have long been an indispensable gadget for those who are often away from the outlet. There are many models on the market, the characteristics of which differ significantly, and sometimes even have nothing to do with reality.

We also wrote that some smartphones are capable of charging other devices and accessories thanks to the reverse charging feature. Many Android devices have been supporting this technology for a long time, and recently it started appearing in the latest iPhone models.