Emerging Thin-Film Technologies for IoT

October 04, 2022 by Darshil Patel

Various thin-film technologies may revolutionize photovoltaic systems for portable electronic devices.

The photovoltaic industry has witnessed several new improvements, making the manufacturing processes cheaper and increasing power conversion efficiency. Thin-film solar cells are considered the future of solar technology as they present several advantages, such as higher efficiency indoor energy harvesting, simpler manufacturing, lower costs, and less ecological impact than conventional photovoltaic (PV) cells.

In addition, modern portable applications are emerging, in which conventional solar cells are unsuitable due to their bulk, rigidity, and weight. Thin-film PVs are significantly lighter and suitable for applications where flexibility and less weight are required.

Thin-film solar modules can be integrated within smoke alarms, motion sensors, smaller electronic displays, and other small form-factor gadgets to eliminate batteries or external wiring. This advantage makes them more environmentally friendly. These cells are also suitable for building facades or weak structures. Moreover, they can be made semi-transparent for deployment on windows.

IDTech analysts predict the market for thin-film PVs will witness a Compound Annual Growth Rate (CAGR) of 10% over the next ten years, thanks to emerging technologies like perovskite PVs.


Costs vs. Efficiency and Durability

Thin-film solar cells are targeted for small self-powered electronics and the IoT (Internet of Things) sector, which is expected to grow significantly in the coming years. For these applications, high power and high efficiency are not strict requirements. Though thin-film technology has always been cheaper but less efficient than conventional silicon-based solar technology, engineers believe PV cells with 10-15% efficiency could be sufficient to operate most portable electronics.

Another feature thin films trade for costs is durability. Many gadgets are intended for short-term use as they update with newer models, relaxing the need for long-life solar cells. If the prices are lower and the cells can demonstrate viable performance, they can replace batteries in portable electronic devices.


Potential Thin-Film Technologies

Two mainstream thin-film technologies are Cadmium Telluride (CdTe) and Copper Indium Gallium Selenide (CIGS), and CdTe currently dominates the thin-film market. There have been concerns about tellurium scarcity, but the market is expected to hold due to recovery and recycling initiatives.

CIGS solar cells are made by depositing a thin layer of CIGS solution on substrates along with the electrodes. The solution has a high absorption coefficient and absorbs sunlight strongly. Therefore, the cells require thinner films of active material. Though CIGS outperforms polysilicon technology at the cell level, its module efficiency is still lower. Market analysts predict perovskite PVs will surpass the CIGS technology in the coming years.

Perovskite PV cells are easy to manufacture, do not use toxic or rare earth materials, and are suited for indoor and outdoor high power density applications. These solar cells use a perovskite-structure compound as the light-harvesting active layer. This technology has shown remarkable efficiency gains recently and has proven itself to be a scalable solution.

However, perovskite solar cells are less durable compared to conventional silicon-based technology. However, they are still suitable for low-powered electronic gadgets and some large outdoor systems.

Another less durable technology is organic photovoltaic technology, which uses organic molecules for light absorption. Their lifetime is typically five years, sufficient for short-term use of electronics. However, perovskite technology is superior to this because of simpler manufacturing.

Dye-Sensitized Solar Cells (DSSCs) are another contender in this segment for which, like organic PVs, the application range is limited to short-term use electronics due to their short lifespans. In DSSCs, a semiconductor is formed between a photo-sensitized anode that absorbs photons and an electrolyte to create a photochemical system. However, they are sensitive to high and low temperatures. At high temperatures, the electrolyte expands, making it unusable. At low temperatures, it can freeze.

Some of these thin-film technologies have already hit the market. There are wireless headphones powered by DSSCs, and Adidas has recently announced a partnership with a DSSC manufacturer. Organic solar cells are useful in small-scale sensors and counters. Furthermore, engineers and analysts believe perovskite PVs will join this burgeoning market soon.


Featured image used courtesy of Adobe Stock