The researchers at Switzerland’s École Polytechnique fédérale de Lausanne (EPFL) claimed to have developed dye-sensitized solar cells (DSCs) with a power conversion efficiency of 15.2% in direct sunlight and up to 30.2% in ambient light conditions.

The history of dye-sensitized solar cells began in the 1990s when Brian O’Regan and Michael Grätzel invented them. Since then, they have been popularly known as “Grätzel cells.”

“Our findings pave the way for facile access to high-performance DSCs and offer promising prospects for applications as power supply and battery replacement for low-power electronic devices that use ambient light as their energy source,” the researchers said.

Dye-sensitized solar cells convert light into electricity through photosensitizers. These dye compounds absorb light and inject electrons into an array of oxide nanocrystals, which are then collected as electric current.

The photosensitizers are attached to the surface of nanocrystalline mesoporous titanium dioxide films, which are saturated with redox-active electrolytes or solid charge-transport material. The design aims to generate electric current by moving electrons from the photosensitizer to an electrical output such as a device or storage unit.

Improvements made to increase efficiency 

Recent advancements have improved the performance of DSCs under both sunlight and ambient light conditions. The group of researchers explained that the key to enhancing the efficiency of these cells lies in understanding and controlling the arrangement of dye molecules on the surface of titanium dioxide nanoparticle films that favor the generation of electrical charge.

One method is cosensitization, a chemical manufacturing approach that produces DSCs with two or more dyes with complementary optical absorption. The method combines dyes that can absorb light from across the entire spectrum.

Alternatively, the team identified a way of improving the packing of two newly designed photosensitizer dye molecules to enhance the DSC’s photovoltaic performance by developing a technique in which a monolayer of a hydroxamic acid derivative is pre-adsorbed onto the surface of nanocrystalline mesoporous titanium dioxide. This slows the adsorption of the two sensitizers and enables the formation of a well-ordered and densely packed sensitizer layer on the titanium dioxide surface.

The dye-sensitized solar cells are transparent and can easily be manufactured in assorted colors. Typical applications include skylights, greenhouses, or glass facades. They are also suitable for portable electronic devices because they are lightweight and flexible.

Installation featuring dye-sensitized solar cells at the Swiss Tech convention center | Source: EPFL

In October, researchers from China, Australia, and Singapore recently used a tube-type industrial plasma-assisted atomic layer deposition (PEALD) method and announced a maximum power conversion efficiency of 22.8% in a 613-Watt tunnel oxide passivated contact (Topcon) module with 60 cells.

EPFL researchers in July, along with CSEM’s Sustainable Energy Centre, claimed to have set two world records by achieving an efficiency of over 30% for perovskite-on-silicon-tandem solar cells. This path-breaking milestone was independently certified by National Renewable Energy Laboratory (NREL).