In this blog post, we explore whether dye-sensitized solar cells can efficiently harness solar energy to become a sustainable energy source.
On sunny days, beneath clear skies, we often feel the warmth of the sun. But this warmth isn’t merely pleasant heat; scientifically analyzed, it represents an immense energy source. The energy the sun radiates onto Earth’s surface daily is immense, and developing technology to harness it efficiently is one of modern science’s critical challenges. Sunlight provides approximately 1 kilowatt of energy per square meter. Finding ways to effectively utilize this abundant solar energy is a vital challenge for humanity. Solar cells are devices developed to convert this abundant and nearly perpetual solar energy into electrical energy.
Silicon solar cells, currently the most widely used type, are primarily employed in satellites and high-cost devices because processing their main material, silicon, is extremely expensive. This is due to the high purity and precise processing required for silicon. Consequently, new solar cell technologies are being researched as cost-effective alternatives. This research encompasses various approaches aimed not only at reducing cell costs but also at maximizing energy conversion efficiency. Consequently, solar cells utilizing easily obtainable and low-cost titanium oxide as a photocatalyst have been developed. However, titanium oxide has the drawback that it can only utilize light wavelengths below approximately 400 nanometers, specifically the ultraviolet spectrum, for power generation. This ultraviolet light constitutes only about 4-5% of the sunlight reaching Earth’s surface, a very small amount. To overcome this limitation, the ‘dye-sensitized solar cell’ was developed by applying the principles of artificial photosynthesis.
Artificial photosynthesis is a technology that mimics the complex and sophisticated energy conversion process occurring in nature, applying the method by which plants utilize sunlight to produce energy. Plants utilize nearly 100% of sunlight’s energy to create and use the energy they need. Artificial photosynthesis is the technology developed to mimic this sophisticated plant system and enhance energy conversion efficiency. While plants use water and carbon dioxide to produce organic matter and oxygen in this process, artificial photosynthesis technology primarily focuses on converting solar energy into electrical energy or decomposing water to produce hydrogen. These technologies are expected to play a crucial role not only in electricity generation but also in producing hydrogen, a key clean energy resource for the future.
In the process where plants absorb sunlight to create energy sources, pigments like chlorophyll play a vital role in capturing solar energy. Pigment-enhanced solar cells mimic this principle of photosynthesis. They adsorb photosensitive dyes (pigments) onto titanium oxide thin films. These dyes allow electrons to be easily excited even in the visible light range (wavelengths of 500 to 600 nanometers), enabling more sunlight to be utilized for power generation. Electrons excited by light in the dye are injected into the conduction band of the titanium oxide. As these electrons move from the cathode to the anode, a current flows. The dye, having released its electrons, returns to an electrically neutral state through the redox reaction of iodine (I) contained in the electrolyte, thereby generating electricity. This cell uses fine titanium oxide particles, 10 to 30 nanometers in diameter, as electrodes. Microfabrication maximizes the surface area of the titanium oxide, allowing it to adsorb as much dye as possible.
Research has shown that dye-sensitized solar cells convert over 50% of the light energy collected by the dye molecules into electrical energy, demonstrating significantly higher energy conversion efficiency than previous solar cells. Moreover, hydrogen, which is gaining attention as a clean energy source, can be produced much more economically. By using photocatalysts to decompose water and obtain oxygen and hydrogen, it is far more efficient than the previous method of using electricity generated from sunlight to decompose water and obtain hydrogen. The advancement of this technology is expected to bring significant changes to future energy production methods and make an important contribution to the development of sustainable energy resources. Moreover, not only is it easy to create as a transparent thin film that allows light to pass through, but recently, cells using PET film as a substrate have also been developed, raising expectations for even more diverse applications. This opens the possibility for solar cells to be more easily integrated into future buildings and electronic devices.
