Organic solar cells are solar cells whose core components are composed of organic materials. They mainly use organic materials with photosensitive properties as semiconductor materials, and generate voltage to form current through the photovoltaic effect, thereby achieving the effect of solar power generation.
Organic solar cells, as a novel type of solar cell device, possess characteristics such as flexibility, light weight, tunable color, solution processing, and large-area printing fabrication, making them a current hot topic in solar cell research. However, low efficiency is the main reason limiting their large-scale application.
I. The Principle of Organic Solar Cells
Organic solar cells use photosensitive organic materials as semiconductors, generating voltage and forming current through the photovoltaic effect. The main photosensitive organic materials all possess conjugated structures and are conductive, such as phthalocyanine compounds, porphyrins, and cyanines.
II. Structure of Organic Solar Cells
Organic solar cells can be classified according to the semiconductor materials into single-junction structure, PN heterojunction structure, and dye-sensitized nanocrystalline structure.
1. Simple knot structure
The single-junction structure is an organic solar cell fabricated based on the Schotty barrier principle. Its structure consists of a glass/metal electrode/dye/metal electrode, utilizing the difference in work function between the two electrodes to generate an electric field. Electrons are transferred from the metal electrode with a low work function to the electrode with a high work function, thus producing a photocurrent. Because electrons and holes are transported within the same material, its photoelectric conversion efficiency is relatively low.
2. P—N
A heterojunction structure (PN junction) refers to a heterojunction structure with donor-acceptor (N-type semiconductor and P-type semiconductor), as shown in Figure 5. The semiconductor material is often a dye, such as phthalocyanine compounds or perylene tetramethylaldehyde imine compounds. The separation efficiency is improved by utilizing the D/A interface (donor, acceptor) between the semiconductor layers and the characteristic that electrons and holes are transferred between different materials. Elias Stathatos et al. combined the advantages of inorganic and organic compounds to create solar cells with a photoelectric conversion efficiency of 5%–6%.
3. NPC (nanocrystaline photovoltaic cell) dye-sensitized nanocrystals
Dye-sensitized solar cells (DSSCs) mainly refer to a type of solar cell that uses dye-sensitized porous nanostructured TiO2 thin films as photoanodes. They are solar cells that mimic the photosynthetic principle of plant chlorophyll. In contrast, NPC solar cells can utilize appropriate redox electrolytes to improve photoelectric efficiency, typically stabilizing at around 10%. Furthermore, nanocrystalline TiO2 is easy to prepare, inexpensive, and has a considerable lifespan, making it a promising market prospect.
