The functional layers that a perovskite solar cell consists, could be fabricated using roll-to-roll production techniques, which offer high-throughput and cost-effective manufacturing processes. Here is a description of each layer in a perovskite stack and its potential roll-to-roll application:
1. Substrate: The substrate layer provides mechanical support for the entire device and can be a flexible material such as plastic or metal foil. Roll-to-roll production allows for continuous deposition of the substrate material on a large-scale roll, enabling the fabrication of flexible solar cells.
2. Transparent Conductive Oxide (TCO) Electrode: This layer is typically made of materials like indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) and serves as a transparent electrode to allow light to pass through while collecting the generated charges. Roll-to-roll techniques, such as sputtering or chemical vapor deposition, can be used to deposit a uniform and conductive TCO layer on the substrate.
3. Electron Transport Layer (ETL): The ETL facilitates the extraction of electrons from the perovskite layer and their efficient transport to the electrode. Materials like titanium dioxide (TiO2) or zinc oxide (ZnO) nanoparticles are commonly used. Roll-to-roll methods like slot-die coating or spray coating can be employed to deposit the ETL layer uniformly over large areas.
4. Perovskite Absorber Layer: This layer is the heart of the perovskite solar cell, consisting of an organometal halide perovskite material. The perovskite layer absorbs sunlight and generates electron-hole pairs. Various techniques, such as spin coating, inkjet printing, or blade coating, can be adapted for roll-to-roll production to deposit a continuous and uniform perovskite layer on the ETL.
5. Hole Transport Layer (HTL): The HTL assists in the selective extraction and transport of the holes (positive charges) generated in the perovskite layer. Materials like polymeric hole-transport materials or small molecules like spiro-OMeTAD are commonly used. Roll-to-roll methods such as doctor blade coating or screen printing can be utilized to deposit the HTL layer uniformly on top of the perovskite layer.
6. Metal Electrode: The metal electrode layer, often made of materials like silver or gold, collects the holes generated in the perovskite layer and completes the electrical circuit. Roll-to-roll techniques like thermal evaporation or sputtering can be employed to deposit a thin metal electrode layer on top of the HTL.
Roll-to-roll production allows for the continuous deposition of each layer on a flexible substrate, enabling the manufacturing of perovskite solar cells in a cost-effective and scalable manner. Techniques such as slot-die coating, spray coating, inkjet printing, blade coating, doctor blade coating, and screen printing are all compatible with roll-to-roll processes and can be adapted for each layer of the perovskite stack. These methods ensure uniformity, high throughput, and precise control over layer thickness, making roll-to-roll production an attractive option for large-scale manufacturing of perovskite solar cells.