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Perovskite Solar Cells and Materials

Perovskite Solar Cell_042123A
[Perovskite Solar Cell - The City University of Hong Kong]

 

- Overview

Perovskite solar cells (PSCs) are a promising technology for renewable energy, using perovskite materials as their light-absorbing layer. These materials are known for their high efficiency, low cost, and ease of manufacturing, making them a potential alternative to traditional silicon-based solar cells.

Key aspects of PSCs and materials:

  • Perovskite Materials: These are typically hybrid organic-inorganic metal halide compounds with a specific crystal structure (ABX3), where A and B are cations and X is a halide.
  • Thin-Film Technology: PSCs are thin-film devices, meaning they are made by depositing thin layers of materials on a substrate.

 

PSCs offer several advantages over silicon, including:

  • High efficiency: Research has achieved efficiencies exceeding 25%.
  • Lower manufacturing cost: They can be produced using solution-based methods, which are less energy-intensive than traditional silicon production.
  • Flexibility: Perovskite films can be printed or coated on flexible substrates, enabling the creation of flexible solar panels.
  • Tunable absorption: The composition of perovskites can be modified to tailor their absorption of different parts of the solar spectrum, potentially leading to tandem solar cells with even higher efficiency.
 

Lightweight and flexible, these new perovskite solar panels can coat windows, walls, and even streetlights, turning urban surfaces into clean energy sources.  

In recent years, the researchers used machine learning-based algorithms and high-throughput experiments to find reliable, low-cost and identify the highest-quality perovskites from a very large field of possible structures. Research have found that it is possible to forecast the materials' dynamic behavior with very high accuracy, without the need to perform as many experiments.

Artificial intelligence (AI) is revolutionizing solar cell development by:

  • Reducing the time and cost of material discovery.
  • Optimizing solar panel designs and performance.
  • Improving energy storage and grid integration.
  • Making solar energy more affordable and accessible.

 

- Perovskite Solar Cells (PSCs)

Perovskites are a class of materials that show promise for high performance and low production costs in solar cells. 

The term "perovskite" derives from their crystal structure. These materials are also used in other energy technologies, such as fuel cells and catalysts. 

Perovskites commonly used in photovoltaic (PV) solar cells are more properly called "metal halide perovskites" because they are made of a combination of organic ions, metals, and halogens; in other applications, perovskites may be made of oxygen instead of halogens and are often entirely inorganic.

Metal halide perovskites are the main absorber material, or "active layer," in perovskite solar cells. In this potentially low-cost technology, a thin layer of perovskite absorbs light and excites charged particles called electrons; when these excited electrons are extracted, they generate electricity. PSCs are called thin-film cells because they require a much thinner active layer than crystalline silicon PV cells.

In recent years, PSCs have made significant progress, with efficiency increasing rapidly, from about 3% reported in 2009 to more than 26% on small-area devices (about 0.1 cm²) today. The efficiency of perovskite-silicon tandem cells has reached nearly 34%. 

Although PSCs have achieved high efficiency in a very short period of time, perovskite photovoltaic technology has not yet been mass-produced, and many challenges must be addressed before perovskites can become a competitive commercial photovoltaic technology.

 

 - Main Layers of Perovskite Solar Cells (PSCs)

The following is an overview of the general steps involved in producing perovskite solar cells (PSCs) and modules. Because the technology is still in the development phase, the details of each step can vary greatly between different research groups. 

This includes the elements that make up the perovskite material, the assembly of cells and modules, and the testing performed on the finished product.

A typical perovskite solar cell consists of several layers, including:

  • Transparent conductive oxide (TCO) glass substrate: Provides electrical conductivity and light transparency.
  • Blocking layer: A compact semiconductor layer (e.g., TiO2) that facilitates electron transfer.
  • Mesoporous layer: A scaffold for perovskite deposition.
  • Perovskite absorbing material: The light-harvesting layer.
  • Hole transport material (HTM): Facilitates hole transfer.
  • Back contact: Provides electrical connection.

 

- Perovskite Materials

Perovskite materials are widely considered to be the successor to silicon because they are lightweight and far cheaper to produce. However, the promise of perovskite has yet to be realized because of the difficulty of replicating lab results in mass production. 

In the field of photovoltaic technologies, silicon-based solar cells make up 90 percent of the market. In terms of cost, stability and efficiency (20-22 percent for a typical solar cell on the market), they are well ahead of the competition. However, after decades of research and investment, silicon-based solar cells are now close to their maximum theoretical efficiency. 

As a result, new concepts are required to achieve a long-term reduction in solar electricity prices and allow photovoltaic technology to become a more widely adopted way of generating power. 

One solution is to place two different types of solar cells on top of each other to maximize the conversion of light rays into electrical power. These "double-junction" cells are being widely researched in the scientific community, but are expensive to make. Perovskite's unique properties have prompted a great deal of research into its use in solar cells over the last few years. Perovskite allows high conversion efficiency to be achieved at a potentially limited production cost.

 

- Main Challenges of Perovskite Devices

A major challenge in the field is that perovskite devices are more prone to degradation than silicon when exposed to moisture, oxygen, light, heat and voltage. The problem is to find which perovskites combine high-efficiency performance with adaptability to environmental conditions.

Despite their promise, perovskite solar cells face some challenges:

  • Stability: They are susceptible to degradation from moisture, oxygen, and heat, leading to a shorter lifespan compared to silicon cells.
  • Toxic materials: Some perovskite materials contain lead, which raises environmental concerns.
  • Commercialization: While research has made significant progress, commercialization still faces hurdles related to stability, scalability, and safety.

 

Perovskites have the general structure of ABX3, where A is an organic (carbon-based) or inorganic group, B is lead or tin, and X is a halide (based on chlorine, iodine, or fluorine, or combinations thereof). 

As a result, "the number of possible chemical combinations is simply enormous.  Furthermore, they require separate and combined evaluations against multiple environmental conditions, which renders the hyperparameter space impossible to explore using traditional trial-and-error methods.

The chemical parameter space is huge. Testing all of them would be time consuming and tedious.

 

Perovskite Solar Cell_NREL_062022A
[Perovskite Solar Cell - Dennis Schroeder / National Renewable Energy Laboratory]

- Achievements, Challenges, and Future Prospects for Industrialization of Perovskite Solar Cells (PSCs)

Perovskite solar cells (PSCs) have seen remarkable progress, achieving high power conversion efficiencies (PCEs) and holding significant promise for industrialization. However, challenges remain in achieving stable, large-scale production and overcoming limitations in device stability and cost. 

Future prospects include further improvements in stability, cost reduction, and development of flexible and printable PSCs.

1. Achievements:

  • High Power Conversion Efficiencies (PCEs): PSCs have demonstrated rapid advancements in PCE, exceeding 26% in single-junction devices and reaching nearly 30% in silicon-based tandem cells.
  • Potential for low-cost production: Perovskite materials are relatively inexpensive and simple to manufacture, making them attractive for industrialization.
  • Flexibility and printability: PSCs can be deposited as thin films and have the potential for flexible and printable applications.
  • Roll-to-roll processing: Techniques like slot-die coating enable high-throughput, continuous production of PSCs.


2. Challenges:

  • Stability: PSCs are known for their instability under various conditions, including moisture, UV light, and heat, leading to degradation.
  • Cost: While potentially lower than silicon-based solar cells, further cost reduction is needed for widespread adoption.
  • Manufacturing scalability: Scaling up PSC production to industrial levels requires overcoming challenges in device uniformity and large-area deposition.
  • Material and solvent issues: Optimizing perovskite material compositions and solvents for efficient and stable device performance is crucial.


3. Future Prospects: 

  • Improved stability: Ongoing research focuses on developing passivation layers, encapsulation techniques, and alternative perovskite compositions to enhance device stability.
  • Cost reduction: Exploring cheaper perovskite materials, optimizing fabrication processes, and reducing material usage are key to lowering production costs.
  • Flexible and printable PSCs: Developing flexible and printable PSCs opens up new applications, such as wearable electronics and building-integrated solar energy systems.
  • Tandem structures: Combining PSCs with silicon or other materials to create tandem solar cells can further improve PCE and stability.
  • AI-driven materials discovery: AI can help accelerate the search for new perovskite materials with enhanced properties.

 

- AI in Finding Reliable and Low-cost Solar Cells 

Artificial intelligence (AI) and machine learning (ML) are accelerating the development of more reliable and low-cost solar cells by identifying new materials, optimizing existing designs, and automating the design process. AI can accelerate material discovery, predict material properties, and even optimize the overall solar panel system, leading to improvements in efficiency and cost-effectiveness. 

Here's how AI is contributing to reliable and low-cost solar cells:

  • Accelerated Material Discovery: ML algorithms can analyze vast amounts of data on material properties and solar cell performance to predict which materials and structures will yield the best results, according to a study on Wiley Online Library. This allows researchers to identify new materials and structures with significantly reduced experimental time and cost, as reported on Technology Networks. AI can also help identify perovskite materials, a promising alternative to silicon-based solar cells.
  • Optimized Design and Performance: AI can analyze data on solar cell performance under various conditions (weather, irradiance, etc.) to identify optimal designs and operational parameters, as described in an article on Signity Solutions. This includes optimizing panel tilt and tracking systems to maximize sunlight capture, and managing energy flow between panels, batteries, and the grid, according to Signity Solutions. AI can also improve the efficiency of energy storage and distribution, making solar energy more reliable and predictable.
  • Cost Reduction: By accelerating material discovery and optimizing designs, AI can lead to lower production costs and higher efficiency, making solar energy more accessible and affordable. AI-driven optimization of solar panel systems can also reduce energy bills for individuals and communities.

 

 

[More to come ...]



 

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