Polymer grain encapsulation in perovskite solar cells (PSCs) offers multiple significant benefits that enhance device performance, stability, and durability. These benefits stem from the unique properties polymers impart at the grain boundaries and within the perovskite film itself:
Benefits of Polymer Grain Encapsulation for Perovskite Solar Cells
1. Enhanced Moisture Resistance and Stability
- The polymer encapsulation forms a hydrophobic barrier around perovskite grains, substantially improving moisture resistance. For example, devices encapsulated with certain stepwise melting-polymerizing molecules (SMPM) demonstrate strong hydrophobicity, resisting liquid water contact for over 30 seconds and maintaining more than 95% of initial efficiency after 2000 hours in high humidity (≈85% RH) environments.
- Similarly, in situ microencapsulation of grain boundaries using polymeric epoxy reactions serves as a water molecule shield, leading to a 95-fold improvement in phase stability under 94% relative humidity and preserving 80% efficiency for over 165 hours at 70% RH.
2. Defect Passivation and Reduced Carrier Recombination
- Polymers at grain boundaries chemically interact with the perovskite, passivating defects that would otherwise serve as recombination centers for charge carriers. This reduces nonradiative recombination losses and voltage deficits, enhancing device efficiency.
- The polymer encapsulation suppresses ion migration, which also contributes to reducing defect-related degradation and recombination rates.
3. Improved Film Crystallinity and Grain Size
- Polymers can regulate the crystallization kinetics of perovskite films, slowing crystallization to yield larger grains with better crystallinity and orientation. Larger grains mean fewer grain boundaries that act as traps, leading to improved charge transport and device efficiency.
4. Mechanical Flexibility and Durability
- The elastic properties of polymers impart mechanical robustness to the perovskite layer, serving as strain regulators during bending or flexing. This is critical for flexible PSC applications, enhancing operational stability without compromising power conversion efficiency (PCE).
5. Environmental and Thermal Stability
- Polymers provide chemical inertness and gas impermeability, protecting PSCs from oxygen, moisture, and environmental contaminants. Their cross-linked networks suppress phase separation and enhance photo- and thermal stability, thus prolonging device lifespan.
6. Lead Immobilization and Environmental Safety
- The strong chelation and cross-linking properties of polymers help immobilize toxic lead ions within the perovskite layer, mitigating lead leakage concerns and improving environmental safety of PSCs.
Summary Table of Polymer Grain Encapsulation Benefits
| Benefit | Effect on Perovskite Solar Cells | Examples / Notes |
|---|---|---|
| Moisture Resistance | Hydrophobic barrier prevents water ingress | >95% efficiency retention after 2000h at ~85% RH |
| Defect Passivation | Reduces carrier recombination and voltage loss | Polymer microencapsulation acts as defect passivator |
| Improved Crystallinity | Larger, better-oriented grains improve charge transport | Polymers slow crystallization, enhance grain size |
| Mechanical Flexibility | Enhances bending durability for flexible PSCs | Elastic polymer layers suppress strain effects |
| Environmental Stability | Chemical inertness and gas impermeability enhance shelf life | Cross-linked polymers suppress phase degradation |
| Lead Immobilization | Chelation reduces lead leakage, addressing environmental concerns | Enhances PSC safety and sustainability |
In essence, polymer grain encapsulation acts as a multifunctional strategy to simultaneously boost the efficiency, moisture and environmental stability, mechanical robustness, and safety of perovskite solar cells. This approach is instrumental in advancing PSC technology toward commercialization and long-term use in diverse conditions.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-are-the-benefits-of-using-polymer-grain-encapsulation-for-perovskite-solar-cells/
