Why OLED or OPV Need to Be Encapsulated?
Encapsulation plays a crucial role in enhancing the durability and operational life of OLED (Organic Light Emitting Diode) and OPV (Organic Photovoltaics) devices. Due to the sensitive nature of organic materials used in these devices, they are vulnerable to environmental factors like moisture, oxygen, and UV exposure. These elements can cause rapid degradation, resulting in reduced brightness, loss of efficiency, or even device failure. For instance, moisture infiltration can oxidize the cathode or disrupt the integrity of the light-emitting layer in OLEDs, while in OPVs, it can severely affect charge transport by degrading the active layer materials. Consequently, encapsulation is essential to create a barrier against these detrimental factors, ensuring reliable performance over extended periods.
Encapsulation Process
The encapsulation of OLEDs and OPVs can be achieved through various methods, each tailored to protect the device based on its intended application and environment. Among the most effective methods is thin-film encapsulation (TFE), which involves depositing alternating layers of inorganic and organic materials. This approach not only shields the device from moisture but also maintains flexibility—essential for foldable and wearable applications. Film-forming techniques like atomic layer deposition (ALD) and chemical vapor deposition (CVD) allow for highly precise thin-film barriers with low water vapor transmission rates (WVTR), meeting the rigorous protection demands for modern displays and solar cells.
Generally, laboratories do not have the aforementioned expensive film-forming equipment, and the glass- substrate devices they produce can be encapsulated using cover glass, desiccant and UV glue. For example, Lumtec’s etched glass cover (LT-Cover) effectively prevents oxygen and moisture from penetrating while maintaining optical clarity. In addition, the use of sealants such as low-permeability UV glue (LT-U001) along the edge of the cover can effectively strengthen the structure and reduce moisture penetrating into the device. A desiccant (LLDY1000001) can be placed in the cavity of the cover to absorb trace amounts of diffused moisture, further improving the packaging effect and fully maintaining the performance and life of the device.
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Encapsulation Advantages
Encapsulation offers several benefits that are pivotal for the performance of OLED and OPV devices：
- Extended Device Lifetime：Encapsulation helps maintain device performance over time by shielding sensitive layers from degrading elements. Desiccants, such as Lumtec’s Label Desiccant (LLDY1000001) or Liquid Desiccant (LLDY2000001), are effective at capturing residual moisture within the encapsulated area, thus preserving the organic materials inside and contributing to long-term operational stability.
- Enhanced Flexibility：In foldable OLED applications, encapsulation layers need to be both protective and flexible. Thin-film encapsulation, combined with desiccant solutions, ensures the OLED maintains structural integrity even when bent or folded.
- Protection Against Mechanical Stress：Encapsulation provides added mechanical resilience, protecting OLED and OPV devices from physical damage due to impacts or bending. A reliable cover glass layer, such as LT-Cover, adds durability, making it suitable for wearable and outdoor applications, where devices are often subject to rough handling.
The Future Outlook
As technology progresses, encapsulation methods for OLEDs and OPVs are expected to advance further, addressing current limitations in device lifespan, efficiency, and flexibility. The development of ultra-barrier materials with even lower water vapor transmission rates (WVTR) will be crucial, as it enables longer-lasting protection even in harsh environmental conditions. Future encapsulation strategies will likely focus on hybrid approaches that combine the mechanical strength of glass encapsulation with the flexibility of thin-film technologies. Innovations in desiccant materials, such as improved formulations for liquid and label desiccants, can also play a key role by enhancing moisture absorption without adding bulk to the device.
In addition, new encapsulation materials like self-healing polymers could potentially extend device life by autonomously repairing minor structural damages caused by bending or impacts. For commercial applications, there is a growing demand for low-cost, scalable encapsulation solutions to support the expanding market for flexible and wearable electronics. With continued research and development, encapsulation technologies are likely to enable the widespread adoption of advanced OLED and OPV devices, supporting innovations in foldable displays, high-performance solar cells, and new lighting applications that are both sustainable and efficient.
Additional Reading
Lu, Q., Yang, Z., Meng, X., Yue, Y., Ahmad, M. A., Zhang, W., Zhang, S., Zhang, Y., Liu, Z., & Chen, W. (2021). A review on encapsulation technology from organic light emitting diodes to organic and perovskite solar cells. Advanced Functional Materials, 31(41), 2100151.
