When 李晏成 introduced encapsulation, he first asked the audience to picture a sealed jar at home: once the lid closes, a ring of material around it keeps water vapor and oxygen out. A perovskite solar cell needs a similar ring of protection. On a device that generates electricity, how the adhesive is applied, how it cures and where it remains all affect the result.
Conventional film lamination or thermoplastic encapsulation requires heat. Temperature and time can reduce the performance of the active layer and lengthen the production cycle. Glass, films and adhesives also expand differently with heat; after aging, gaps may form at their interfaces and give moisture a path inside.
The Eversolar AB series introduced by Everlight Chemical at the forum takes a liquid, UV-curing route. The liquid first flows into interfaces and gaps, then cures under 365 or 405 nm light. Adhesive thickness, optical power, exposure time and the temperature rise a device can tolerate together determine how quickly the step can run.
The formulation changes with its position in the device. The light-entry area needs transparency; an edge seal or non-illuminated region can prioritize barrier performance. In Everlight's public material, AB-302 is a transparent, lower-viscosity liquid formulation suitable for dispensing or slot-die coating. AB-341 is an opaque paste suitable for dispensing or screen printing. They serve different locations, so a single barrier number cannot replace the choice of application method.
At this point, 李晏成 described a customer developing a smart window. When darkened, the window was meant to remain uniformly black. If the encapsulated edge let white show through, the result resembled an early mobile phone whose display and bezel appeared in different colors. The customer asked for a black edge adhesive. Darkening the material also changed how it absorbed the curing light, so optical power and exposure time had to be recalculated. The appearance of the border became a curing condition.
Electrodes, leads and opaque regions can also block UV and leave unexposed areas. 李晏成 described the solution as dual curing: UV first cures the main illuminated area, then a second curing reaction in the formulation takes over in shadowed regions. Some customers add another seal around the outside. The adhesive must follow the shaded locations and application path; the encapsulation pattern cannot be designed independently of the device.
Later, 李晏成 showed tests for water vapor, oxygen and yellowing. Water-vapor and oxygen transmission rates can guide formulation changes, but they still measure the material itself. A complete device also contains glass–adhesive interfaces, edge seals, leads and microcracks. Whether those locations remain intact after aging appears only in device-level testing.
A 2025 Nature study provides a traceable example of AB-341 in use. The paper investigated multijunction devices rather than comparing encapsulants; AB-341 was the encapsulation material the researchers used. They encapsulated a triple-junction device—three subcells absorbing different parts of the spectrum—with a cover glass and AB-341, then cured it for three minutes under a 365 nm UV LED inside a nitrogen glovebox.
At about 25°C in ambient air, the device was continuously held at the operating point that produced maximum power. The time required for efficiency to fall to 80% of its initial value (T80) was 860 hours. Under continuous illumination equivalent to one sun at 85°C, with the device held at open circuit and delivering no external current, T80 fell to five hours.
The two tests changed temperature, illumination and operating state at the same time. The difference between 860 hours and five hours cannot be assigned to any one stressor, much less to the adhesive alone. The result belongs to the encapsulation, absorber, contacts and the entire multijunction stack under stress. Once an encapsulation scheme leaves a material specification sheet, it still has to return to the full device for testing.
After water vapor, oxygen and accelerated aging in the laboratory, 李晏成 extended the next work outdoors and also mentioned ionizing radiation in low-Earth orbit. Those tests were still being planned. The talk ended as the list of environments continued to grow, without converting the AB series into a universal product lifetime.
Sources and further reading
Talk and organizer material
- TPRIA: Light-cured encapsulation protects long-term perovskite stability and manufacturing pace: The organizer's session recap of room-temperature UV curing, secondary curing in shadowed regions, water and oxygen barriers, aging and special-environment tests. The sealed-jar analogy, smart-window color and additional outer seal come from the forum recording.
Company technical material
- Everlight Chemical: Eversolar AB series technical presentation (2025): Formulation types, application methods, 365/405 nm curing, yellowing and company durability tests.
Primary paper and testing context
- Steering perovskite precursor solutions for multijunction photovoltaics, Nature (2025): The specific AB-341 encapsulation method and device stability under two stress conditions.
- ISOS consensus statement for stability testing of perovskite photovoltaics, Nature Energy (2020): A framework for reading lifetime figures together with temperature, humidity, illumination, bias, samples and initial values.