To develop highly efficient perovskite solar cells, applications of hybrid metal halide perovskites (such as MAPbI₃) are currently being extensively studied, but there is a strong concern about long-term stability of devices fabricated with this class of materials. CHEOPS aims to address the stability of the perovskite devices from two angles: first the stability of the different materials and layers and second the stability of the whole device through an optimized encapsulation scheme. One of the critical materials with regard to stability is the HTM (hole transport material). Spiro-OMeTAD has been shown to be temperature sensitive. Therefore CHEOPS will investigate other (organic and inorganic) HTM to overcome this problem. At the same time, encapsulation techniques are being developed and validated on module devices.
To assess the stability of perovskite solar cells it is crucial to separate the intrinsic degradation of materials and interfaces forming the perovskite modules from the degradation caused by external factors, such as environmental conditions and moisture. To this end, similarly to the case of other thin film photovoltaic technologies, it is necessary to develop an effective and rugged encapsulation method for cells and modules. Here, CHOSE (Università degli Studi di Roma 'Tor Vergata') realized an encapsulation technique applied at a perovskite module able to isolate the intrinsic degradation of perovskite solar cells from the extrinsic factors replacing the result obtained for large area perovskite devices (reported in an article published on Nano Energy journal: Encapsulation for long-term stability enhancement of perovskite solar cells).
The realization procedures used for the CHOSE encapsulation technique are the following:
- Lamination of the perovskite module using the Kapton adhesive tape deposited on the active area of the device
- Deposition of a light curable glue on the whole active area of the perovskite module
- Positioning of a protective glass
- Curing of the light-curable glue under Class A Simulator at 1Sun for 30 seconds
- Deposition of a UV-curable glue on the edge of the protective glass
- Curing of the UV glue under UV irradiation for 40s masking the active area of the perovskite module using a black adhesive