In Situ Solution‐Processed Submicron Thick SiO<sub>x</sub>C<sub>y</sub>/a‐SiN<sub>x</sub>(O):H Composite Barrier Film for Polymer:Non‐Fullerene Photovoltaics
Jian Qin, Na Wu, Wei Chen, Bowen Liu, Zhenguo Wang, Lianping Zhang, Ni Yin, Qi Chen, Zong‐Bo Zhang, Chang‐Qi Ma
Abstract
Abstract Aiming to improve the environmental stability of organic photovoltaics, a multilayered SiO x C y /a‐SiN x (O):H composite barrier film coated with a hydrophobic perfluoro copolymer stop layer for polymer:non‐fullerene solar cells is developed. The composite film is prepared by spin‐coating of polysilicone and perhydropolysilazane (PHPS) following a densification process by vacuum ultraviolet irradiation in an inert atmosphere. The transformation of polysilicone and PHPS to SiO x C y and a‐SiN x (O):H is confirmed by Fourier transform infrared and energy‐dispersive X‐ray spectroscopy measurement. However, the as‐prepared PHPS‐derived silicon nitride (PDSN) can react with moisture in the ambient atmosphere, yielding microscale defects and a consequent poor barrier performance. Treating the incomplete PDSN with methanol vapor significantly densifies the film yielding low water vapor transmission rates (WVTRs)of 5.0 × 10 −1 and 2.0 × 10 −1 g m −2 d −1 for the one‐ and three‐couple of SiO x C y /a‐SiN x (O):H (CON) composite films, respectively. By incorporating a thin hydrophobic perfluoro copolymer layer, the three‐coupled methanol‐treated CON film with a total thickness of 600 nm shows an extremely low WVTR of 8.7 × 10 −4 g m −2 d −1 . No performance decay is measured for the PM6:Y6 and PM6:L8‐BO cells after such an encapsulation process. These encapsulated polymer cells show good stability storaged at 25 °C/50% relative humidity, or under simulated extreme rainstorm tests.