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Thin Film Encapsulation of Organic Solar Cells by Direct Deposition of Polysilazanes from Solution
Author(s) -
Channa Iftikhar Ahmed,
Distler Andreas,
Zaiser Michael,
Brabec Christoph J.,
Egelhaaf HansJoachim
Publication year - 2019
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201900598
Subject(s) - materials science , diffusion barrier , water vapor , coating , organic solar cell , encapsulation (networking) , thin film , chemical engineering , polymer , nanotechnology , optoelectronics , composite material , layer (electronics) , chemistry , organic chemistry , computer network , computer science , engineering
Organic electronic devices (OEDs), e.g., organic solar cells, degrade quickly in the presence of ambient gases, such as water vapor and oxygen. Thus, in order to extend the lifetime of flexible OEDs, they have to be protected by encapsulation. A solution‐based encapsulation method is developed, which allows the direct deposition of the diffusion barrier on top of OEDs, thus avoiding lamination of barrier films. The method is based on the deposition of a perhydropolysilazane (PHPS) ink and its subsequent conversion into a silica layer by deep UV irradiation. The resulting barrier films show water vapor transmission rates (WVTRs) of <10 −2 g m −2 d −1 (40 °C/85% relative humidity (RH)) and oxygen transmission rates (OTRs) of <10 −2 cm 3 m −2 d −1 bar −1 at ambient conditions. Flexibility of the resulting barrier films is improved by coating a barrier stack of several thin PHPS layers alternating with organic polymer interlayers. These stacks show an increase of WVTR values by less than 10% after 3000 bending cycles. Direct coating of the PHPS films on top of organic solar cells enhances the device lifetime in damp heat conditions from a few hours to beyond 300 h.