Stability of Perovskite Films Encapsulated in Single- and Multi-Layer Graphene Barriers

Abstract

This paper describes the efficacy of barrier films coated with single- and multi-layer graphene in preventing degradation of perovskite films in air. Despite the impermeability of graphene to small species such as water and oxygen, the presence of numerous grain boundaries and defects in chemical vapor deposition (CVD)-grown graphene monolayer films can present pathways for permeation. However, the availability of these pathways can in principle be reduced by stacking multiple layers of graphene on top of each other. The barrier material considered here consists of the semi-permeable polymer parylene laminated with either 0, 1, 2, or 3 monolayers of graphene. These composite films are used to encapsulate triple cation perovskite films, which are then subjected to a degradation test under damp heat. We find that a monolayer of graphene confers a 15-fold reduction in degradation compared to the parylene films with no graphene and that three-layer graphene can yield a further 2× reduction in degradation. Although all of our films encapsulated with graphene/parylene exhibited substantial degradation compared to films encapsulated in glass with polyisobutylene edge seals, our results nonetheless reinforce the utility of graphene barriers for less demanding applications, including lightweight or flexible perovskite solar cells with shorter anticipated lifetimes.

Recent advances of two-dimensional material additives in hybrid perovskite solar cells

“…Another recent demonstration by Ibrahim et al showed that the direct or interfacial incorporation of highly hydrophobic, halogenated graphene particles into the spiro-OMe-TAD HTL significantly enhanced the stability of perovskite layer, demonstrating only 18% reduction in the perovskite optical absorption after 6000 h storage in ambient air with 30%-40% RH [38]. Similarly, graphene synthesized by CVD was also shown to be effective in improving the stability of PSC: Hu et al reported the insertion of a CVD graphene between the Au electrode and spiro-OMeTAD in planar PSCs to block the diffusion of air and Au into the perovskite layer [39], demonstrating the retention of >95% of the initial PCE under 96 h storage in ambient air with 45% RH, as well as 96% of the PCE under 80 °C in an inert atmosphere for 12 h. This is consistent to a prior report by Runser et al in which mono-and multi-layer CVD graphene could prevent the degradation of the perovskite film itself in air by acting as an effective encapsulation layer [40].…”

Comparison of Glass–Glass versus Glass–Backsheet Encapsulation Applied to Carbon-Based Perovskite Solar Cells

“…This finally leads to the quite equivalent durability of both studied systems, even if, in terms of WVTR, the PIB edge-sealant is more efficient than the used ionomer, and glass is more protective than the barrier polymer used as backsheet. According to the literature, other materials are currently being studied in order to increase the barrier properties of traditional encapsulating materials (for instance, multi-walled carbon nanotubes as an additive in epoxy resin [49] or graphene layers colaminated with polymers [50]). A non-negligible advantage in our study is that TiO 2 and carbon are quite cheap materials that also participate in the photovoltaic conversion themselves while delaying the moisture ingress.…”

Encapsulation and Stability Testing of Perovskite Solar Cells for Real Life Applications

“…A variety of encapsulation materials and techniques have been reported in the literature, such as EVA, ,,, PVB, , PIB, ,,,− ,, fluoropolymeric coating, , TPU, , ethylene methyl acrylate, cyclized perfluoro-polymer (Cytop), organic–inorganic hybrid materials ORMOCERs, ORMOSIL aero-gel thin film, various polymer films, PDMS, PET, polytetrafluoroethylene (PTFE), polycarbonate (PC), polyimide (Kapton) tape, Surlyn, , POE ENLIGHT, oxide thin films deposited by various methods, − graphene/parylene with PIB edge seal, various UV curable epoxies (Threebond, Vitralit epoxy glue by Panacol, Ossila E132 resin, Ossila Encapsulation Epoxy E131, Norland optical adhesive, Nagase Chemtex), ,− etc.…”