Abstract
Long-term stability of perovskite solar cells (PSCs) is one of the main issues to be solved for forthcoming commercialization of this technology. In this work, thermosetting polyurethane (PU)-based resins are proposed as effective encapsulants for perovskite solar cells to prevent degradation caused by both moisture and oxygen. Application consists of drop-casting the precursor mixture directly over the devices followed by in situ polymerization, avoiding the use of other adhesives. PUs are cost-effective, lightweight, thermal, and light-stable materials whose mechanical, chemical, and physical properties can be easily tuned by thoughtful choice of their precursor. Encapsulated PSCs show extremely good stability when stored under ambient light (maximum, 1000 lux), controlled humidity (28–65%), and temperature (18–30 °C) by retaining 94% of the initial power conversion efficiency after 2500 h (4 months), whereas control devices lose 90% of their performance after 500 h (T80 = 37 h); once stored according to ISOS-D-1, PU-protected devices showed T80 > 1200 h. Encapsulated devices are stable even when immersed in pure water. The demonstration of PUs as promising solution-processed encapsulant materials for PSCs can pave the way for these to become a cost-effective encapsulation route alternative for future industrialization of this technology.
Highlights
In the past years, perovskite solar cells (PSCs) attracted huge attention from scientists involved in the photovoltaic field due to their impressive solar-to-electrical energy conversion efficiency.[1]
PSCs remarkably outperformed other recent technologies, such as dye-sensitized solar cells (DSSCs)[2] and organic photovoltaics (OPVs),[3] and they have recently approached the efficiency of classical PVs, e.g., Si-based devices
Aiming at choosing the most suitable polyurethane-based thermosetting polymer, we screened six different bicomponent resins, obtained combining three different diisocyanate precursor (IC) mixtures mainly based on two aliphatic molecules (i.e., hexamethylenediisocyanate (HDI) and isophorone diisocyanate (IPDI)) and two polyol (PO) formulations (Figure 1)
Summary
Perovskite solar cells (PSCs) attracted huge attention from scientists involved in the photovoltaic field due to their impressive solar-to-electrical energy conversion efficiency.[1]. Most of the adhesives are not chemically inert toward the perovskite film.[17] when applied in PSCs, glass-based encapsulation almost doubles the overall weight of the device, leading to halving of the photoconversion efficiency/weight ratio.[25] This could heavily jeopardize the feasible and cost-effective implementation at the industry scale In this context, a great amount of effort has been recently made to realize glass-free encapsulation.[26] For example, Dameron et al.[27] reported on the use of a multilayer of various metal oxides (i.e., Al2O3 and SiO2) deposited by atomic layer deposition (ALD), one on the top of the other. One should notice that the results reported throughout the present paper, albeit at the initial stage, allow one to classify thermosetting PUs as “worth-toinvestigate” materials, contrary to what is usually stated by the perovskite community
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