The mechanical properties of low-band-gap polymers are important for the long-term survivability of rollto-roll processed organic electronic devices. Such devices, e.g., solar cells, displays, and thin-film transistors, must survive the rigors of roll-to-roll coating and also thermal and mechanical forces in the outdoor environment and in stretchable and ultraflexible form factors. This paper measures the stiffness (tensile modulus), ductility (crack-onset strain), or both of a combinatorial library of 51 low-band-gap polymers. The purpose of this study is to systematically screen a library of low-band-gap polymers to better understand the connection between molecular structures and mechanical properties in order to design conjugated polymers that permit mechanical robustness and even extreme deformability. While one of the principal conclusions of these experiments is that the structure of an isolated molecule only partially determines the mechanical propertiesanother important codeterminant is the packing structuresome general trends can be identified. (1) Fused rings tend to increase the modulus and decrease the ductility. (2) Branched side chains have the opposite effect. Despite the rigidity of the molecular structure, the most deformable films can be surprisingly compliant (modulus ≥ 150 MPa) and ductile (crack-onset strain ≤ 68%). This paper concludes by proposing a new composite merit factor that combines the power conversion efficiency in a fully solution processed device obtained via roll and roll-to-roll coating and printing (as measured in an earlier paper) and the mechanical deformability toward the goal of producing modules that are both efficient and mechanically stable.

performance level, especially when considering large-scale mass-produced modules, is predicted to be signifi cantly lower. [ 8 ] Nevertheless, based on recent advances in the upscaling of OPV manufacture [9][10][11][12] it is reasonable to assume that the mass production of modules with an effi ciency of more than 5% is an achievable target today. Durability of OPV is however yet to be proven and demonstrated.Due to core architectural differences between OPV and inorganic technologies [ 13 ] the established testing standards of the latter are not applicable to the former. [ 1 ] Hence, for many years the stability testing of OPV has primarily been based on customized procedures that vary from one laboratory to another, generating incomparable data. [ 14 ] Moreover, due to the complexity of the OPV device architectures [ 15 ] and a multitude of aging mechanisms taking place at the same time [ 16 ] the aging curve of OPV often takes a complex shape, which is diffi cult to model, [ 14,17 ] thus making the identifi cation of a practical operational lifetime diffi cult or impossible. [ 18 ] As a result, even with a multitude of reported review articles discussing OPV stability [ 16,[19][20][21][22][23][24] at hand, it is still challenging to identify where the technology stands in terms of lifetime. To address this it is necessary to create a yardstick -a generic marker that allows accurate rating and comparison of the lifetime for OPV, and thus enabling the gauging of progress over time. An additional complication that has arisen due to the signifi cant improvements in OPV stability and durability in recent years is that the determination of OPV lifetimes has become an impractically long process, and establishing markers for both accelerated and real operational test conditions (if successful) would allow developing a prediction tool that could speed up the stability testing process and tackle this issue.The groundwork towards creating such a marker was laid in 2011 at the International Summit on OPV Stability (ISOS) where the ISOS testing guidelines were decided upon and described for OPV technologies. [ 18 ] These guidelines were primarily aimed at harmonizing testing procedures among different laboratories by offering a set of indoor and outdoor tests with controlled conditions. This has helped to reduce variations in the reported results, making the aging studies of different laboratories more comparable. [ 25 ] While the ISOS tests harmonized the test conditions, the questions of how to generically determine the lifetime from aging curves of diverse shapes, and how to build a technique for predicting the lifetime based on accelerated tests remained.The results of a meta-analysis conducted on organic photovoltaics (OPV) lifetime data reported in the literature is presented through the compilation of an extensive OPV lifetime database based on a large number of articles, followed by analysis of the large body of data. We fully reveal the progress of reported OPV lifetimes. Furthermore, a generic lifetime marker has...

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The results presented demonstrate how the screening of 104 light‐absorbing low band gap polymers for suitability in roll coated polymer solar cells can be accomplished through rational synthesis according to a matrix where 8 donor and 13 acceptor units are organized in rows and columns. Synthesis of all the polymers corresponding to all combinations of donor and acceptor units is followed by characterization of all the materials with respect to molecular weight, electrochemical energy levels, band gaps, photochemical stability, carrier mobility, and photovoltaic parameters. The photovoltaic evaluation is carried out with specific reference to scalable manufacture, which includes large area (1 cm2), stable inverted device architecture, an indium‐tin‐oxide‐free fully printed flexible front electrode with ZnO/PEDOT:PSS (poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate), and a printed silver comb back electrode structure. The matrix organization enables fast identification of active layer materials according to a weighted merit factor that includes more than simply the power conversion efficiency and is used as a method to identify the lead candidates. Based on several characteristics included in the merit factor, it is found that 13 out of the 104 synthesized polymers outperformed poly(3‐hexylthiophene) under the chosen processing conditions and thus can be suitable for further development.

The impact of additives mixed with poly(3,4‐ethylenedioxythiophene):polysty­renesulfonate (PEDOT:PSS) on the stability of organic photovoltaic modules is investigated for fully ambient roll‐to‐roll (R2R) processed indium tin oxide free modules. Four different PEDOT:PSS inks from two different suppliers are used. The modules are manufactured directly on barrier foil without a UV filter to accelerate degradation and enable completion of the study in a reasonable time span. The modules are subjected to stability testing following well‐established protocols developed by the international summit on organic photovoltaic stability (ISOS). For the harsh indoor test (ISOS‐L‐3) only a slight difference in stability is observed between the different modules. During both ISOS‐L‐3 and ISOS‐D‐3 one new failure mode is observed as a result of tiny air inclusions in the barrier foil and a R2R method is developed to detect and quantify these. During outdoor operation (ISOS‐O‐1) the use of ethylene glycol (EG) as an additive is found to drastically increase the operational stability of the modules as compared to dimethylsulfoxide (DMSO) and a new failure mode specific to modules with DMSO as the additive is identified. The data are extended in an ongoing experiment where DMSO is used as additive for long‐term outdoor testing in a solar park.