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This paper seeks to elucidate the influence on the surface wettability of a variety of substituents located in different positions of the perylene bisimide (PBI) core (ortho versus imide) with distinct electron-donor or -withdrawing character and diverse steric demand, using for this more than 20 planar PBIs. The correlation between the polarity of the individual functional group on the PBI and the surface wettability has been addressed by means of substituent descriptors in terms of Hansch-Fujita π parameter, Hammett σ meta and σ para constants, and steric parameters (Taft-Dubois Es' and Charton υ). With these parameters, a quantitative structure–property relationship (QSPR) analysis has been performed using multivariable linear regression (MLR) fittings. The relationship of Surface Energy, determined by the static contact angle method with three different solvents, to structural properties of PBIs is described. As well, the polar and dispersive contributions have been determined. For planar PBIs, a predominant influence of the substituents in the imide position on the surface wettability has been found despite of the electronic nature and steric hindrance of the substituents simultaneously located in ortho positions. This effect is more pronounced with the longer alkyl substituents at the imide position. This study paves the way for a rational chromophore design considering the on surface behavior, which will ultimately condition the contact and thus their performance in optoelectronic devices. [Display omitted] • Influence on the surface wettability and surface energy of substituents located on different positions, namely imide and ortho, of the perylene bisimide (PBI) core. • Electronic and steric effects together with lipophilicity of the substituents condition the surface wettability. • Multivariable linear regression fittings based on substituents descriptors allow a rational chromophore design considering the on surface behavior. • Influence of the substituents located in the imide position of planar PBI prevails on the surface wettability. [ABSTRACT FROM AUTHOR]

We studied the effect of the charge transport layers in p-i-n perovskite solar cells using vacuum deposited methylammonium lead iodide thin-film absorbers. While solution-processed perovskite films are frequently deposited directly on PEDOT:PSS leading to good solar cell performances, in some cases even to very good V oc values, we show that in devices employing vacuum deposited MAPbI 3 perovskites, the removal of the polyTPD electron blocker substantially reduces the photovoltaic behavior. This is indicative of rather different charge transport properties in the vacuum deposited MAPbI 3 perovskites compared to those prepared from solution. On the other hand, we investigated the use of ionic interlayers as a possible alternative to low work function electrodes, whose reactivity towards air and moisture compromises the device stability. Two different electron extraction materials were evaluated as interlayers between the fullerene electron transport layer and a silver electrode, in particular a perylenediimide derivative and a conjugated polyelectrolyte. By studying the photovoltaic response and the electroluminescence properties of planar diodes using the ionic films and comparing them with devices employing barium, we found that such ionic interlayers can successfully replace the use of reactive electrodes, since they facilitate the electron extraction while reducing the non-radiative recombination at the electron transport interface. [ABSTRACT FROM AUTHOR]