Search

Donor-acceptor systems, group 14 elements, organic photovoltaics, organometallics, perylene diimides Keywords: donor-acceptor systems; group 14 elements; organic photovoltaics; organometallics; perylene diimides EN donor-acceptor systems group 14 elements organic photovoltaics organometallics perylene diimides 1 1 1 10/18/23 20231013 NES 231013 B Profiting from inorganic modifications b : The organic perylene structure was functionalized with inorganic silicon and germanium atoms. Cover Feature: Silicon- and Germanium-Functionalized Perylene Diimides: Synthesis, Optoelectronic Properties, and Their Application as Non-fullerene Acceptors in Organic Solar Cells (Chem. Eur. J. 57/2023). [Extracted from the article]

Organic solar cells have been continuously studied and developed through the last decades. A major step in their development was the introduction of fused-ring non-fullerene electron acceptors. Yet, beside their high efficiency, they suffer from complex synthesis and stability issues. Perylene-based non-fullerene acceptors, in contrast, can be prepared in only a few steps and display good photochemical and thermal stability. Herein, we introduce four monomeric perylene diimide acceptors obtained in a three-step synthesis. In these molecules, the semimetals silicon and germanium were added in the bay position, on one or both sides of the molecules, resulting in asymmetric and symmetric compounds with a red-shifted absorption compared to unsubstituted perylene diimide. Introducing two germanium atoms improved the crystallinity and charge carrier mobility in the blend with the conjugated polymer PM6. In addition, charge carrier separation is significantly influenced by the high crystallinity of this blend, as shown by transient absorption spectroscopy. As a result, the solar cells reached a power conversion efficiency of 5.38 %, which is one of the highest efficiencies of monomeric perylene diimide-based solar cells recorded to date., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Cu 3 BiS 3 thin films are fabricated via spin coating of precursor solutions containing copper and bismuth xanthates onto planar glass substrates or mesoporous metal oxide scaffolds followed by annealing at 300 °C to convert the metal xanthates into copper bismuth sulfide. Detailed insights into the film formation are gained from time-resolved simultaneous small and wide angle X-ray scattering measurements. The Cu 3 BiS 3 films show a high absorption coefficient and a band gap of 1.55 eV, which makes them attractive for application in photovoltaic devices. Transient absorption spectroscopic measurements reveal that charge generation yields in mesoporous TiO 2 /Cu 3 BiS 3 heterojunctions can be significantly improved by the introduction of an In 2 S 3 interlayer, and long-lived charge carriers ( t 50% of 10 μs) are found.

Methylammonium lead iodide (MAPI) cells of the design FTO/sTiO2/mpTiO2/MAPI/Spiro-OMeTAD/Au, where FTO is fluorine-doped tin oxide, sTiO2 indicates solid-TiO2, and mpTiO2 is mesoporous TiO2, are studied using transient photovoltage (TPV), differential capacitance, charge extraction, current interrupt, and chronophotoamperometry. We show that in mpTiO2/MAPI cells there are two kinds of extractable charge stored under operation: a capacitive electronic charge (∼0.2 μC/cm(2)) and another, larger charge (40 μC/cm(2)), possibly related to mobile ions. Transient photovoltage decays are strongly double exponential with two time constants that differ by a factor of ∼5, independent of bias light intensity. The fast decay (∼1 μs at 1 sun) is assigned to the predominant charge recombination pathway in the cell. We examine and reject the possibility that the fast decay is due to ferroelectric relaxation or to the bulk photovoltaic effect. Like many MAPI solar cells, the studied cells show significant J-V hysteresis. Capacitance vs open circuit voltage (V(oc)) data indicate that the hysteresis involves a change in internal potential gradients, likely a shift in band offset at the TiO2/MAPI interface. The TPV results show that the V(oc) hysteresis is not due to a change in recombination rate constant. Calculation of recombination flux at V(oc) suggests that the hysteresis is also not due to an increase in charge separation efficiency and that charge generation is not a function of applied bias. We also show that the J-V hysteresis is not a light driven effect but is caused by exposure to electrical bias, light or dark.