The functionality of organic semiconductor devices crucially depends on molecular energies, namely the ionisation energy and the electron affinity. Ionisation energy and electron affinity values of thin films are, however, sensitive to film morphology and composition, making their prediction challenging. In a combined experimental and simulation study on zinc-phthalocyanine and its fluorinated derivatives, we show that changes in ionisation energy as a function of molecular orientation in neat films or mixing ratio in blends are proportional to the molecular quadrupole component along the π-π-stacking direction. We apply these findings to organic solar cells and demonstrate how the electrostatic interactions can be tuned to optimise the energy of the charge-transfer state at the donor−acceptor interface and the dissociation barrier for free charge carrier generation. The confirmation of the correlation between interfacial energies and quadrupole moments for other materials indicates its relevance for small molecules and polymers.

High photon energy losses limit the open‐circuit voltage (VOC) and power conversion efficiency of organic solar cells (OSCs). In this work, an optimization route is presented which increases the VOC by reducing the interfacial area between donor (D) and acceptor (A). This optimization route concerns a cascade device architecture in which the introduction of discontinuous interlayers between alpha‐sexithiophene (α‐6T) (D) and chloroboron subnaphthalocyanine (SubNc) (A) increases the VOC of an α‐6T/SubNc/SubPc fullerene‐free cascade OSC from 0.98 V to 1.16 V. This increase of 0.18 V is attributed solely to the suppression of nonradiative recombination at the D–A interface. By accurately measuring the optical gap (Eopt) and the energy of the charge‐transfer state (ECT) of the studied OSC, a detailed analysis of the overall voltage losses is performed. Eopt – qVOC losses of 0.58 eV, which are among the lowest observed for OSCs, are obtained. Most importantly, for the VOC‐optimized devices, the low‐energy (700 nm) external quantum efficiency (EQE) peak remains high at 79%, despite a minimal driving force for charge separation of less than 10 meV. This work shows that low‐voltage losses can be combined with a high EQE in organic photovoltaic devices.

A variety of fluorinated phenols, biaryls, 6H-benzo[c]chromen-6-ones and fluorenones were prepared based on regioselective [3+3] cyclizations of 1,3-bis(silyl enol ethers) with 2-fluoro-3-silyloxy-2-en-1-ones.

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