We analyze the voltage losses at open circuit in solutionprocessed, small-molecule:fullerene blend solar cells, using electroluminescence and external quantum efficiency measurements and the reciprocity relationship between light absorption and emission. For solar cells made from oligothienylenevinylene-based donors and phenyl-C 71 butyric acid methyl ester (PC 71 BM), we find that the voltage loss due to the finite breadth of the absorption edge is remarkably small, less than 0.01 eV in the best cases, while the voltage loss due to nonradiative recombination reaches 0.29 eV, one of the smallest values reported for an organic solar cell. As a result, the open-circuit voltage reaches around 1.0 V for an optical gap of 1.6 eV, greatly exceeding the voltage of a high-performance polymer-based system with similar optical gap. We assign the remarkably small absorption broadening loss to a low degree of energetic disorder in the small-molecule system that allows efficient charge separation at a lower driving force than in typical conjugated polymer blends.

A series of three small‐molecule acceptor–donor–acceptor (A‐D‐A) compounds with a tetraaryl‐1,4‐dihydropyrrolo[3,2‐b]pyrrole as the central building block were synthesized and fully characterized. These molecules present high thermal stability and suitable HOMO–LUMO energy levels making them feasible electron‐donor materials in bulk heterojunction organic solar cells (BHJ‐OSC). Moreover, theoretical work predicts of a lack of planarity and no π–π stacking, furthermore. The electron density of the HOMO is distributed on the pyrrole–pyrrole moiety and that of the LUMO is delocalized, in contrast, on the phenyl groups. The organic solar cells deliver an open‐circuit voltage of 0.99 V. However, the overall efficiency is limited due to the low charge mobility measured for holes, 10−9 cm2 V−1 s−1.

This work is focused on unraveling the mechanisms responsible for the aggregation‐induced enhanced emission and solid‐state luminescence enhancement effects observed in star‐shaped molecules based on 1,3,5‐tris(styryl)benzene and tri(styryl)‐s‐triazine cores. To achieve this, the photophysical properties of this set of molecules were analyzed in three states: free molecules, molecular aggregates in solution, and the solid state. Different spectroscopy and microscopy experiments and DFT calculations were conducted to scrutinize the causative mechanisms of the luminescence enhancement phenomenon observed in some experimental conditions. Enhanced luminescence emission was interpreted in the context of short‐ and long‐range excitonic coupling mechanisms and the restriction of intramolecular vibrations. Additionally, we found that the formation of π‐stacking aggregates could block E/Z photoisomerization through torsional motions between phenylene rings in the excited state, and hence, enhancing the luminescence of the system.

A set of five novel oligo-thienylenevinylene organic molecules have been synthesized and characterized for use as electron donor moieties in bulk-heterojunction solution-processed organic solar cells combined with PC71BM as an electron acceptor.