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New Electron Transport Materials for High Performance Organic Solar Cells: Synthesis and Properties of Symmetrical and Asymmetrical 1,4,5,8‐Naphthalenetetracarboxylic Dianhydride Derivatives

Two series – symmetrical and asymmetrical – of electron‐transporting 1,4,5,8‐naphthalenetetracarboxylic dianhydride derivatives are designed and synthesized. The compounds show high thermal stability with initial destruction temperatures reaching 481 °C. The materials absorb light in UV–visible region, however, avoiding parasitic absorption that makes them suitable for the usage in high performance solar cells. Cyclic voltammetry deduces relatively high electron affinity (3.84–4.10 eV) indicating strong electron accepting nature of the molecules. The synthesized compounds have remarkable electrical properties such as high conductivity (up to 4 × 10−5 S cm−1) and electron mobility (up to 10−3 cm2 V−1 s−1). The highest solar cell efficiency is obtained for asymmetrical adduct of 1,4,5,8‐naphthalenetetracarboxylic dianhydride, pyridine‐3‐amine, and pyridin‐3,4‐diamine, and exceeds the efficiency of the reference material C60. A comparative study of the experimentally estimated and theoretically calculated by means of density functional theory method characteristics of the electron‐transporting materials is presented. The control of the symmetry of the molecular structures is responsible for the high performance of compounds in the target devices.