Effect of Aromatic Solvents Residuals on Electron Mobility of Organic Single Crystals

Balanced electron and hole transport properties are essential for various organic electrical/optoelectrical applications such as organic solar cells, complementary circuits, and light‐emitting transistors. However, the electron transport in organic semiconductor lags far behind the hole side, making it with vital significance to seek the factors that limit the electron mobility. Here, the authors demonstrate that the π‐conjugated solvents, as essential components in the widely‐used solution processing techniques, can significantly suppress the electron transport if they are not properly removed and trapped as residuals. Single crystals of typical p‐type materials exhibit a transition from p‐type behavior to ambipolar conductance via reducing the amount of solvent residuals, and the same effect is confirmed by varied p‐type materials and solvents. The highest electron mobility reaches 0.027 cm2 V−1 s−1 and 0.029 cm2 V−1 s−1 for 6,13‐bis(triisopropylsilylethynyl)pentacene and 5,15‐bis(triisopropylsilylethynyl)tetrabenzoporphyrin, respectively. This work discloses the non‐negligible existence of solvent residuals even in high quality, long‐range ordered organic single crystals, and further provides efficient strategies to harvest the n‐type behaviors of organic semiconductor materials. Aromatic solvents with π‐conjugated structure create a coupling effect that is detrimental to electron transport. Crystals of 6,13‐bis(triisopropylsilylethynyl)‐pentacene and 5,15‐bis(triisopropylsilylethynyl)‐ tetrabenzoporphyrin grown from p‐xylene or m‐xylene exhibit a transition from p‐type to ambipolar conductance via largely reducing the amount of solvent residuals. This work offers a new strategy to harvest the n‐type behaviors for organic semiconductors.