Solution coating of organic semiconductors offers great potential for achieving low-cost and high-throughput manufacturing of large-area and flexible electronics. However, the solution processability of semiconducting small molecules for fabricating uniform and reliable thin-film devices poses challenges due to the low viscosities of small-molecule solutions. Here, we report a universal approach employing a primer template (PT) to enhance the spreadability of small-molecule solutions on silicon wafers, enabling the spin-coating fabrication of uniform thin films composed of millimeter-scale grains with complete large-area coverage and well-ordered molecular packing. Using PT, we fabricated organic thin-film transistors (OTFTs) using solutions containing various small molecules such as rubrene and 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene. The device yield of all fabricated OTFTs is consistently 100% while achieving a high average mobility of 1.62 cm 2 V −1 s −1 with a device-to-device variation of 7.7% measured in ambient air condition. In addition, the utilization of PT resulted in a batch-to-batch variation of 12.5% in device performance over dozens of OTFT devices. The key industrial manufacturing metrics, such as device yield, reproducibility, and performance uniformity of the PT OTFTs, are among the best for devices fabricated using solution spin-coating techniques.
Molecular solution with the metal-thiourea complex is a facile and effective route for Cu 2 SnS 3 (CTS) thin film deposition . However, its stability is still challenging due to flexible metal salts precursors. Here we report a strategy to enhance the stability of the Cu–Sn–S molecular solution that use bivalent Sn to suppress the oxidation of the S 2- of thiourea via the redox reaction . The self-stabilizing mechanism has been carefully revealed by the systematic experiments and confirmed by the spontaneous reaction process of metal-thiourea system. It demonstrates that Sn with a low valence state weakens the transfer of lone pair electrons from thiourea to Cu 2+ and Sn 4+ ions, alleviating the sulfur precipitates from thiourea oxidation because of the easily reducible character of Sn 2+ ion. The solution with Sn 2+ antioxidant additive can be stored for a long time under air ambient, which is then spin-coated and sulfurized with Sn powder compensation. The uniform CTS thin film with composition control is finally achieved and delivers a device efficiency of 1.15%. This work provides a guide on stabilizing the solution precursor for chalcogenide thin film deposition.
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