Driving nitride micro-LEDs with thin-film transistors built on solution
processable Cu-In-Se ordered defect compound semiconductors

The next-generation displays built on nitride-micro-LEDs aim to provide high brightness and resolution covering a large display area. They therefore require driving transistors in their active-matrix arrays capable of delivering a high current density within a limited footprint and can be fabricated cost-effectively over a large-area substrate. We show that ordered defect compound semiconductor CuIn 5 Se 8 , which forms regular defect complexes with defect-pair compensation, can simultaneously achieve high performance and scalable solution processability. After printing from their molecular precursors which decompose after a low temperature (370 o C) annealing, the uniform thin films of CuIn 5 Se 8 can be incorporated as the semiconductor channel of thin-film transistors, exhibiting defect-tolerant, band-like electron transport supplying an output current above 35 microamperes per micrometer, with a large on/off ratio greater than 10 6 , a small subthreshold swing of 189 ± 21 millivolts per decade, and a high field-effect mobility of 58 ± 10 square centimeters per volt per second, with excellent device uniformity and stability, superior to devices built on its less defective parent compound CuInSe 2 , analogous binary compound In 2 Se 3 , and other solution-deposited semiconductors. CuIn 5 Se 8 transistors can be monolithically integrated with carbon nanotube transistors to form high-speed and low-voltage three-dimensional complementary logic circuits with a short stage delay of 75 ns under a low supply voltage of 6 V. They can also be fabricated directly on top of GaN micro- LED arrays under a low thermal budget. Their high performance allows them to drive these micro-LEDs to a high current density above 200 amperes per square centimeter and realize high-resolution active-matrix displays with pixels per inch greater than 500.