Solution-Processed LiF-Doped ZnO Films for High Performance Low Temperature Field Effect Transistors and Inverted Solar Cells

This paper reports that high performance metal oxide thin film transistors (TFTs) can be achieved by using LiF-doped ZnO thin films processed from aqueous solution. It was found that LiF doping at an appropriate amount enhanced the oxide film carrier concentration. The TFTs based on the 10 mol % LiF-doped ZnO thin films annealed at 300 °C revealed a good device performance with an average electron mobility of 8.9 cm(2) V(-1) s(-1) and a high on/off current ratio of 4 × 10(7), superior to the devices based on the nondoped ZnO TFTs (1.6 cm(2) V(-1) s(-1)). Even when annealed at 150 °C, the device still showed good transistor operation with an electron mobility of 0.54 cm(2) V(-1) s(-1). The inverted bulk heterojunction solar cells based on P3HT:PCBM blend system fabricated using 10 mol % LiF doped ZnO as electron selective layer showed higher power conversion efficiency (η = 3.3%) than that from undoped ZnO thin films (η = 2.94%) due to enhanced short circuit current (Jsc = 10.55 mA/cm(2)). Our results suggest that LiF incorporation can be a useful technique to produce high performance and low temperature solution-processed oxide TFTs and interface layer for solar cells.