  Air-stable semiconducting inks suitable for complementary logic are key to
create low-power printed integrated circuits (ICs). High-performance printable
electronic inks with two-dimensional materials have the potential to enable the
next generation of high performance, low-cost printed digital electronics. Here
we demonstrate air-stable, low voltage (< 5 V) operation of inkjet-printed
n-type molybdenum disulfide (MoS2) and p-type
indacenodithiophene-co-benzothiadiazole (IDT-BT) field-effect transistors
(FETs), estimating a switching time of {\tau} ~ 3.3 {\mu}s for the MoS2 FETs.
We achieve this by engineering high-quality MoS2 and air-stable IDT-BT inks
suitable for inkjet-printing complementary pairs of n-type MoS2 and p-type
IDT-BT FETs. We then integrate MoS2 and IDT-BT FETs to realise inkjet-printed
complementary logic inverters with a voltage gain |Av| ~ 4 when in resistive
load configuration and |Av| ~ 1.36 in complementary configuration. These
results represent a key enabling step towards ubiquitous long-term stable,
low-cost printed digital ICs.
