Following the ever-expanding technological demands, printed electronics has shown palpable potential to create new and commercially viable technologies that will benefit from its unique characteristics, such as, large-area and wide range of substrate compatibility, conformability and low-cost. Through the last few decades, printed/solution-processed field-effect transistors (FETs) and circuits have witnessed immense research efforts, technological growth and increased commercial interests. Although printing of functional inks comprising organic semiconductors has already been initiated in early 1990s, gradually the attention, at least partially, has been shifted to various forms of inorganic semiconductors, starting from metal chalcogenides, oxides, carbon nanotubes and very recently to graphene and other 2D semiconductors. In this review, the entire domain of printable inorganic semiconductors is considered. In fact, thanks to the continuous development of materials/functional inks and novel design/printing strategies, the inorganic printed semiconductor-based circuits today have reached an operation frequency up to several hundreds of kilohertz with only a few nanosecond time delays at the individual FET/inverter levels; in this regard, often circuits based on hybrid material systems have been found to be advantageous. At the end, a comparison of relative successes of various printable inorganic semiconductor materials, the remaining challenges and the available future opportunities are summarized.

Printed electronics (PE) represents any electronic devices, components or circuits that can be processed using modern-day printing techniques. Field-effect transistors (FETs) and logics are being printed with intended applications requiring simple circuitry on large, flexible (e.g., polymer) substrates for low-cost and disposable electronics. Although organic materials have commonly been chosen for their easy printability and low temperature processability, high quality inorganic oxide-semiconductors are also being considered recently. The intrinsic mobility of the inorganic semiconductors are always by far superior than the organic ones; however, the commonly expressed reservations against the inorganic-based printed electronics are due to major issues, such as high processing temperatures and their incompatibility with solution-processing. Here we show a possibility to circumvent these difficulties and demonstrate a room-temperature processed and inkjet printed inorganic-oxide FET where the transistor channel is composed of an interconnected nanoparticle network and a solid polymer electrolyte serves as the dielectric. Even an extremely conservative estimation of the field-effect mobility of such a device yields a value of 0.8 cm(2)/(V s), which is still exceptionally large for a room temperature processed and printed transistor from inorganic materials.

Solution‐processed or printed n‐channel field‐effect transistors (FETs) with high performance are not reported very often in the literature due to the scarcity of high‐mobility n‐type organic semiconductors. On the other hand, low‐temperature processed n‐channel metal oxide semiconductor (NMOS) transistors from electron conducting inorganic‐oxide nanoparticles show reduced‐performance and low mobility because of large channel roughness at the channel‐dielectric interface. Here, a method to produce ink‐jet printed high performance NMOS transistor devices using inorganic‐oxide nanoparticles as the transistor channel in combination with a 3D electrochemical gating (EG) via printed composite solid polymer electrolytes is presented. The printed FETs produced show a device mobility value in excess of 5 cm2 V−1 s−1, even though the root mean square (RMS) roughness of the nanoparticulate channel exceeds 15 nm. Extensive studies on the frequency dependent polarizability of composite polymer electrolyte capacitors show that the maximum attainable speed in such printed, long channel transistors is not limited by the ionic conductivity of the electrolytes. Therefore, the approach of combining printable, high‐quality oxide nanoparticles and the composite solid polymer electrolytes, offers the possibility to fully utilize the large mobility of oxide semiconductors to build all‐printed and high‐speed devices. The high polarizability of printable polymer electrolytes brings down the drive voltages to ≤1 V, making such FETs well‐suited for low‐power, battery compatible circuitry.

Polymer‐derived, monolithic three‐dimensional nanographene (3D‐NG) bulk material with tunable properties is produced by a simple and inexpensive approach. The material is mass‐producible, and combines chemical inertness and mechanical strength with a hierarchical porous architecture and a graphene‐like surface area. This provides an opportunity to control its electron transport and mechanical properties dynamically by means of electrochemical‐induced interfacial electric fields.