7404 | J. Mater. Chem. C, 2017, 5, 7404--7430 This journal is © The Royal Society of Chemistry 2017 Cite this: J. Mater. Chem. C, 2017, 5, 7404 Trends in molecular design strategies for ambient stable n-channel organic field effect transistors Joydeep Dhar, a Ulrike Salzner b and Satish Patil * a In recent years, organic semiconducting materials have enabled technological innovation in the field of flexible electronics. Substantial optimization and development of new p-conjugated materials has resulted in the demonstration of several practical devices, particularly in displays and photoreceptors. However, applications of organic semiconductors in bipolar junction devices, e.g. rectifiers and inverters, are limited due to an imbalance in charge transport. The performance of p-channel organic semiconducting materials exceeds that of electron transport. In addition, electron transport in p-conjugated materials exhibits poorer atmospheric stability and dispersive transient photocurrents due to extrinsic carrier trapping. Thus development of air stable n-channel conjugated materials is required. New classes of materials with delocalized n-doped states are under development, aiming at improvement of the electron transport properties of organic semiconductors. In this review, we highlight the basic tenets related to the stability of n-channel organic semiconductors, primarily focusing on the thermodynamic stability of anions and summarizing the recent progress in the development of air stable electron transporting organic semiconductors. Molecular design strategies are analysed with theoretical investigations. 1. Introduction The last few decades have witnessed enormous progress towards realization of printed organic electronics. Research on conjugated p-systems intensified with the discovery of the sharp increase in the electrical conductivity of polyacetylene after exposing it to vapours of chlorine, bromine or iodine. Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa were awarded the Nobel Prize in Chemistry in 2000 for the discovery and development of conductive polymers. 1,2 Rapid progress in materials design and synthesis concomitant with a continuous increase in fundamental understanding has established the field of organic electronics. Commercialization of organic a Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India. E-mail: satish@sscu.iisc.ernet.in; Fax: +91-80-23601310; Tel: +91-80-22932651 b Department of Chemistry, Bilkent University, 06800 Bilkent, Ankara, Turkey Satish Patil Satish Patil is presently an Associate Professor at Indian Institute of Science, Bangalore. He received his PhD in polymer chemistry at the Bergische University of Wuppertal, Germany under the guidance of Prof. Ullrich Scherf. He then moved to the laboratory of Prof. Fred Wudl at University of California Los Angeles (UCLA) as a California Nanosystem Institute Post-doctoral fellow (CNSI). In 2006, Dr Satish Patil was appointed as an Assistant Professor in the solid state and structural chemistry unit at Indian Institute of Science, Bangalore. His research interests currently focus on synthesis of conjugated polymers and small molecules for organic electronics. Joydeep Dhar Joydeep Dhar completed his Masters in Chemistry from Indian Institute of Technology (IIT) Madras in 2009. Then in 2015, he received his PhD from Indian Institute of Science (IISc) Bangalore under the super- vision of Prof. Satish Patil. His thesis was focused on structure- property correlation of selenium based organic semiconductors. Currently he is working as Dr D. S. Kothari Postdoctoral Fellow in Jadavpur University, Kolkata, India. Received 19th December 2016, Accepted 15th June 2017 DOI: 10.1039/c6tc05467f rsc.li/materials-c Journal of Materials Chemistry C REVIEW Published on 16 June 2017. Downloaded by Bilkent University on 08/09/2017 14:33:55. View Article Online View Journal | View Issue