Construction of ultrathin film organic transistors is an important challenge towards deeper understanding of the charge transport mechanism and multifunctional applications. We report on precise thickness control of ultrathin films of several organic semiconductors by using a simple spin-coating approach. Ultrathin film, n-channel organic transistors with mobilities well over 1.0 cm(2) V(-1) s(-1) have been realized and their potential in high-sensitivity gas sensing and other applications is demonstrated.

We report the influence of monovalent cation halide additives on the optical, excitonic and electrical properties of CH 3 NH 3 PbI 3 perovskite. Monovalent cation halide with similar ionic radii to Pb 2+ , including Cu + , Na + and Ag + , were added to explore possibility of doping. We observed significant reduction of subbandgap optical absorption and lower energetic disorder along with a shift in the Fermi level of the perovskite in the presence of these cations. The bulk hole mobility of the additive based perovskites as estimated using the space charge limited current method exhibited an increase of up to an order of magnitude compared to the pristine perovskites with a significant decrease in the activation energy.Consequentially, enhancement in the photovoltaic parameters of additive-based solar cells was achieved.We observed an increase in open circuit voltage for AgI (~1.02 vs 0.95 V for the pristine) and photocurrent density for NaI and CuBr based solar cells (≈23 vs 21 mA.cm -2 for the pristine). This enhanced photovoltaic performance could be attributed to the formation of uniform and continuous perovskite film, better conversion and loading of perovskite as well as the enhancement in the bulk charge transport along with a minimization of disorder, pointing towards possible surface passivation.

Self-assembly of monolayers of functional molecules on dielectric surfaces is a promising approach for the development of molecular devices proposed in the 1970s. Substrate chemically bonded self-assembled monolayers of semiconducting conjugated molecules exhibit low mobility. And self-assembled monolayer molecular crystals are difficult to scale up and limited to growth on substrates terminated by hydroxyl groups, which makes it difficult to realize sophisticated device functions, particularly for those relying on n-type electron transport, as electrons suffer severe charge trapping on hydroxyl terminated surfaces. Here we report a gravity-assisted, two-dimensional spatial confinement method for bottom-up growth of high-quality n-type single-crystalline monolayers over large, centimeter-sized areas. We demonstrate that by this method, n-type monolayer molecular crystals with high field-effect mobility of 1.24 cm2 V−1 s−1 and band-like transport characteristics can be grown on hydroxyl-free polymer surface. Furthermore, we used these monolayer molecular crystals to realize high-performance crystalline, gate-/light-tunable lateral organic p–n diodes.

Incorporation of tetramethylammonium iodide into conjugated D-A polymer thin film leads to remarkable enhancement of charge mobility.

It is generally believed that the photoresponse behavior of organic field‐effect transistors (OFETs) reflects the intrinsic property of organic semiconductors. However, this photoresponse hinders the application of OFETs in transparent displays as driven circuits due to the current instability resulting from the threshold voltage shift under light illumination. It is necessary to relieve the photosensitivity of OFETs to keep the devices stable. 2,6‐diphenyl anthracene thin‐film and single‐crystal OFETs are fabricated on different substrates, and it is found that the degree of molecular order in the conducting channels and the defects at the dielectric/semiconductor interface play important roles in determining the phototransistor performance. When highly ordered single‐crystal OFETs are fabricated on polymeric substrates with low defects, the photosensitivity (P) decreases by more than 105 times and the threshold voltage shift (ΔVT) is almost eliminated compared with the corresponding thin‐film OFETs. This phenomenon is further verified by using another three organic semiconductors for similar characterizations. The decreased P and ΔVT of OFETs ensure a good current stability for OFETs to drive organic light‐emitting diodes efficiently, which is essential to the application of OFETs in flexible and transparent displays.