Charge transport mechanism in copper phthalocyanine thin films with and without traps

Abstract

We investigate the charge transport mechanism in copper phthalocyanine thin films with and without traps. Previously, charge transport in polycrystalline thin films has been widely described by the multiple trapping and release (MTR) model, without emphasizing the origin of the traps. In this work, polycrystalline organic thin films with and without traps have been grown by engineering different growth conditions. We find that the density of interface states at the grain boundaries can decide the mechanism of charge transport in organic thin films and completely different charge transport mechanisms can be observed in thin films with and without traps.

Field‐Effect Transistors Based on 2D Organic Semiconductors Developed by a Hybrid Deposition Method

“…[63] The low evaporation rate allows the subsequent gas molecules to access an energy-favorable site leading to well-ordered growth with minimum structure disorder. [64] The effect of the template on the thermally evaporated thin film was further confirmed by the transmission electron microscopy (TEM) and select area electron diffraction (SAED) analytical techniques. In the case of HTE film, as shown in Adv.…”

“…An ultraslow evaporation rate of 0.1 Å s −1 was used to avoid structural disorder . The low evaporation rate allows the subsequent gas molecules to access an energy‐favorable site leading to well‐ordered growth with minimum structure disorder …”

Ferroelectric Diode Effect with Temperature Stability of Double Perovskite Bi2NiMnO6 Thin Films

“…The cubic phase of LNO acted as an n-type semiconductor to release electrons, while the nano-crystallinity of the BNMO layer defects acted as a hole-absorbing electron [23][24][25].The Schottky emission mechanism is determined by the linear relationship of Ln(I) versus V 1/2 [26,27]. If the relationship is linear, this is due to the thermionic emission by holes, vacancies and defects [28][29][30][31][32], respectively. The restricted behavior of the interface and the hole trapping behavior are considered to be a case of the Schottky emission mechanism, as expected with linear relationship of Ln(I) versus V 1/2 for the BNMO/LNO/p-Si heterojunction (see the inset of Figure 5b).…”

Organic Heterojunction Devices Based on Phthalocyanines: A New Approach to Gas Chemosensing

“…For example, chemiresitors based on polycrystalline MPc present very high sensitivity towards oxidizing gases like NO 2 , but suffer from a prolonged recovery. Such a slow recovery was attributed to strong chemisorption of the analyte gases on the sensor surface [ 42 ], diffusion of the gas molecules in the bulk film and highly discrete pathways for the charge transport [ 13 ]. To speed up the response and recovery kinetics, different approaches have been adopted, such as sensing measurements at elevated temperature [ 43 ], use of ultrathin layer of MPc films [ 44 ] and in some cases, application of a single crystal MPc as a sensing film [ 45 ].…”

“…On the contrary, space charge region in the conventional inorganic p-n junction are highly resistive because they are composed of depletion of free charge carriers and have opposite polarity of the heterojunction in-built electric field. Since it is well known that bulk carrier transport in organic semiconductor thin films devices are slow owing to high density of traps which restrict the fast hopping of e − or h + [ 13 ] therefore, creation of a heterojunction in organic semiconductor-based devices is highly advantageous to enhance the carrier transport and thus device conductivity. The dynamics of interfacial alignments of free charges can be modulated by an external doping such as chemical doping by redox gases (e.g., NO 2 or NH 3 ), which has been exploited to develop high performances gas sensors [ 14 , 15 , 16 , 17 ].…”