Abstract
Organic heterostructures have emerged as highly promising transducers to realize high performance gas sensors. The key reason for such a huge interest in these devices is the associated organic heterojunction effect in which opposite free charges are accumulated at the interface making it highly conducting, which can be exploited in producing highly sensitive and faster response kinetics gas sensors. Metal phthalocyanines (MPc) have been extensively studied to fabricate organic heterostructures because of the large possibilities of structural engineering which are correlated with their bulk thin film properties. Accordingly, in this review, we have performed a comprehensive literature survey of the recent researches reported about MPc based organic heterostructures and their application in gas sensors. These heterostructures were used in Organic Field-Effect Transistor and Molecular Semiconductor—Doped Insulator sensing device configurations, in which change in their electrical properties such as field-effect mobility and saturation current in the former and current at a fixed bias in the latter under redox gases exposure were assessed to determine the chemosensing performances. These sensing devices have shown very high sensitivity to redox gases like nitrogen dioxide (NO2), ozone and ammonia (NH3), which monitoring is indispensable for implementing environmental guidelines. Some of these sensors exhibited ultrahigh sensitivity to NH3 demonstrated by a detection limit of 140 ppb and excellent signal stability under variable humidity, making them among the best NH3 sensors.
Highlights
Over the recent few decades, organic semiconductors have drawn tremendous attention in the development of electronic devices such as organic light-emitting diodes (OLEDs) [1], organic photovoltaics (OPVs) [2], organic field-effect transistors (OFETs) [3], organic lasers [4], memory devices [5] and chemical sensors [6]
Metal phthalocyanines (MPc) heterostructures heterostructures have beenbeen widely studied, their their devices employing have widely studied, applications in gas chemosensing are rather scarce despite plenty of reviews of OFET gas sensors based applications in gas chemosensing are rather scarce despite plenty of reviews of OFET gas sensors based on homostructures [12,59,64,65]
We have demonstrated that chemosensing devices incorporating MPc-based organic heterostructures have drawn significant research interest for redox gases detection over the past 10 years
Summary
Over the recent few decades, organic semiconductors have drawn tremendous attention in the development of electronic devices such as organic light-emitting diodes (OLEDs) [1], organic photovoltaics (OPVs) [2], organic field-effect transistors (OFETs) [3], organic lasers [4], memory devices [5] and chemical sensors [6]. The creationadvantageous of a heterojunction in organic semiconductor-based devices is highly advantageous dynamics of interfacial alignments of free charges can be modulated by an external doping such as to enhance the carrier transport and device conductivity. Change of metal center has a strong influence on electronic properties, such as lutetium-bis-phthalocyanine has shown unique radical nature and is the first intrinsic molecular semiconductor reported with exceptionally high free charge carriers density (5 × 1016 cm−3 ), electronic conductivity (5 × 10−5 Ω−1 cm−1 ) [21] and very low band gap (0.5 eV) Owing to such fascinating electrical properties and stabilities of MPc thin films, these molecular semiconductors have stimulated a lot of interests in organic heterojunction-based gas sensors. A concise conclusion and a perspective regarding the enhancement and efficient utilization of organic heterojunction effects in gas sensing devices are given
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