A Smart Photochromic Semiconductor: Breaking the Intrinsic Positive Relation Between Conductance and Temperature

Abstract

Breaking the intrinsic rule of semiconductors that conductivity increases with increase of temperature and realizing a dramatic dropping of conductivity at high temperature may arouse new intriguing applications, such as circuit overload or over‐temperature protecting. This goal has now been achieved through T‐type electron‐transfer photochromism of one organic semiconductor assembled by intermolecular cation⋅⋅⋅π interactions. Conductivity of the viologen‐based model semiconductor (H2bipy)(Hox)2 (H2bipy=4,4′‐bipyridin‐1,1′‐dium; ox=oxalate) increased by 2 orders of magnitude after photoinduced electron transfer (a record for photoswitchable organic semiconductors) and generation of radical cation⋅⋅⋅π interactions, and fell by approximately 81 % at 100 °C through reverse electron transfer and degeneration of the radical cation⋅⋅⋅π interactions. The model semiconductor has at least two different electron transfer pathways in the decoloration process.

Excited-State Intramolecular Proton- and Inter-Polymer Charge-Transfer of Semiconducting Redox Polymers for Fe(III), Cd(II), and Hg(II) Sensing

“…Herein, σ values of Fe­(III)- FSP6 , Cd­(II)- FSP6 , and Hg­(II)- FSP6 were 2.41 × 10 –5 ( R = 7952.80 Ω), 3.86 × 10 –5 ( R = 4970.40 Ω), and 22.60 × 10 –5 S cm –1 ( R = 846.40 Ω), respectively (Figure i–k and Table ). The reduced conductivity in Fe­(III)- FSP6 compared to that of FSP6 was in good agreement with the decreased electron density on FSP6 and PL quenching in the presence of Fe­(III) . Indeed, ICT from Cd­(II)/electronic translocation between Hg­(II) and FSP6 increased the conductivities in Cd­(II)- FSP6 and Hg­(II)- FSP6 compared to that of FSP6 …”

Simple preparation of novel photochromic polyvinyl alcohol/carboxymethyl cellulose security barcode incorporated with lanthanide‐doped aluminate for anticounterfeiting applications

“…A chemical compound may undergo a photochromic transition between two distinct optical states when triggered by light. [2,3] In terms of photochromic materials, there are two types: those that switch colour under daylight and those that switch colour upon excitation with ultraviolet rays, respectively. Because of its capacity to provide numerous industrial goods, such as ophthalmic lenses, [4] electronic image displays, [5] and sensors, [6] this appealing colour-changing photochromic technology has garnered much attention in science.…”

An Ion‐In‐Conjugation‐Boosted Organic Semiconductor Gas Sensor Operating at High Temperature and Immune to Moisture

“…[6] To date, we have investigated the sensory performance of squaraines/squaramides. [2,5,7] However, owing to the plane structure and high density of zwitterions, [5] the conductivity of the latter increases significantly with temperature, [8] thereby suppressing the response signals at high temperatures. Croconates, another class of IIC materials that exhibit steric hindrance and hence prevent planar configurations [9] compared with squaraines, are expected to indicate a smaller increase in conductivity with increasing temperature.…”