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Accidentally, it was found that triphenylamine (TPA) from commercial sources shows ultralong yellow‐green room temperature phosphorescence (RTP) like commercial carbazole, which however disappears for lab‐synthesized TPA with high purity. Herein, we for the first time identify the impurity types that cause RTP of commercial TPA, which are two N, N‐diphenyl‐naphthylamine isomers. Due to similar molecular polarity and very trace amount (≈0.8 ‰, molar ratio), these naphthyl substituted impurities can be easily overlooked. We further show that even at an extremely low amount (1000000 : 1, mass ratio) of impurities, RTP emission is still generated, attributed to the triplet‐to‐triplet energy transfer mechanism. Notably, this doping strategy is also applicable to the triphenylphosphine and benzophenone host systems, of which strong RTP emission can be activated by simply doping the corresponding naphthyl substituted analogues into them. This work therefore provides a general and efficient host/guest strategy toward high performance and diverse organic RTP materials. [ABSTRACT FROM AUTHOR]

Two challenges remain for organic thermoresponsive materials; one is to develop high‐performance red‐emissive thermoresponsive materials, while another is to simultaneously achieve high contrast ratio (CR), fast and reversible thermoresponse in a single element. Herein, we not only develop a new deep‐red emissive squaraine‐based AIEgen (TPE‐SQ12) based on a pyrylium end group, which is suitable for fabricating high‐performance thermoresponsive materials, but also show an effective approach to improve both CR (∼ten times increase) and response time (less than 3 seconds), that is, molecularly dispersing AIEgen into an elastomer, attributed to the significantly expanded free volume of elastomer upon increasing the temperature that can activate the AIEgen intramolecular movements more pronouncedly. Double encryption and temperature mapping systems have been separately established by using our designed elastomer/TPE‐SQ12 film, showing the great potential for anti‐counterfeiting and temperature sensing. Finally, white emission is further achieved by co‐doping TPE‐SQ12 with cyan dye into elastomer, which enables fluorescent thermochromism for improving the temperature mapping ability. [ABSTRACT FROM AUTHOR]