Deep Ultraviolet Phototransistor Based on Thiophene-Fluorobenzene Oligomer with High Mobility and Performance

Deep ultraviolet(UV)photodetectors have important applications in the industrial and military fields.However,little research has been reported on organic phototransistors(OPTs)in the deep ultraviolet range.Here,a novel organic semiconductor containing a small torsion angle and lowπ-conjugation 2,2':5',2"-terthiophene groups,oF-PTTTP,is designed and synthesized,which exhibits high carrier mobility and unique deep ultraviolet response.Accordingly,an OPT based on oF-PTTTP single crystal shows high responsivity to deep-UV light.The photodetectors achieve high photoresponsivity(R)of 857 A/W and detectivity(D*)of 3.2×10^(15)Jones under 280 nm light illumination(only 95 nW·cm^(–2)).To the best of our knowledge,280 nm is the deepest detection wavelength reported for organic phototransistors and this work presents a new molecule design concept for organic phototransistors with deep-UV detection.

Thermally-enhanced photo-electric response of an organic semiconductor with low exciton binding energy for simultaneous and distinguishable detection of light and temperature

Simultaneous and distinguishable detection of external stimuli such as light and temperature is of great interest for a variety of scientific and industrial applications.Theoretically,an organic semiconductor with low exciton binding energy,low thermal activation energy and good charge transporting property produces thermally enhanced photo-electric response in organic phototransistors(OPTs),which thus provides an ideal and effective way to realize the simultaneous and distinguishable detection of temperature and light.However,there is no report on such a kind of organic semiconductor until now.Herein,we designed and synthesized a narrow band gap organic small molecule semiconductor 2,5-bis(2-butyloctyl)-3,6-bis(5-(4-(diphenylamino)phenyl)thiophen-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione(DPP-T-TPA)with low exciton binding energy(about 37 meV)and small activation energy(about 61 meV)for distinct thermal-dependence of charge carrier and exciton.The low exciton binding energy enables the semiconductor to exhibit strong thermal dependence of exciton dissociation,which contributes to the thermally-enhanced photo-electric response.Furthermore,the low thermal activation energy produces the weak thermal dependence of charge transport,which avoids the disturbance of thermally-modulated charge transport on photo-electric response.Benefiting from these two features,phototransistors based on DPP-T-TPA show great potential in simultaneous and distinguishable detection of light and temperature,which represents a novel and efficient way for bifunctional detection.