Synthesis and characterization of 2,2′-bithiophene end-capped dihexyloxy phenylene pentamer and its application in a solution-processed organic ultraviolet photodetector

Abstract

In this work a new solution processable small organic material, namely 2,2′-bithiophene end-capped dihexyloxy phenylene pentamer (BHBT₂) was synthesized, characterized and applied in the fabrication of an organic ultraviolet photodetector. The material was synthesized via Williamson etherification, bromination and Suzuki coupling. FTIR and NMR spectroscopies were recorded for BHBT₂ along with its optical, thermal and electrochemical properties. Finally, BHBT₂ was used as donor material to produce a solution-processed UV photodetector based on a BHBT₂ : PC₆₁BM organic active layer. Results showed that in forward biasing, the photodetector exhibited a photovoltaic effect with J_sc = 1.80 mA, V_oc = 0.66 V, FF = 0.30 and PCE = 0.98%, while in reverse biasing, the photodetector exhibited a fast, reversible and stable response with the highest detectivity of 1.47 × 10⁹ jones. The realization of efficient UV detection was attributed to the strong absorption of BHBT₂ and PC₆₁BM in the UV region. Hence, the BHBT₂ pentamer coupled with PC₆₁BM can be considered as a potential material to be applied in a solution-processed organic UV photodetector.