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New quinoxaline and selenophene based benzodithiophene bearing conjugated polymers for photovoltaic applications

Çalışkan, Meriç
The current research trends have greatly focused on the development of new low band gap conjugated polymers featuring alternating donor-acceptor unities to achieve remarkable power conversion efficiencies for OPV devices. For this purpose, a series of new quinoxaline and selenophene based BDT bearing conjugated polymers namely P1, P2 and P3 were synthesized using Stille cross coupling reaction. The 2-(2-Octyldodecyl)selenophene ring was attached to 4th and 8th positions of phenyl ring in BDT to obtain donor moiety and three different quinoxaline moieties as acceptors were introduced into the BDT backbone. After completion of synthesis of D-A polymers, their structures were identified with H1 NMR spectroscopy and their molecular weights were examined with GPC. Moreover, electrochemical, spectroelectrochemical kinetic and thermal studies of polymers were carried out. The photovoltaic properties and blend film morphologies of resulting polymers were also investigated. The synthesized polymers were utilized as donor segment in active layer and they were combined with PC71BM ([6,6]-phenyl C71-butyric acid methyl ester) acceptor to fabricate bulk heterojunction solar cells, that produced highest power conversion efficiencies as following: 2.36% for P1, 2.07% for P2 and 2.45% for P3 under AM 1.5 G (100 mW/cm2) conditions.