BDT Based Polymers for High performance PSC

BDT based polymers have witnessed even more successes in organic solar cells than in organic field effect transistors. In fact, more than half of the high performance polymers for PSC with power conversion efficiency over 6% incorporate the BDT unit as part of their conjugated backbones [61]. 

Since the homopolymer of the BDT unit has a wide band gap, [22, 57] incorporation of other chromophores (usually electron-accepting moieties) as co-monomers is necessary to tune the band gap and energy levels of the BDT based copolymers. These copolymers of BDT with other chromophores can be readily prepared 

Li et al. also studied the copolymer of BDT unit with a simple vinylene linkage (P20) [66], which has an identical conjugated backbone as that of P13, but with different side chains (2-ethylhexyloxy 

P24 R = 2-ethyl hexyl, R = n-octyl P25 R = n-dodeoyl, R = 2-octyl dodecyl P26 R = 2-ethyl hexyl, R = 2-octyl dodecyl P27 R = 2-ethyl hexyl, R = 2-ethyl hexyl P28 R = 2-ethyl hexyl, R = 3,7-dlmethyl octyl 

There is one catch with the incorporation of the DTBT unit due to the excellent stacking ability of the DTBT unit [60], DTBT based polymers usually exhibit low molecular weights and limited solubility 

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