During the last decade

conjugated polymers have attracted much attention because of their important applications in polymeric light-emitting diodes

photovoltaic cells

and field-effect transistors. Siloles are conjugated organometallic molecules that possess low-lying LUMO associated with the σ

*

-π

*

conjugation (arising) from the interaction between the σ

*

orbital of two exocyclic σ-bonds on the ring silicon and the π

*

(orbital) of butadiene moiety. As a result

siloles exhibit high electron acceptability and fast electron mobility. So far siloles have been utilized as efficient electron-transport materials and light-emitting materials in the construction of electroluminescence devices

and increasing interests have been paid to silole-base polymers. Benzothiadiazole and its derivatives are excellently narrow band-gap comonomers for modifications of known conjugated polymers

which can tune emission color of copolymers with enhanced emissive efficiency due to (efficiently) intramolecular and intermolecular energy transfer. Up to now

to the best of our knowledge

there is no report of a copolymer derived from a silole and benzothiadiazole or its derivative

and applications of a silole-based polymer in photovoltaic cells have not been investigated. Two novel alternating copolymers PS-BT and PS-DBT derived from 1

1-diethynyl-2

3

4

5-tetraphenylsilole and 2

1

3-benzothiadiazole (BT) or 4

7-bis(2-thienyl)-2

1

3-benzothiadiazole (DBT) were prepared by palladium-catalyzed coupling reactions. UV-Vis absorption

photoluminescence (PL) and photovoltaic behaviour of the copolymers were also investigated. PS-DBT showed wider and stronger absorption in the visible light region

compared with PS-BT. Along with the increasing of solution concentration

red-shifting of the peak positions of PL spectra were found for the two copolymers. Photovoltaic cells were fabricated with a configuration of ITO/PEDOT/copolymers:PCBM(1:4)/Ba/Al. The open-circuit voltages for PS-BT and PS-DBT were 0.50 and 0.40 V

respectively. The fill factors for PS-BT and PS-DBT were 24% and 33%

respec-(tively). Under the illumination of an AM1.5 solar light simulator

the energy conversion efficiencies for PS-BT and PS-DBT were 0.009% and 0.032%

respectively.