聚噻吩為一擁有高共軛系統的結構，常將其應用在有機太陽能電池材料的予體。改變其主鏈上的取代基或是原子，使這些改變對於聚合物產生的結構、吸收波長與能隙造成影響。討論這些影響是否適合用在有機異質結構太陽能電池材料上。 使用計算方法DFT/b3lyp/6-31g*，計算聚噻吩與其衍生物的結構，藉著計算的結果試著討論取代基或是原子對於聚噻吩產生的影響，其中增加聚合物的共振性將會使能隙降低，這將會有利於電子受到陽光激發而產生要遷，增加太陽能轉換成電能的機會，越多組的共軛雙鍵有利於吸收波長紅位移，吸收的波長範圍越廣，所能產生轉換為電能的波長就越多，也就有利於使太陽能轉換為電能。以及試著將衍生物的能階(HOMO、LUMO)與常用太陽能電池受體PCBM的能階比較，而這些結果將可以作為往後進行有機太陽能電池受體材料開發的參考依據。 Polythiophene belongs to a highly π-conjugated polymer. It is often used to be the donor on the bulkheterojunction organic solar cell. Changed the substituting group or atom in electron-donating molecule in BHJ solar cell can affect the structure, the absorption spectrum and the energy gap. And discussing these effects can offer the researchers to design a suitable electron-donating material which applied in BHJ solar cell. In this study, structures of the polythiophene and its derivatives are calculated used DFT/b3lyp/6-31g* method. We had discussed these substituted effects on the polythiophene and polymers with significant conjugated character will let the energy gap to be lower. This property is good for electron to be excited by sunlight and improve the solar-energy -to-electricity efficiency. Polythiophene derivatives with highly π-conjugated character will let the absorption spectrum more extensive, and also increase the opportunity to convert solar energy to electricity energy. Comparing energy level of HOMO and LUMO of the polythiophene derivatives with those of PCBM, which is often be used to be an accepter on the bulkheterojuction solar cell.These results can be the reference to researchers for developing a novel BHJ solar cell.