Low-band gap poly(di-2-thienylthienopyrazine):fullerene solar cells

Two side-chain substituted poly(di-2-thienylthienopyrazine)s (PBEHTT and PTBEHT) are used as electron donor together with $\mathrm{phenyl}\text{-}{\mathrm{C}}_{61}$ butyric acid methyl ester (PCBM) as an electron acceptor in low-band gap bulk heterojunction polymer solar cells. These low-band gap polymers absorb light up to $\sim 1\mathrm{\mu }\mathrm{m}$ . Under simulated AM1.5 conditions PTBEHT:PCBM devices provide a short circuit current of $J_{\mathrm{sc}}=3.5\mathrm{mA}∕{\mathrm{cm}}^2$ , an open circuit voltage of $V_{\mathrm{oc}}=0.56\mathrm{V}$ , and a power conversion efficiency of $\eta =1.1\%$ . Photoresponse up to $1\mathrm{\mu }\mathrm{m}$ has been observed with external quantum efficiencies exceeding 15% in the $700–900\mathrm{nm}$ region.