Photovoltaic molecules based on vinylene-bridged oligothiophene applied for bulk-heterojunction organic solar cells

We have synthesized two photovoltaic molecules（HEX-3TVT-ID and EH-3TVT-ID） based on vinylenebridged oligothiophene applied as donor for the solution-processable bulk-heterojunction organic solar cells（OSCs）. Vinylene unit was introduced as π-bridge in the oligothiophenes with 1,3-indenedione as end group and 4,4’-dihexyl-2,2’：5’,2’-terthiophene or 3’,4’-di（octan-3-yl）-2,2’：5’,2’-terthiophene as core,respectively. Due to the different substituent positions of the alkyl group relative to the vinylene unit in the terthiophene, HEX-3TVT-ID and EH-3TVT-ID show different optical and electrochemical properties, corresponding to the photovoltaic performance of the OSCs devices. The power conversion efficiency（PCE） of the OSCs based on a blend of HEX-3TVT-ID and PC71BM（1：0.8, weight ratio, 0.5% CN） reached 2.3%. In comparison, the OSCs based on the blend of EH-3TVT-ID and PC71BM in the weight ratio of 1：1 without the additive show a higher PCE of 2.7%, with a typically high VOC of 0.93 V, under the illumination of AM 1.5, 100 mW cm-2.

14.46% Efficiency small molecule organic photovoltaics enabled by the well trade-off between phase separation and photon harvesting

Small molecule organic photovoltaics(SMPVs) were prepared by utilizing liquid crystalline donor material BTR-Cl and two similar optical bandgap non-fullerene acceptor materials BTP-BO-4 F and Y6.The BTPBO-4 F and Y6 have the similar optical bandgap and different absorption coefficients.The corresponding binary SMPVs exhibit different short circuit current density(/sc)(20.38 vs.23.24 mA cm^(-2)),and fill factor(FF)(70.77% vs.67.21%).A 14.46% power conversion efficiency(PCE) is acquired in ternary SMPVs with 30 wt% Y6,companied with a JSC of 24.17 mA cm^(-2) a FF of 68.78% and an open circuit voltage(Voc) of 0.87 V.The improvement on PCE of ternary SMPVs should originate from the well trade-off between phase separation and photon harvesting of ternary active layers by incorporating 30 wt% Y6 in acceptors.This work may deliver insight onto the improved performance of SMPVs by superposing the superiorities of binary SMPVs with similar optical bandgap acceptors into one ternary cell.