Abstract
We developed new bithiophene extended electron acceptors based on m-alkoxythenyl-substituted IDIC with three different end groups, named as IDT-BT-IC, IDT-BT-IC4F, and IDT-BT-IC4Cl, respectively. The ultraviolet absorption maximum was redshifted and the bandgap was decreased as the strong electron accepting ability of the end group increased. A differential scanning calorimetry thermogram analysis revealed that all the new acceptors have a crystalline character. Using these acceptors and a bulk heterojunction structure using PBDB-T, inverted organic photovoltaic (OPV) devices were fabricated, and their performance was analyzed. Due to the red shift of the electron acceptors, the OPV active layer particularly, which was derived from IDT-BT-IC4F, exhibited increased absorption at long wavelengths over 800 nm. The OPV prepared using IDT-BT-IC exhibited a short-circuit current density (Jsc) of 2.30 mA/cm2, an open-circuit voltage (Voc) of 0.95 V, a fill factor (FF) of 45%, and a photocurrent efficiency (PCE) of 1.00%. Using IDT-BT-IC4F, the corresponding OPV device showed Jsc = 8.31 mA/cm2, Voc = 0.86 V, FF = 47%, and PCE = 3.37%. The IDT-BT-IC4Cl-derived OPV had Jsc = 3.00 mA/cm2, Voc = 0.89 V, FF = 29%, and PCE = 0.76%. When IDT-BT-IC4F was used as the electron acceptor, the highest Jsc and PCE values were achieved. The results show that the low average roughness (0.263 nm) of the active layer improves the extraction of electrons.
Highlights
The development of photovoltaic technologies has advanced rapidly with the increasing demand for renewable energy sources to solve environmental pollution
organic photovoltaic (OPV) are prepared by constructing a bulk heterojunction (BHJ), which is an active layer comprising a blend of an electron donor (D) and electron acceptor (A), via a solution process, which provides large-area OPVs using the roll-to-roll process [4,5,6,7,8]
In contrast with the intensive research that has been conducted to obtain donor materials, the development of acceptor materials has lagged behind because fullerene derivatives are commonly used as electron acceptors
Summary
The development of photovoltaic technologies has advanced rapidly with the increasing demand for renewable energy sources to solve environmental pollution. Among the available solar cell technologies, organic photovoltaics (OPVs) stand out due to their easy processability, low cost, light weight, and flexibility [1,2,3,4,5,6]. In contrast with the intensive research that has been conducted to obtain donor materials, the development of acceptor materials has lagged behind because fullerene derivatives are commonly used as electron acceptors. Fullerene derivatives are characterized by a fully conjugated sp2 -hybridized structure, which provides excellent electron transport and acceptor capacity and promotes electron delocalization. Despite having these desirable properties, the three-dimensional structure of fullerenes limits their practical application
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