New cyclopentadithiophene (CDT) linked porphyrin donors with different end-capping acceptors for efficient small molecule organic solar cells

The synthesis of two new A-π-D-π-A molecules bearing a Zn-porphyrin core donor linked through cyclopenta[2,1-b:3,4- b’]dithiophene bridges to the electron-acceptor rhodanine (SA1) or dicyanovinylene (SA2) groups is described. The optical and electrochemical properties of these compounds are investigated. The horizontal conjugation of cyclopentadithiophene between the porphyrin core and the end-capping acceptor not only effectively increases the light harvesting between the Soret and Q bands of the porphyrin unit, but also optimizes the molecular packing through linear -conjugated backbones. Compounds SA1 and SA2 are employed as donors along with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an acceptor in organic bulk heterojunction organic solar cells. After optimizing the processing of the active layer (a solvent additive and subsequent solvent vapor annealing), overall power conversion efficiencies of 6.94% and 8.19% (with low energy loss of 0.55 eV) are obtained for the organic solar cells. The use of a solvent additive and subsequent solvent vapor annealing provide enhanced nanoscale morphology and the bi-continuous interpenetrating networks in the active layer required for efficient exciton dissociation into free charge carriers and their subsequent transportation towards electrodes. This change let to higher PCE values when compared to devices based on as-cast active layers

High Photo-Current in Solution Processed Organic Solar Cells Based on Porphyrin Core A-π-D-π-A as Electron Donor Material

Two new conjugated acceptor-donor-acceptor (A-p-D-p-A) molecules with a porphyrin core linked by ethynylene bridges to two thiophene (1a) or thienylenevinylenethiophene (1b) units and both capped by N-ethylrhodanine have been synthesized. These compounds were used as the main electron donor moieties for bulk heterojunction small molecule organic solar cells (BHJ-SMOSC). The optimized devices, with PC71BM as the main electron acceptor molecule, show remarkable short circuit currents, up to 13.2 mA/cm2, an open circuit voltage of around 0.85 V, and power conversion efficiencies up to 4.3% under 100 W/cm2. The External Quantum Efficiency (EQE), Atomic Force Microscopy (AFM), hole mobility, Photo-Induced Charge Extraction (PICE) and Photo-Induced Transient Photo-Voltage (PIT-PV) were analyzed in devices based on 1a and 1b in order to account for differences in the final performance of the two molecules. The PIT-PV decays showed slower recombination kinetics for devices fabricated with 1b. Moreover, the EQE was greater for 1b and this is ascribed to the better nanomorphology, which allows better charge collection before carrier recombination takes place

Moldes quirales derivados del norborneno: aplicaciones en reacciones de metátesis

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Química Orgánica I, leída el 30-03-2009Depto. de Química OrgánicaFac. de Ciencias QuímicasTRUEpu

Efficiency Improvement Using Bis(trifluoromethane) Sulfonamide Lithium Salt as Chemical Additive in Porphyrin Based Organic Solar Cells

Two new conjugated acceptor-#960;-donor-#960;-acceptor (A-#960;-D-#960;-A) porphyrins have been synthesised using 3-ethylrhodanine (1a) or dicyanovinylene (1b) groups as acceptor units. Their optical and electrochemical properties made these materials excellent electron donor along PC71BM as acceptor for solution-processed bulk heterojunction organic solar cells. The devices based on 1a:PC71BM (1:2) and 1b:PC71BM (1:2) processed with CB showed low power conversion efficiencies (PCE) of 2.30% and 2.80%, respectively. Nonetheless, after processing the active layer using a mixture of 3 v% of pyridine additive in THF, the PCE was enhanced up to 5.14% and 6.06% for 1a:PC71BM and 1b:PC71BM, respectively. Moreover, when we used LiTFSI as chemical additive in pyridine/CB-processed 1b:PC71BM an excellent PCE of 7.63% was recorded. The effects over the film morphology and the device characteristics (Jsc, Voc and FF) by the introduction of LiTFSI are discussed