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Abstract: Poly [3,3‴-didodecylquaterselenophene] (PQS) and poly[3,3‴-didodecylquaterselenophene-alt-didodecylquaterthiophene] (PQSQT), have been synthesized by using a Stille cross-coupling reaction. The weight-averaged molecular weights (M w ) of PQS and PQSQT were found to be 18,900Da and 22,300Da with polydispersity indices of 1.71 and 1.99, respectively. Photophysical measurements found the low bandgaps of 1.73eV for PQS and 1.86eV for PQSQT. The field-effect mobilities of PQS and PQSQT were determined to be 6.0×10−3 and 0.05cm2/Vs, respectively. The influence of the selenium and sulfur atoms in the polymer backbones were investigated with regard to device performances. The polymers were combined with the PC71BM ([6,6]-phenyl C71-butyric acid methyl ester) acceptor to fabricate bulk heterojunction solar cells with power conversion efficiencies of 0.73–2.37% under AM 1.5G (100mW/cm2) conditions. [Copyright &y& Elsevier]

Abstract: We synthesized oleic acid capped tetrapod nanocrystals of CdSe, CdTe and type II heterostructured CdTe/CdSe to investigate the effects of nanocrystal compositions and type II heterojunction on the photovoltaic properties of hybrid solar cells. The hybrid solar cell based on the blend of CdSe tetrapod nanocrystals and P3HT with a weight ratio of 6:1 showed the maximum power conversion efficiency of 1.03% under AM 1.5G condition, and the maximum incident photon to current conversion efficiency of the solar cell was 43% at 415nm. Although CdTe and CdTe/CdSe tetrapod nanocrystals showed relatively poor performance, the power conversion efficiency and the short circuit current density of the hybrid solar cell based on type II heterostructured CdTe/CdSe tetrapod nanocrystals was 4.4 and 3.9 times higher than that of the solar cell based on CdTe tetrapod nanocrystals, respectively. These results can be explained by the effects of nanocrystal compositions and type II heterojunction on the photovoltaic properties of hybrid solar cells. [ABSTRACT FROM AUTHOR]

Abstract: 2,2′,7,7′-Tetra(9,9-diethyl-9H-fluorene)-9,9′-bifluorenylidene (TFBF) was synthesized as a non-fullerene type electron acceptor for bulk-heterojunction polymer solar cells. The TFBF was synthesized from 2,7-di(9,9-diethyl-9H-fluorene)-9H-fluoren-9-one by a reductive dimerization using Lawesson's reagent. The TFBF was soluble in common organic solvents such as dichloromethane, chloroform, and 1,2-dichlorobenzene. The synthesis of TFBF was identified by 1H NMR, 13C NMR, FAB-Mass, and FT-IR, and the properties of the molecule were characterized by UV–visible absorption and fluorescence spectroscopy. The ionization potential of the TFBF solid thin film was determined by photo-electron spectroscopy, and morphology of the active layer was investigated by atomic force microscope. The measured optical band gap, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of TFBF were 2.32, −5.81, and −3.49eV, respectively. Photoluminescence (PL) spectra of P3HT solution in chloroform were measured at different TFBF concentration. The PL intensity of P3HT solution was decreased by increasing the TFBF concentration. The electron mobility of P3HT:TFBF blend film was measured to be 6.82×10−5 cm2/Vs at the electric field of 500 (V/cm)1/2. Photovoltaic devices were fabricated with the structure of ITO/PEDOT:PSS/P3HT:TFBF/LiF/Al. One of the fabricated device showed the highest V oc of 0.70V with J sc =1.20mA/cm2, FF=0.30, and PCE=0.26% at donor to acceptor composition ratio of 1:0.4. [Copyright &y& Elsevier]

Abstract: New thermally robust photoactive arylenevinylene-based conjugated polymers, poly[3,6-bis(3,7-dimethyloctyloxy)-9,9-spirobifluorenyl-2,7-vinylene] [(OC10)2-spiro-PFV] and poly[{3,6-bis(3,7-dimethyloctyloxy)-9,9-spirobifluorenyl-2,7-vinylene}-co-2-{methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene}] [(OC10)2-spiro-PFV-co-MEH-PPV], were synthesized and used to fabricate polymer solar cells. Bulk heterojunction solar cells fabricated by blending the new copolymers, spiro-PFV and (OC10)2-spiro-PFV-co-MEH-PPV, as an electron donor with the fullerene derivative, [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as an electron acceptor. The effects of electron donor to acceptor ratio, thickness of photoactive layer, and the cathode structures on the power conversion efficiency (PCE) in polymer solar cells were studied. The copolymer feed ratio was found to have a considerable effect on the PCE. The maximum PCE of 1.30% was achieved with (OC10)2-spiro-PFV-co-MEH-PPV. [Copyright &y& Elsevier]