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A series of low band-gap conjugated polymers (PDTC, PDTSi and PDTP) containing electron-rich C-, Si-, and N-bridged bithiophene and electron-deficient thienopyrroledione units were synthesized viaStille coupling polymerization. All these polymers possess a low-lying energy level for the highest occupied molecular orbital (HOMO) (as low as −5.44 eV). As a result, photovoltaic devices derived from these polymers show high open circuit voltage (Vocas high as 0.91 V). These rigid polymers also possess respectable hole mobilities of 1.50 × 10−3, 6.0 × 10−4, and 3.9 × 10−4cm2V−1s−1for PDTC, PDTSi, and PDTP, respectively. The combined high Vocand good hole mobility enable bulk hetero-junction photovoltaic cells to be fabricated with relatively high power conversion efficiency (PCE as high as 3.74% for the PDTC-based device). [ABSTRACT FROM AUTHOR]

A vacuum-free solution processed hybrid dielectric composed of an anthryl-alkyl-phosphonic acid (π-σ-PA) self-assembled monolayer on an amorphous sol–gel processed hafnium oxide (HfOx) is demonstrated for low-voltage organic thin film transistors (OTFTs) on plastic substrates. The π-σ-PA/HfOxhybrid dielectric provides high capacitance (0.54 µF cm−2) and low leakage current (2 × 10−8A cm−2), and has a chemically and electrically compatible dielectric interface for evaporated and solution processed acene semiconductors. The utility of this dielectric is demonstrated by fabricating pentacene and 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-PEN) based OTFTs with operating voltages under 2 V, subthreshold slopes as low as 100 mV dec−1, and average mobilities of 0.32 cm2V−1s−1and 0.38 cm2V−1s−1, for pentacene and TIPS-PEN, respectively. [ABSTRACT FROM AUTHOR]

We report improved device performance of poly(3-hexylthiophene) (P3HT) and [6,6]phenyl C61 butyric acid methyl ester (PCBM)-based inverted bulk-heterojunction (BHJ) solar cells through the modified interface of the TiO2/BHJ with a series of carboxylic acid functionalized self-assembled monolayers (SAMs). The SAMs reduce the series resistance and improve the shunt resistance of the cell leading to increased fill factor and photocurrent density. Different aspects of device improvement can be affected depending on the nature of the SAMs. Modification with a C60-SAM shows the largest enhancement leading to a 35% improvement (η = 3.78%) over unmodified inverted devices (η = 2.80%). This SAM serves multiple functions to affect the photoinduced charge transfer at the interface to reduce the recombination of charges, passivation of inorganic surface trap states, improve the exciton dissociation efficiency at the polymer/TiO2 interface as well as a template to influence the overlayer BHJ distribution of phases, morphology and crystallinity leading to better charge selectivity and improved solar cell performance. [ABSTRACT FROM AUTHOR]