Two new conjugated polymers have been designed and synthesized for polymer solar cells. Both of them exhibit excellent photovoltaic properties with a power conversion efficiency as high as 4.74%. Different from the traditional linear donor-acceptor (D-A) type conjugated polymers, these newly designed polymers have a two-dimensional conjugated structure with their tunable acceptors located at the end of D-A side chains and connected with the donors on the main chain through an efficient pi-bridge. This approach provides great flexibility in fine-tuning the absorption spectra and energy levels of the resultant polymers for achieving high device performance.

We report improved device performance of poly(3-hexylthiophene) (P3HT) and [6,6]phenyl C 61 butyric acid methyl ester (PCBM)-based inverted bulk-heterojunction (BHJ) solar cells through the modified interface of the TiO 2 /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 C 60 -SAM shows the largest enhancement leading to a 35% improvement (h ¼ 3.78%) over unmodified inverted devices (h ¼ 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/TiO 2 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.

A low band gap polymer based on the copolymerization between benzodithiophene and thieno-pyrroledione units has been investigated in both conventional and inverted polymer bulk-heterojunction photovoltaic cells. High power conversion efficiencies of more than 4% in both device structures were demonstrated.

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Anthryl‐alkyl‐PA (π‐σ‐PA) self‐assembled monolayers (SAMs)/hafnium oxide (HfO2) hybrid dielectrics have been integrated into organic thin film transistors (OTFTs) to achieve operating voltages under −1.5 V. Using π‐σ‐PA SAMs on sol–gel processed HfO2, pentacene‐based OTFTs possess low subthreshold slopes (100 mV dec−1), high on–off current ratios (105–106), and hole mobilities as high as 0.22 cm2 V−1 s−1.

Two amorphous fullerenes, TPA-PCBM and MF-PCBM, have been developed as efficient electron acceptors to induce a highly stable morphology of active layer in polymer photovoltaic devices. The power conversion efficiency (PCE) of devices using both materials show no degradation, even after 10 h annealing at 150 °C.

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In this paper, we report on n-alkyl phosphonic acid (PA) self-assembled monolayer (SAM)/hafnium oxide (HfO(2)) hybrid dielectrics utilizing the advantages of SAMs for control over the dielectric/semiconductor interface with those of high-k metal oxides for low-voltage organic thin film transistors (OTFTs). By systematically varying the number of carbon atoms of the n-alkyl PA SAM from six to eighteen on HfO(2) with stable and low leakage current density, we observe how the structural nature of the SAM affects the thin-film crystal structure and morphology, and subsequent device performance of low-voltage pentacene based OTFTs. We find that two primary structural factors of the SAM play a critical role in optimizing the device electrical characteristics, namely, the order/disorder of the SAM and its physical thickness. High saturation-field-effect mobilities result at a balance between disordered SAMs to promote large pentacene grains and thick SAMs to aid in physically buffering the charge carriers in pentacene from the adverse effects of the underlying high-k oxide. Employing the appropriate n-alkyl PA SAM/HfO(2) hybrid dielectrics, pentacene-based OTFTs operate under -2.0 V with low hysteresis, on-off current ratios above 1 x 10(6), threshold voltages below -0.6 V, subthreshold slopes as low as 100 mV dec(-1), and field-effect mobilities as high as 1.8 cm(2) V(-1) s(-1).