We demonstrate an ultra-high-bandwidth Mach-Zehnder electro-optic modulator (EOM), based on foundry-fabricated silicon (Si) photonics, made using conventional lithography and wafer-scale fabrication, oxide-bonded at 200C to a lithium niobate (LN) thin film. Our design integrates silicon photonics light input/output and optical components, such as directional couplers and low-radius bends. No etching or patterning of the thin film LN is required. This hybrid Si-LN MZM achieves beyond 106 GHz 3-dB electrical modulation bandwidth, the highest of any silicon photonic or lithium niobate (phase) modulator.

Three stereochemically pure isomers and two isomeric mixtures of a solutionprocessable diketopyrrolopyrrole-containing oligothiophene ( SMDPPEH ) have been used to study the effect of 2-ethylhexyl solubilizing group stereochemistry on the fi lm morphology and bulk heterojunction (BHJ) solar cell characteristics of small molecule organic photovoltaics. The different SMDPPEH stereoisomer compositions exhibit nearly identical optoelectronic properties in the molecularly dissolved state, as well as in amorphous fi lms blended with PCBM. However, for fi lms in which SMDPPEH crystallization is induced by thermal annealing, signifi cant differences in molecular packing between the different stereoisomer formulations are observed. These differences are borne out in photovoltaic device characteristics for which unannealed devices show very similar behavior, while after annealing the RRand SS-SMDPPEH enantiomers show blue-shifted peak EQE relative to the SMDPPEH isomer mixtures. Unannealed devices made from the most crystalline stereoisomer, meso RS -SMDPPEH , are not completely amorphous, and show improved photocurrent generation as a result. Unlike the other compounds, after thermal annealing the RS -SMDPPEH devices show reduced device performance. The results reveal that the chirality of commonly used 2-ethylhexyl solubilizing chains can have a signifi cant effect on the morphology, absorption, and optimum processing conditions of small molecule organic thin fi lms used as photovoltaic device active layers.

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We report the development of efficient small molecular organic photovoltaic devices incorporating tetracene anode interfacial layers. Planar heterojunction devices employing the tetracene anode interfacial layer achieved an EQE enhancement of 150% in the spectral region corresponding to ZnPc absorption. We demonstrate that this enhancement is due to the combined effect of the tetracene layer providing exciton-blocking at the anode/donor interface and potentially an increase in the exciton diffusion length in the ZnPc layer due to increased crystallinity and more preferred molecular stacking orientation. A power conversion efficiency of 4.7% was achieved for a planar heterojunction of a modified zinc phthalocyanine based material and C60 when employing the tetracene anode interfacial layer. By utilizing a planar-mixed heterojunction structure a peak EQE of nearly 70% and a power conversion efficiency of 5.8% was achieved.