We report the synthesis and bulk heterojunction photovoltaic performance of the first dithienogermole (DTG)-containing conjugated polymer. Stille polycondensation of a distannyl-DTG derivative with 1,3-dibromo-N-octyl-thienopyrrolodione (TPD) results in an alternating copolymer which displays light absorption extending to 735 nm, and a higher HOMO level than the analogous copolymer containing the commonly utilized dithienosilole (DTS) heterocycle. When polyDTG-TPD:PC(70)BM blends are utilized in inverted bulk heterojunction solar cells, the cells display average power conversion efficiencies of 7.3%, compared to 6.6% for the DTS-containing cells prepared in parallel under identical conditions. The performance enhancement is a result of a higher short-circuit current and fill factor in the DTG-containing cells, which comes at the cost of a slightly lower open circuit voltage than for the DTS-based cells.

The detailed characterization of solution‐derived nickel (II) oxide (NiO) hole‐transporting layer (HTL) films and their application in high efficiency organic photovoltaic (OPV) cells is reported. The NiO precursor solution is examined in situ to determine the chemical species present. Coordination complexes of monoethanolamine (MEA) with Ni in ethanol thermally decompose to form non‐stoichiometric NiO. Specifically, the [Ni(MEA)2(OAc)]+ ion is found to be the most prevalent species in the precursor solution. The defect‐induced Ni3+ ion, which is present in non‐stoichiometric NiO and signifies the p‐type conduction of NiO, as well as the dipolar nickel oxyhydroxide (NiOOH) species are confirmed using X‐ray photoelectron spectroscopy. Bulk heterojunction (BHJ) solar cells with a polymer/fullerene photoactive layer blend composed of poly‐dithienogermole‐thienopyrrolodione (pDTG‐TPD) and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) are fabricated using these solution‐processed NiO films. The resulting devices show an average power conversion efficiency (PCE) of 7.8%, which is a 15% improvement over devices utilizing a poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL. The enhancement is due to the optical resonance in the solar cell and the hydrophobicity of NiO, which promotes a more homogeneous donor/acceptor morphology in the active layer at the NiO/BHJ interface. Finally, devices incorporating NiO as a HTL are more stable in air than devices using PEDOT:PSS.

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Significant progress in power conversion efficiencies and stabilities of polymer solar cells has been achieved using semiconducting metal oxides as charge extraction interlayers. Both n-and p-type transition metal oxides with good transparency in the visible as well as infrared region make good Ohmic contacts to both donors and acceptors in polymer bulk heterojunction solar cells. Their compatibility with roll-to-roll processing makes them very attractive for low cost manufacturing of polymer solar cells. In this review, we will present the recent results on synthesis and characterization of these metal oxides along with the device performance of the solar cells using these metal oxides as interlayers.

Interface recombination induced by the defect states in zinc‐oxide‐nanoparticle‐based electron extraction layer is reported as a significant loss‐mechanism of photocurrent collection. By choosing appropriate UV–ozone treatment conditions on the zinc oxide layer, inverted polymer solar cells show reduced interface recombination and thus improved power conversion efficiencies of up to 8.1%.

truefalse2016-03-16T23:02:09

It is a great challenge to fabricate piezoresistive sensors that possess high elasticity, large-area compliance, and excellent detectability to satisfy both extremely tiny and large human activity monitoring. Herein, a novel and facile strategy is reported to manufacture highly elastic channel crack-based gold@PU sponge piezoresistive material. The elastic 3D conductive network is successfully prepared by gold ion sputtering, and channel cracks are skillfully designed on the 3D sponge skeletons. Such novel structure makes these fabricated sensors are capable of monitoring both tiny and large human motions, which originate from the nanocrack joint sensing mechanism and physical contact of conductive interconnected network. Meanwhile, our sensors possess excellent elasticity, fast response time (9 ms), and ultralow detection limit (0.568 Pa), as well as good reproducibility over 1000 cycles. The desirable elasticity of channel crack-based gold@PU sensor is comparable to recently reported pressure sensors, together with advantages of reliable fabrication and large-area compliance, makes them attractive in various electronic devices, for example, biological health monitoring, sport performance monitoring, and man-machine interfaces.

The VOC loss in several polymer-fullerene solar cells is determined. Based on these data, a major source of photovoltage loss is attributed to the low dielectric constants of the polymers. Such loss is close to zero if the dielectric constant of the polymer-fullerene blend is close to 5.