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The commonly used donor material poly(3-hexylthiophene) (P3HT) confines the power conversion efficiency (PCE) in P3HT-based polymer solar cells due to its relatively large bandgap of $1.9 eV and the resultant limited absorption wavelength region of less than 650 nm. In this communication, the highly efficient up-conversion (UC) material NaYF 4 :2% Er 3+ , 18% Yb 3+ , converting near-infrared radiation into green and red emissions, is introduced into a P3HT/P3HT:[6,6] phenyl C 61 butyric acid methyl ester (PC 61 BM) bulk heterojunction solar cell, referred to as a "bilayer cell", to compensate for the nonabsorbable wavelength region of P3HT. With an optimal UC doping concentration of 11.7% (weight ratio of UC to P3HT) in the P3HT matrix, the short-circuit current density and PCE for UC-doped bilayer cell are as high as 10.89 mA cm À2 and 3.62%, about 16.6% and 10.7% higher than the P3HT/ P3HT:PC 61 BM bilayer cell and 22.4% and 16.4% higher than the standard P3HT:PC 61 BM bulk heterojunction one, respectively, although the fill factor in the UC-doped bilayer cell shows a slight decrease. The research result demonstrates that both the emission and the scattering of UC nanoparticles are beneficial to the enhancement of the solar cell's electrical performances.

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Published by the AIP Publishing Articles you may be interested inA 70 kV solid-state high voltage pulse generator based on saturable pulse transformer Rev. Sci. Instrum. 85, 024708 (2014); 10.1063/1.4864194 Completely explosive ultracompact high-voltage nanosecond pulse-generating system Rev. Sci. Instrum. 77, 043904 (2006); 10.1063/1.2168674 High-voltage pulse switching hardware for electro-optic studies of conducting aqueous solutions Rev. Sci. Instrum. 73, 3080 (2002);

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Pulsed power research for military and civil applications has been conducted at the China Academy of Engineering Physics (CAEP) for more than 50 years. The pulsed power research activities include development of pulsed power components, such as different kinds of high-voltage switches, series of pulsed power sources and pulsed X-ray machines, highcurrent accelerators for Z-pinch and flash X-ray radiography, as well as medical application and electromagnetic launch. The most recent progress of pulsed power research at CAEP will be presented.

By utilizing the radio-frequency metal-oxide-semiconductor field-effect transistor switch, the multi-stage stacked printed circuit board Blumlein lines, and the induction voltage adder, a voltage generator with MHz repetition rates and nanosecond duration was designed and fabricated. The shunting current of the multi-stage stacked Blumlein lines, which consists of the coupling current at the load ends and the leakage current at the switch ends, is clarified. The circuit simulation and experiment of the three-stage stacked Blumlein lines are carried out; the result shows that the experiment and simulation agree well. The five-stage IVA prototype is designed for generating voltage pulses of ∼10 kV in amplitude and 8–11 ns in duration with MHz burst repetition rates. The voltage generator with MHz repetition rates and nanosecond duration demonstrated an important application prospect to reduce the electron beam initial emittance of the high energy accelerator.