The recombination of electrons and holes in semiconducting polymer-fullerene blends has been identified as a main cause of energy loss in organic photovoltaic devices. Generally, an external bias voltage is required to efficiently separate the electrons and holes and thus prevent their recombination. Here we show that a large, permanent, internal electric field can be ensured by incorporating a...

Pure-sulphide Cu2ZnSnS4 (CZTS) thin film solar cells were prepared by a low-cost, non-toxic and high-throughput method based on the thermal decomposition and reaction of sol-gel precursor solution, followed by a high temperature sulfurization process in sulphur atmosphere, which usually gave rise to the unexpected Cu-poor and Zn-rich phase after sulfurization. In order to remove the formation o...

The paper below discusses the pros and cons of the local and global features in CBIR. To this end, four CBIR algorithms are designed and studied in terms of effectiveness. Two of them are based on local features extraction and the similarity is computed through Hausdorff distance or Euclidean distance respectively. The rest of the algorithms use global features extraction and the same two simil...

Optically multiplexed multi-carrier systems with channel spacing reduced to the symbol rate per carrier are highly susceptible to inter-channel crosstalk, which places stringent requirements for the specifications of system components and hinders the use of high-level formats. In this paper, we investigate the performance benefits of using offset 4-, 16-, and 64-quadrature amplitude modulation ...

Light trapping in subwavelength semiconductor nanowires (NWs) offers a promising approach to simultaneously reducing material consumption and enhancing photovoltaic performance. Nevertheless, the absorption efficiency of a NW, defined by the ratio of optical absorption cross section to the NW diameter, lingers around 1 in existing NW photonic devices, and the absorption enhancement suffers from...

This paper proposes the use of a transmitter based on a linear amplification with nonlinear components (LINC) architecture, in which the reconfigurable matching networks (RMNs) are included. By varying the RMN active cell number, it is possible to change the load impedance at the power amplifier (PA) output, improving the amplifier drain efficiency and therefore the efficiency of the whole syst...

This application report presents a simple power tracking technique for efficiency enhancement in CDMA RF power amplifiers. This technique involves the use of a linear-in-dB RF power detector and a DC-DC converter switch. This enhancement scheme switches the DC supply voltage, VCC, of an RF power amplifier into two different levels through a DC-DC converter. Texas Instruments RF power detector L...

The modulation characteristics of multi-section gain lever quantum dot lasers are investigated in this paper. A 20-dB enhancement in the amplitude modulation efficiency is observed in a two-section quantum dot laser. Based on rate equation analysis a novel modulation response equation is derived to describe the device dynamics. In addition the dependence of the modulation efficiency enhancement...

During holographic recording in pure (Pb5Ge3O11) and doped @(Pb12xBax)5Ge3O11# lead germanate crystals, the diffraction efficiency is transiently enhanced at the initial stage. The enhancement is studied as a function of writing-beam intensity and of dark delay time between two successive recording processes and with openor short-circuited crystal surfaces. Homogeneous pyroelectric fields that ...

The study on graphene oxide (GO) grows rapidly in recent years. We find that graphene oxide could act as the passivation material in photovoltaic applications. Graphene oxide has been applied on Si two-different-metal solar cells. The suitable introduction of graphene oxide could result in obvious enhancement on the efficiency. The simple chemical process to deposit graphene oxide makes low the...