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To deal with the invalidation of commonly employed series model and parallel model in capacitance–voltage (C–V) characterization of organic thin films when current injection is significant, a three-element equivalent circuit model is proposed. On this basis, the expression of real capacitance in consideration of current injection is theoretically derived by small-signal analysis method. The validity of the proposed equivalent circuit and theoretical expression are verified by a simulating circuit consisting of a capacitor, a diode, and a resistor. Moreover, the accurate C–V characteristic of an organic thin film device is obtained via theoretical correction of the experimental measuring result, and the real capacitance is 35.7% higher than the directly measured capacitance at 5-V bias in the parallel mode. This work strongly demonstrates the necessity to consider current injection in C–V measurement and provides a strategy for accurate C–V characterization experimentally.

Photomultiplier Tubes (PMTs) are widely used as the photon detector in high energy physics experiments for their fast response and high sensitivity. High precision charge measurement is usually required for PMT readout, and especially in cosmic ray experiments a large dynamic range is also demanded. This paper describes an Analog-to-Digital Converter (ADC) Application Specific Integrated Circuit (ASIC), which aims to work with a front-end analog ASIC to perform charge measurement based on the digital peak detection method. This ADC design is based on the power-efficient Successive Approximation Register (SAR) architecture, to achieve a 12-bit resolution with a sampling rate of up to 30 MS/s. Test results indicate that the Effective Number of Bits (ENOB) of this ADC is better than 9.2 bits with a sampling rate of 30 MS/s.

Time-Interleaved Analog-to-Digital Conversion (TIADC) is one of the significant technique in high speed waveform digitization systems. In our latest work, a 20-Gsps 12-bit TIADC system is designed and a series of tests are conducted on the proposed system and a broadband mismatch error correction is implemented. The test methods and results are specifically presented in this paper. The test results show that the -3dB bandwidth of the proposed system is 6 GHz and the ENOB performance is about 8.7 bits at 647 MHz and 7.6 bits at 6 GHz which is significantly enhanced by the mismatch error correction process.

An ultra-thin molybdenum(VI) oxide (MoO3) modification layer can significantly improve hole injection from an electrode even though the MoO3 layer does not contact the electrode. We find that as the thickness of the organic layer between MoO3 and the electrode increases, the hole injection first increases and it then decreases. The optimum thickness of 5 nm corresponds to the best current improvement 70%, higher than that in the device where MoO3 directly contacts the Al electrode. According to the 4,4-bis[N-(1-naphthyl)-N-phenyl-amino] biphenyl (NPB)/MoO3 interface charge transfer mechanism and the present experimental results, we propose a mechanism that mobile carriers generated at the interface and accumulated inside the device change the distribution of electric field inside the device, resulting in an increase of the probability of hole tunneling through the injection barrier from the electrode, which also explains the phenomenon of hole injection enhanced by MoO3/NPB/Al composite anode. Based on this mechanism, different organic materials other than NPB were applied to form the composite electrode with MoO3. Similar current enhancement effects are also observed.

To identify the effect of drift/diffusion current on the fill factor (FF) of organic solar cells, the correlation between FF and drift/diffusion current is studied with thickness/type of donor material, temperature and doping as the experimental parameters. Experimental results show that FF is positively related to the diffusion current. Because of the suppression of carrier diffusion, generated carriers will accumulate at the donor–acceptor interface, resulting in carrier recombination.

Self-assembled SiGe quantum rings (QRs) on Si(001) are capped with Si layers at temperatures varying from 200 to 550 °C; their shape changes after Si capping are investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The SiGe QR shape can be well preserved in the Si capping layer when the substrate temperature at Si capping is lower than 350 °C, whereas the SiGe QR shape transforms from a ring to a mound when the substrate temperature is higher than 480 °C. The SiGe QR shape could also be well preserved in the Si capping layer with an initial low temperature (300 °C) Si capping followed by a relatively high temperature (550 °C) Si capping. A comparison of the photoluminescence (PL) spectra of the SiGe QRs and the SiGe quantum dots (QDs) is also reported.