Hybrid organic-inorganic perovskites (e.g., CH3NH3PbI3) are promising light absorbers for the third-generation photovoltaics. Herein we demonstrate a modified two-step deposition method to fabricate a uniform CH3NH3PbI3 capping layer with high-coverage and thickness of 300 nm on top of the mesoporous TiO2. The CH3NH3PbI3 layer shows high light-harvesting efficiency and long carrier lifetime over 50 ns. On the basis of the as-prepared film, TiO2/CH3NH3PbI3 heterojunction solar cells achieve a power conversion efficiency of 10.47% with a high open-circuit voltage of 948 mV, the highest recorded to date for hole-transport-material-free (HTM-free) perovskite-based heterojunction cells. The efficiency exceeding 10% shows promising prospects for the HTM-free solar cells based on organic lead halides.

Al-doped ZnO (AZO) modified ZnO nanorods have been applied in CH3NH3PbI3 perovskite solar cells, which can show a positive effect on open circuit voltage and power conversion efficiency. The average power conversion efficiency is improved from 8.5% to 10.07% and the maximum efficiency reaches 10.7%.

A simple aqueous solution route has been used to prepare mercaptoacetic acid attached CuInS2 quantum dots. Based on this material, core-shell CuInS2-Mn doped CdS quantum dot sensitized solar cells are assembled and a power conversion efficiency of 5.38% is obtained under AM1.5 (100 mW cm(-2)) illumination.

Three-dimensional (3D) imaging sensors allow machines to perceive, map and interact with the surrounding world1. The size of light detection and ranging (LiDAR) devices is often limited by mechanical scanners. Focal plane array-based 3D sensors are promising candidates for solid-state LiDARs because they allow electronic scanning without mechanical moving parts. However, their resolutions have been limited to 512 pixels or smaller2. In this paper, we report on a 16,384-pixel LiDAR with a wide field of view (FoV, 70° × 70°), a fine addressing resolution (0.6° × 0.6°), a narrow beam divergence (0.050° × 0.049°) and a random-access beam addressing with sub-MHz operation speed. The 128 × 128-element focal plane switch array (FPSA) of grating antennas and microelectromechanical systems (MEMS)-actuated optical switches are monolithically integrated on a 10 × 11-mm2 silicon photonic chip, where a 128 × 96 subarray is wire bonded and tested in experiments. 3D imaging with a distance resolution of 1.7 cm is achieved with frequency-modulated continuous-wave (FMCW) ranging in monostatic configuration. The FPSA can be mass-produced in complementary metal–oxide–semiconductor (CMOS) foundries, which will allow ubiquitous 3D sensors for use in autonomous cars, drones, robots and smartphones.

Fast optical switches have been proposed as a promising alternative to enable continual scaling of data centers with increasing size and data rates. Silicon photonics is a compelling platform for large-scale integrated photonic switches, leveraging the advanced manufacturing foundries for electronic integrated circuits. In the past decade, the port counts of silicon photonic switches have increased steadily to 128x128. Further scaling of the switch is constrained by the maximum reticle size (2~3 cm) of lithography tools. Here, we propose to use wafer-scale integration to overcome the die size limit. As a proof of concept demonstration, we fabricated a 240x240 switch by lithographically stitching 3x3 array of identical 80x80 switch blocks across reticle boundaries. Stitching loss is substantially reduced (0.004 dB) by tapering the waveguide width to 10 μm. The fabricated switch on a 4 cm x 4 cm chip exhibits a maximum on-chip loss of 9.8 dB, an ON/OFF ratio of 70 dB, and switching times less than 400 ns. To our knowledge, this is the largest integrated photonic switches ever reported. The loss-to-port count ratio (0.04 dB/port) is also the lowest.

Tin oxide (SnO 2 ) is one of the most promising electron transporters to further enhance the performance of quantum dots sensitized solar cells (QDSCs). Unfortunately, the performance of SnO 2 -based QDSCs is still poor. It was observed that surface modification toward a SnO 2 photoelectrode such as a TiCl 4 treatment is crucial to dramatically increase the performance of the devices. However, the mechanism of the TiCl 4 treatment remains poorly understood.Here, systematic studies on the photoelectrochemical properties of SnO 2 -based QDSCs were performed in order to clarify the mechanism by which the TiCl 4 treatment improves the performance of solar cells. Impendence spectroscopy results reveal that the photogenerated electrons transport in the porous SnO 2 network rather than the TiO 2 coating. Furthermore, a physical model considering the existence of monoenergetic surface states at the SnO 2 surface was used to simulate the behavior of chemical capacitance at various forward biases. The accordance between the decrease of the surface states and the recombination reduction clearly indicates that the surface states act as the recombination centers to influence the device performance, which can be well described by Marcus-Gerischer theory. These combined findings provide new understanding of the recombination mechanism of SnO 2 -based sensitized solar cells and guidelines for further improving the performance of this system.

A novel wideband microstrip band-pass filter is presented in this letter based on a quadruple-mode ring resonator, which is developed by introducing a stepped-impedance one-wavelength ring resonator (SORR) into a stepped-impedance half-wavelength resonator (SHR). In order to suppress the harmonic responses of the filter for a wide stop-band, two band-stop sections with asymmetrical -type structure are introduced. A prototype filter having 49.3% of 1 dB and 57.9% of 3 dB fractional bandwidth is fabricated with advantages of high selectivity and high out-of-band rejection. In the pass-band, the return loss is larger than 18.8 dB and at the centre frequency insertion loss is 0.6 dB. The experiments are in good agreement with the simulations.Index Terms-Quadruple-mode ring resonator, stepped impedance resonator (SIR), wideband band-pass filter (BPF).

An ultrathin AlOx layer has been deposited onto a CH3NH3PbI3 film using atomic layer deposition technology, to construct a metal-insulator-semiconductor (MIS) back contact for the hole-transporting material-free perovskite solar cell. By optimization of the ALD deposition cycles, the average power conversion efficiency (PCE) of the cell has been enhanced from 8.61% to 10.07% with a highest PCE of 11.10%. It is revealed that the improvement in cell performance with this MIS back contact is mainly attributed to the enhancement in charge collection resulting from the electron blocking effect of the AlOx layer.