Influence of optical interference and carrier lifetime on the short circuit current density of organic bulk heterojunction solar cells

Based on simple analytical equations, short circuit current density （Jsc） of the organic bulk heterojunction solar cells has been calculated. It is found that the optical interference effect plays a very important role in the determination of Jsc; and obvious oscillatory behaviour of Jsc was observed as a function of thickness. At the same time, the influence of the carrier lifetime on Jsc also cannot be neglected. When the carrier lifetime is relatively short, Jsc only increases at the initial stage and then decreases rapidly with the increase of active layer thickness. However, for a relatively long carrier lifetime, the exciton dissociation probability must be considered, and Jsc behaves wave-like with the increase of active layer thickness. The validity of this model is confirmed by the experimental results.

Effects of optical interference and annealing on the performance of poly(3-hexylthiophene):fullerene based solar cells

In this paper, the effects of optical interference and annealing on the performance of P3HT：PCBM based organic solar cells are studied in detail. Due to the optical interference effect, short circuit current density （Jsc） shows obvious oscillatory behaviour with the variation of active layer thickness. With the help of the simulated results, the devices are optimized around the first two optical interference peaks. It is found that the optimized thicknesses are 80 and 208 nm. The study on the effect of annealing on the performance indicates that post-annealing is more favourable than pre-annealing. Based on post-annealing, different annealing temperatures are tested. The optimized annealing condition is 160℃ for 10 min in a nitrogen atmosphere. The device shows that the open circuit voltage Voc achieves about 0.65V and the power conversion efficiency is as high as 4.0 % around the second interference peak.

Generation and reconfiguration of interference-pattern helico-conical beams

We proposed an approach for the generation of interference-pattern helico-conical beams(HCBs)both theoretically and experimentally.The HCBs exhibiting intricate fringe structures are obtained by exploiting amplitude modulation and interference techniques.To precisely control the optical field distributions,we manipulate the azimuthal term within the helicoconical phase expression,presenting several illustrative cases that highlight the versatility of our approach.Through further combinations,more sophisticated comprehensive HCB patterns are investigated.This study deepens our knowledge about spiral-like optical patterns and paves a new avenue for potential applications,especially in the fields of particle manipulation,nanostructure fabrication,and optical metrology.

Tunable structural color of anodic tantalum oxide films

Tantalum （Ta） oxide flhns with tunable structural color were fabricated easily using anodic oxidation. The structure, components, and surface valence states of the oxide films were investigated by using gazing incidence X-ray diffractometry, X-ray photoelectron microscopy, and surface analytical techniques. Their thickness and optical properties were studied by using spectroscopic ellipsometry and total reflectance spectrum. Color was accurately defined using L＊a＊b＊ scale. The thickness of compact Ta2O5 films was linearly dependent on anodizing voltage. The film color was tunable by adjusting the anodic voltage. The difference in color appearance resulted from the interference behavior between the interfaces of air-oxide and oxide metal.

Effect of multiple parameters on the supersonic gas-jet target characteristics for laser wakefield acceleration

The supersonic gas-jet target is an important experimental target for laser wakefield acceleration(LWFA),which has great potential for driving novel radiation sources such as betatron radiation and Compton scattering gamma rays.According to different electron acceleration requirements,it is necessary to provide specific supersonic gas jets with different density profiles to generate electron beams with high quality and high repetition rates.In this study,the interference images and density profiles of different gas-jet targets were obtained through a modified Nomarski interference diagnosis system.The relationships between the gas density and back pressure,nozzle structure,and other key parameters were studied.Targets with different characteristics are conducive to meeting the various requirements of LWFA.

A high performance tunable optical filter based on cascaded polarization interference filter

A new kind of tunable optical filter is proposed for DWDM optical communication application. It is based on cascaded polarization interference filter (PIF). The period and bandpass width of each PIF are decided by its optical path difference between o-ray and e-ray (OPDOE). When their OPDOEs are proportionately designed, the tuning range and bandpass width depend on OPDOE in the first and the last PIF, respectively. The tuning range, bandpass width and crosstalk are independent each other. The crosstalk is related to the OPDOE ratios among PIFs and can be suppressed by designing the PIF's OPDOE. A set of OPDOE is suggested that are l1, 2 × l1, 22 ×l1, 23 ×l1, 24 ×l1, ..., 2N-4 × l1, 15 × 2N-7 ×l1, 10 × 2N-6 × l1 and 2N-2 ×l1 from the first to the last. This suggested OPDOEs can yield -50-dB crosstalk for any tuning range and bandpass width. The insert loss is less than 1 dB. As its loose alignment requirement, there is no limitation on cascaded PIF number. When 11 PIFs are cascaded, it can achieve 170-nm tuning range, -50-dB crosstalk, bandpass width applicable to 25-GHz channel spacing and 1 dB insert loss.

Optical bistability and multistability via multi-Raman-channel interference

We investigate the optical bistability and multistability behaviors in a closed three-level A-type atomic system. By adding a sideband on either hand of the transitions which are originally coupled by a coherent control field and a coherent probe field to disturb the two-photon resonance, bistability occurs due to two-channel interference. Increasing the sideband Rabi frequency leads to the switching from bistability to tristability. When the sideband simultaneously couples with both hands, we can easily obtain quadrastability.

Study on K^+-Na^+ Ion-Exchange Multimode Interference Optical Power Splitter

The principle of weak-confined Multimode Interference is studied, and then a 1×8 K+-Na+ ion-exchange multimode interference optical power splitter is designed and fabricated.

Optical analysis of ball-on-ring mode test rig for oil film thickness measurement

There are few experimental results available on film thickness at speeds above 5 m/s and they are almost all based on the optical ball-on-disc test rig.In contrast to the contacts in a rolling bearing,in which the lubricant in the oil reservoir distributes symmetrically,ball-on-disc contact shows asymmetry of lubricant distribution due to centrifugal effects.In order to closely imitate the contact occurring between the ball and the outer ring of a ball bearing,this study proposes an experimental model based on ball-on-glass ring contact.An optical matrix method is used to analyze the optical system,which is composed of a steel ball-lubricant-chromium-coated glass ring.Based on the optical analysis,the measurement system is improved in order to obtain a high quality interference image,which makes it possible to measure the film thickness at high-speeds conditions.