This paper reports an integration of dual band microstrip antenna with thin film amorphous silicon solar cell which creates a wearable system to harvest microwave energy. The multiple layers in the encapsulation of the thin film solar cell are used as a substrate for microstrip antenna. The rectifier and matching circuit are designed on cotton jeans material and the whole system is mechanically supported by the foam of 5 mm thick. The performance of the antenna is studied for the mechanical bending condition. The device has maintained good power conversion efficiency. The efficiency of the voltage doubler is tested by varying radio frequency power levels from −30 to10 dBm. The voltage doubler conversion efficiency at 1.85 and 2.45 GHz are 58 and 43%, respectively, for a load of 7.5 kΩ for an input power level of −5 dBm.

Single-crystalline gallium arsenide (GaAs) grown by various techniques can exhibit hillock defects on the surface when sub-optimal growth conditions are employed. The defects act as nonradiative recombination centers and limit solar cell performance. In this paper, we applied near-field transport imaging to study hillock defects in a GaAs thin film. On the same defects, we also performed near-field cathodoluminescence, standard cathodoluminescence, electron-backscattered diffraction, transmission electron microscopy, and energy-dispersive X-ray spectrometry. We found that the luminescence intensity around the hillock area is two orders of magnitude lower than on the area without hillock defects in the millimeter region, and the excess carrier diffusion length is degraded by at least a factor of five with significant local variation. The optical and transport properties are affected over a significantly larger region than the observed topography and crystallographic and chemical compositions associated with the defect.

Increasing evidence suggests that the presence of mobile ions in perovskite solar cells (PSCs) can cause a current–voltage curve hysteresis. Steady state and transient current–voltage characteristics of a planar metal halide CH3NH3PbI3 PSC are analysed with a drift-diffusion model that accounts for both charge transport and ion vacancy motion. The high ion vacancy density within the perovskite layer gives rise to narrow Debye layers (typical width ~2 nm), adjacent to the interfaces with the transport layers, over which large drops in the electric potential occur and in which significant charge is stored. Large disparities between (I) the width of the Debye layers and that of the perovskite layer (~600 nm) and (II) the ion vacancy density and the charge carrier densities motivate an asymptotic approach to solving the model, while the stiffness of the equations renders standard solution methods unreliable. We derive a simplified surface polarisation model in which the slow ion dynamics are replaced by interfacial (non-linear) capacitances at the perovskite interfaces. Favourable comparison is made between the results of the asymptotic approach and numerical solutions for a realistic cell over a wide range of operating conditions of practical interest.

In this study, the cross-section of electron-selective titanium oxide (TiO2) contacts for n-type crystalline silicon solar cells were investigated by transmission electron microscopy. It was revealed that the excellent cell efficiency of 21.6% obtained on n-type cells, featuring SiO2/TiO2/Al rear contacts and after forming gas annealing (FGA) at 350°C, is due to strong surface passivation of SiO2/TiO2 stack as well as low contact resistivity at the Si/SiO2/TiO2 heterojunction. This can be attributed to the transformation of amorphous TiO2 to a conducting TiO2−x phase. Conversely, the low efficiency (9.8%) obtained on cells featuring an a-Si:H/TiO2/Al rear contact is due to severe degradation of passivation of the a-Si:H upon FGA.

The enhanced photoresponse of commercial TiO2 (C-TiO2) nanoparticles in quantum dot (QD) sensitized solar cells, when doped with neodymium (Nd), is explored for graphene oxide–copper sulphide (GO–CuS) composite material as counter electrode. The modification of C-TiO2 and the preparation of GO–CuS were done by solid state and sonication methods respectively. The same were characterized by spectroscopy, microscopy, and cyclic voltammetry techniques. Results clearly indicate an enhanced conversion efficiency of ∼1.6 times over the undoped C-TiO2. UV and reflectance spectroscopy reveal that the dopants/defects/oxygen vacancies create midbands causing favorable surface electron states which act as electron traps suppressing recombination and the same is later detrapped leading to an efficient electron transfer. The retention of anatase phase, increase in particle size and decrease in band gap energy to visible range together with high surface area imparted by the GO to CuS in counter electrode facilitate good light harvesting and rapid enhanced electron transfer to redox system on doping. These findings make Nd–TiO2 a good photoanode material and GO–CuS a good counter electrode in QD solar cells.

This work presents a systematic study that evaluates the feasibility and reliability of local band gap measurements of Cu(In,Ga)Se2 thin films by valence electron energy-loss spectroscopy (VEELS). The compositional gradients across the Cu(In,Ga)Se2 layer cause variations in the band gap energy, which are experimentally determined using a monochromated scanning transmission electron microscope (STEM). The results reveal the expected band gap variation across the Cu(In,Ga)Se2 layer and therefore confirm the feasibility of local band gap measurements of Cu(In,Ga)Se2 by VEELS. The precision and accuracy of the results are discussed based on the analysis of individual error sources, which leads to the conclusion that the precision of our measurements is most limited by the acquisition reproducibility, if the signal-to-noise ratio of the spectrum is high enough. Furthermore, we simulate the impact of radiation losses on the measured band gap value and propose a thickness-dependent correction. In future work, localized band gap variations will be measured on a more localized length scale to investigate, e.g., the influence of chemical inhomogeneities and dopant accumulations at grain boundaries.

In this paper, we propose several solar cell designs based on metamaterials. Extensive numerical simulations of various designs with different materials are carried out. Our tests show that metamaterial solar cells are quite efficient, and over 80% and 90% absorption rates can be attained for solar spectrum and visible rays, respectively.

Carbon nanotubes (CNTs) are high aspect ratio conducting nanocylinders possessing unprecedented mechanical, thermal, optical, and electronic properties. They are ideal building blocks for use in assembling a randomly oriented, highly connected nanoporous network. When this network is deposited on top of a substrate surface as a thin film with a thickness in the range of 10–100 nm, it becomes a transparent conducting film—an ubiquitous material, currently dominated by tin-doped indium oxide (ITO). This article reviews recent progress in CNT transparent conducting films and discusses fundamental properties of CNTs important for the formation of these films, methods for CNT dispersion and assembling CNTs into transparent conducting films, properties of the CNT transparent conducting films, and issues remaining to be solved in order to make these films a commercially viable alternative to ITO.

The applicability of atom probe to the characterization of photovoltaic devices is presented with special emphasis on high efficiency III–V and low cost ITO/a-Si:H heterojunction cells. Laser pulsed atom probe is shown to enable subnanometer chemical and structural depth profiling of interfaces in III–V heterojunction cells. Hydrogen, oxygen, and phosphorus chemical profiling in 5-nm-thick a-Si heterojunction cells is also illustrated, along with compositional analysis of the ITO/a-Si interface. Detection limits of atom probe tomography useful to semiconductor devices are also discussed. Gaining information about interfacial abruptness, roughness, and dopant profiles will allow for the determination of semiconductor conductivity, junction depletion widths, and ultimately photocurrent collection efficiencies and fill factors.

A wide bandgap microcrystalline silicon film for the window layer of microcrystalline silicon thin film solar cells was obtained with very high frequency (VHF) glow discharge technology. The material was deposited on corning 7059 substrate at about 170 When H2/SiH4 was more than 100, Raman spectra showed that this material was highly crystallized, and no peak correlation with amorphous silicon was observed. This material showed strong n type before any intentional doping. We considered that the unintentional doping of oxygen and unpurified gases. The doping performance of this material was investigated by introducing B2H6 into the reacting gas. As increasing the rate of B2H6/SiH4 from zero to 0.5%, the conductivity changed from 10-1S.cm-1 (n type) to 10-8 S.cm-1 dramatically and than backed to 10-1 S.cm-1 (p type), which indicated that this material had excellent doping ability. Raman spectra also showed that the microstructure of these materials did not change obviously in this doping range. We gained the p-uc-Si:H film with thickness less than 30nm, and the conductivity was more than 10-2 S.cm-1, and crystalline volume fraction no less than 40%, the Egopt could be wider than 2.10eV. Using this p window layer in microcrystalline silicon solar cells with no ZnO rear reflection, the conversion efficiency was 8.30% (Voc=0.531V, Jsc=24.66mA/cm2, FF=63.41% ).