In Situ LID and Regeneration of PERC Solar Cells from Different Positions of a B-Doped Cz-Si Ingot

In order to investigate the light-induced-degradation (LID) and regeneration of industrial PERC solar cells made from different positions of silicon wafers in a silicon ingot, five groups of silicon wafers were cut from a commercial solar-grade boron-doped Czochralski silicon (Cz-Si) ingot from top to bottom with a certain distance and made into PERC solar cells by using the standard industrial process after measuring lifetimes of minority carriers and concentrations of boron, oxygen, carbon, and transition metal impurities. Then, the changes of their I - V characteristic parameters (efficiency η , open-circuit voltage V oc , short-circuit current I sc , and fill factor FF ) with time were in situ measured by using a solar cell I - V tester during the 1st LID (45°C, 1 sun, 12 h), regeneration (100°C, 1 sun, 24 h), and 2nd LID (45°C, 1 sun, 12 h). The results show that the LID and regeneration of the PERC solar cells are caused by the transition of B-O defects playing a dominant role together with the dissociation of Fe-B pairs playing a secondary role. The decay of η during the 1st LID is caused by the degradation of V oc , I sc , and FF , while the increase of η during the regeneration is mainly contributed by V oc and FF , and the decay of η during the 2nd LID is mainly induced by the degradation of I sc . After regeneration, the decay rate of η reduces from 4.43%–5.56% (relative) during the 1st LID to 0.33%–1.75% (relative) during the 2nd LID.

Determination of hole diffusion length in n-GaN

The paper presents the derivation of a model for minority carriers collection based on the reciprocity theorem and its application for determination of hole diffusion length in n-GaN by means of photoluminescence. The estimated hole diffusion lengths at room temperature are 110 nm and 194 nm in the case of low and high excitation, respectively, which could be explained by saturation of non-radiative recombination centers in bulk GaN and at the surface with photogenerated carriers.

Reduction of Fluorine Diffusion and Improvement of Dark Current Using Carbon Implantation in CMOS Image Sensor

Recently, the demand of a high resolution complementary metal-oxide semiconductor (CMOS) image sensor is dramatically increasing. As the pixel size reduces to submicron, however, the quality of the sensor image decreases. In particular, the dark current can act as a large noise source resulting in reduction of the quality of the sensor image. Fluorine ion implantation was commonly used to improve the dark current by reducing the trap state density. However, the implanted fluorine diffused to the outside of the silicon surface and disappeared after annealing process. In this paper, we analyzed the effects of carbon implantation on the fluorine diffusion and the dark current characteristics of the CMOS image sensor. As the carbon was implanted with dose of 5.0 × 1014 and 1 × 1015 ions/cm2 in N+ area of FD region, the retained dose of fluorine was improved by more than 131% and 242%, respectively than no carbon implantation indicating that the higher concentration of the carbon implantation, the higher the retained dose of fluorine after annealing. As the retained fluorine concentration increased, the minority carriers of electrons or holes decreased by more Si-F bond formation, resulting in increasing the sheet resistance. When carbon was implanted with 1.0 × 1015 ions/cm2, the defective pixel, dark current, transient noise, and flicker were much improved by 25%, 9.4%, 1%, and 28%, respectively compared to no carbon implantation. Therefore, the diffusion of fluorine after annealing could be improved by the carbon implantation leading to improvement of the dark current characteristics.

MINORITY CARRIERS MOBILITY DETERMINATION IN THE BASE REGION OF N+-P-P+ SILICON SOLAR CELL UNDER EFFECTS OF IRRADIATION FLUX, TEMPERATURE AND MAGNETIC FIELD

The aim of this study is to show the influence of temperature on the relative value of the short-circuit photocurrent density obtained from an n+-p-p+silicon solar cell front illuminated with modulated polychromatic light. The solar cell was already subjected to charged particules irradiation flux (Φp) and intensity (kl,) and remained under both magnetic field (B) and temperature (T). Thus, the graphical representation of the relative value of the short-circuit photocurrent density as a function of the square of the magnetic field (B) yields to determine the slope, which is related to the mobility of minority carriers in the base. It is obtained for a back surface field silicon solar cellunder both temperature and irradiation flux of charged particules.

Synthesis and Investigation of the Properties of Organic-Inorganic Perovskite Films with Non-Contact Methods

We present the results of studies of the photoelectric properties of perovskite CH3NH3PbI2.98Cl0.02 films deposited on a glass substrate using the spin-coating method. The unit cell parameters of perovskite are determined, by using X-ray diff ractometry. It is shown that the fi lm morphology represents a net of non-oriented needle-like structures with significant roughness and porosity. In order to investigate the properties of the films obtained, we used non-contact methods such as transmission and reflection measurements and the measurements of the spectral characteristics of the small-signal surface photovoltage. The non-contact method of spectral characteristics of the small-signal surface photovoltage and the transmission method reveal information about the external quantum yield in the films studied and about the diffusion length of minority carriers in the perovskite films. As a result of this analysis, it has been established that the films are naturally textured, and their bandgap is 1.59 eV. It is shown that, in order to correctly determine the absorption coefficient and the bandgap values, the Urbach effect should be accounted for. The diffusion length of minority carriers is longer than the fi lm thickness, which is equal to 400 nm. The films obtained are promising materials for solar cells and optoelectronic devices.

Nickel and gold identification in p-type silicon through TDLS: a modeling study

In Silicon, impurities introduce recombination centers and degrade the minority carrier lifetime. It is therefore important to identify the nature of these impurities through their characteristics: the capture cross section σ and the defect level Et. For this purpose, a study of the bulk lifetime of minority carriers can be carried out. The temperature dependence of the lifetime based on the Shockley-Read-Hall (SRH) statistic and related to recombination through defects is studied. Nickel and gold in p-type Si have been selected for the SRH lifetime modeling. The objective of the analysis is to carry out a study to evaluate gold and nickel identification prior to temperature-dependent lifetime measurements using the microwave phase-shift (μW-PS) technique. The μW-PS is derived from the PCD technique and is sensitive to lower impurity concentrations. It has been shown that both gold and nickel can be unambiguously identified from the calculated TDLS curves.

A New SiC Planar-Gate IGBT for Injection Enhancement Effect and Low Oxide Field

A new silicon carbide (SiC) planar-gate insulated-gate bipolar transistor (IGBT) is proposed and comprehensively investigated in this paper. Compared to the traditional SiC planar-gate IGBT, the new IGBT boasts a much stronger injection enhancement effect, which leads to a low on-state voltage (VON) approaching the SiC trench-gate IGBT. The strong injection enhancement effect is obtained by a heavily doped carrier storage layer (CSL), which creates a hole barrier under the p-body to hinder minority carriers from being extracted away through the p-body. A p-shield is located at the bottom of the CSL and coupled to the p-body of the IGBT by an embedded p-MOSFET (metal-oxide-semiconductor field effect transistors). In off-state, the heavily doped CSL is shielded by the p-MOSFET clamped p-shield. Thus, a high breakdown voltage is maintained. At the same time, owing to the planar-gate structure, the proposed IGBT does not suffer the high oxide field that threatens the long-term reliability of the trench-gate IGBT. The turn-off characteristics of the new IGBT are also studied, and the turn-off energy loss (EOFF) is similar to the conventional planar-gate IGBT. Therefore, the new IGBT achieves the benefits of both the conventional planar-gate IGBT and the trench-gate IGBT, i.e., a superior VON-EOFF trade-off and a low oxide field.

Spatial decoupling of light absorption and reaction sites in n-Si photocathodes for solar water splitting

Metal-insulator-semiconductor (MIS) photocathodes offer a simple alternative to p-n junction photocathodes in photoelectrochemical water splitting. However, the parasitic light absorption of catalysts and metal layers in MIS junction as well as the lack of low work function metals to form a large band offset with p-Si severely limit their performance. This paper describes a MIS photocathode fabricated from n-Si, rather than the commonly used p-Si, to spatially decouple light absorption from reaction sites, which enables the majority carriers, instead of the commonly used minority carriers, to drive the surface reaction, making it possible to place the reaction sites far away from the light absorption region. Thus, the catalysts could be moved to the backside of MIS junction to avoid light-shielding. Moreover, the adoption of n-Si unlocks a variety of high work function materials for photovoltage generation. The obtained n-Si MIS photocathode exhibits an applied bias photon-to-current efficiency of 10.26% with a stability up to 300 h.

Substrate Temperature Effect on the Spectrum Emission in Superconductor Heterostructure BiPbSrCaCuZnO

This paper shows the applied voltage effect on the superconductor substrate sample. The substrate temperature (Ts) increases the activation energy of the substrate atoms. Thus, the injecting of minority carriers (holes) increased in ZnO semiconductor. These carriers recombine with electrons of 4S1 shell for Cu atom. The recombination occurs by two ways from band to band (direct recombination) or via traps (indirect recombination). The recombination mechanisms produce photons emission in the ultraviolet and visible spectrum. The calibration between voltage and temperature achieved using Variac device. The applied voltages were 60, 65, 70, and 80 Volt, and the recorded substrate temperatures were 300, 320, 350, and 400 °C, respectively.