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Boron-diffused samples passivated by Al2O3/TiO2 stacks with different types of TiO2 were investigated. An emitter saturation current density of 11 × 10−15 A/cm2 was obtained for Al2O3/TiO2 passivated samples with symmetrical 100 Ω/sq. boron diffusion. The surface passivation of Al2O3/TiO2 stacks was strongly impacted by the temperature, gas, and sequence during two-step annealing. In addition, the saturation current density of the Al2O3/TiO2 stacks is influenced by the TiO2 layers with an O3 treatment. Enhanced passivation performance of the Al2O3/TiO2 stacks was achieved by a combination of appropriate TiO2 capping layer and post-annealing. The results of this study provide reliable criteria for the design of thermally-stable Al2O3/TiO2 stacks on high-efficiency silicon solar cells.

The silicon solar cells achieved relatively low prices in the last years and to introduce a new structure in the PV industry, the amount of silicon per watt has to be reduced, requiring a cost-effective manufacturing process. The use of n-type solar grade silicon has the advantages of presenting higher minority carrier lifetime than p-type one and the absence of the boron-oxygen defects. The aim of this paper is to present the development of 100 μm thick n+np+ silicon solar cells with a selective p+ rear emitter formed by boron deposited by spin-on and an Al/Ag grid deposited by screen-printing. The firing temperature of Ag/Al (rear face) e Ag (front face) was optimized and the temperature of 840 °C produced the devices with higher efficiency. The solar cells presented efficiencies of 16%, achieving a low silicon consumption of 1.6 g/W, 40% lower than thick p-type devices produced by the same process.

This paper outlines the development of fully screen-printed, uniformly diffused, bifacial, n-type silicon solar cells produced using a lean processing sequence and industry-standard equipment. An average batch efficiency of 21.4% was measured at standard test conditions for an optimised bifacial cell batch (i.e. illumination on the front surface only). The results of open circuit voltage (VOC) and fill factor (FF) loss analyses are presented for select batches. By targeting reductions in the largest recombination components, optimised batch VOC was increased by 15 mV compared to the baseline case. The two largest recombination components limiting VOC in optimised devices are front contact recombination and passivated rear surface recombination. The largest FF loss components for optimised devices are the emitter sheet resistance and front contact resistance.

N-type multicrystalline silicon (mc-Si) is a promising alternative to the dominant p-type mc-Si for solar cells because it combines the cost advantages of mc-Si while benefiting from higher tolerance to transition metal contamination. A detailed understanding of the relative roles of point defect and precipitated transition metals has enabled advanced processing and high minority carrier lifetimes in p-type mc-Si. This contribution extends that fundamental understanding to Fe contamination in n-type mc-Si, helping enable processing of this material into an economical and high-performance photovoltaic device. By directly correlating micro-photoluminescence-based minority carrier lifetime mapping and synchrotron-based micro-X-ray fluorescence mapping of Fe-rich precipitates, we develop a quantitative, physical understanding of the recombination activity of Fe-rich precipitates in n - type mc-Si.

In this contribution, we demonstrate a route for efficiencies exceeding 22% with n-type multicrystalline (mc) silicon solar cells based on the TOPCon cell concept featuring a boron-diffused front side emitter and a full-area passivating rear contact. By applying a “high-performance” (HP) crystallization process with an adapted seed structure in order to obtain an optimized grain boundary area fraction, we reduce recombination losses in the HP mc-Si material to a minimum. We discuss the electrical properties of the optimized n-type HP mc-Si, which features very low material-related efficiency losses of approximately 0.5% abs and, thus, enables an efficiency potential of 22.6% with regard to a cell limit of 23.1% of the TOPCon cell concept adapted for multicrystalline silicon. Results at the device level reveal a record efficiency of 21.9%, which is the highest efficiency reported for a multicrystalline silicon solar cell. Finally, we discuss the deviations between the predicted efficiency potential and the solar cell results.

Al2O3/TiO2 stacks formed by atomic layer deposition are known to provide a high level of passivation for boron-doped silicon. In previous works, the TiO2 layer was deposited on a pre-annealed Al2O3 layer, however this stack showed passivation degradation after post-deposition annealing. This work presents an alternative to using the as-deposited Al2O3 for the Al2O3/TiO2 stack, which shows no degradation of passivation after post-deposition annealing up to 400 °C. This approach simplifies the processing, allowing continuous layer deposition, and eliminates the undesirable vacuum breaking. This simplified processing leads to better thermal stability of the Al2O3/TiO2 stacks and a low emitter saturation current density. In order to understand the underlying mechanism of surface passivation, an investigation on the effect of thermal SiO2 on the passivation of the Al2O3/TiO2 stack was performed, which indicates that the TiO2 capping layer enhances the field-effect passivation for both the Si/Al2O3 and SiO2/Al2O3 structures.

In this letter, we investigate contacts of a low work function rare-earth metal, La, and its silicides on n-Si. LaSi x / ${n}^{-}$ -Si contacts show low Schottky barrier height ( $\varphi _{b}$ ) of around 0.25–0.4 eV and promisingly low contact resistivity ( $\rho _{c}$ ) on moderately doped ${n}^{+}$ -Si. However, on highly doped ${n}^{++}$ -Si, we find $\rho _{c}$ of LaSi x near one order higher than the TiSi x control. This experiment indicates that low $\varphi _{b}$ does not guarantee low $\rho _{c}$ on highly doped substrates. We further discuss reasons behind this phenomenon.

It is shown that photocurrents along p+ and n+-type layers of a locally probed p+-n(p)-n+ silicon structure inhomogeneous in area can lead to a substantial drop of contrast of microwave photoconductivity in comparison to its intrinsic contrast. The study is performed using a model with two solar cells connected by a resistor, in which one of the solar cells is illuminated.

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An open photo-acoustic cell was used to measure the thermal diffusivity (TD) of silicon by photo-acoustic technique. The samples were heated for a period 3 h to perform sample annealing at 960, 1050, 1200 and 1300 °C in air. The TD of Si coated-silver (Ag/n-Si) was measured by fitting experimental data for the equation thermally thick in (RG) theory. For uncoated silver n-Si (single layer) samples, the TD can be obtained by fitting experimental data and by finding the intersection of the thermal thin and thermal thick (critical frequency f c ). It was found that when the annealing temperature was increased, the TD of the (n-type Si) samples was also increased. However, at a temperature of 1050 °C, the TD value of the Ag/n-Si samples was found to be 2.93 cm2 s−1. Beyond this point TD showed a degrading behavior due to a complete silver melting on silicon surface.

We present 6-inch n-type Cz-Si metal wrap through (MWT) solar cells with screen-printed and fired contacts achieving energy conversion efficiencies up to 20.4%. These so-called n-type high-performance MWT (n-HIP-MWT) structures feature different rear side configurations at the external p-type contacts with respect to the phosphorus-doped back surface field (BSF). It is shown that the alteration of the phosphorus dopant concentration at the silicon surface below the external rear p-type contacts allows for both decreasing reverse-bias-induced losses and adjusting the current flowing in reverse mode.

In this study, the influence of ambient temperature on the performance of p and n types of silicon solar cells have been investigated. The PC1D modeling software is used to simulate and analyze the photovoltaic properties of both types of silicon solar cells with the total thickness is restricted to $1\mu m$ and the ambient temperature is varied from 20 to 50°C. The simulation result exhibits the n type silicon solar cell give a better performance in term of short circuit current density compared to n type silicon solar cell. Apart from that, the conversion efficiency of silicon solar cells decrease linearly to ambient temperature due to higher recombination current. The efficiency of 5.58% is achieved for both types of silicon solar cells with ambient tempearture of 20°C.

In this work, we demonstrate a form of minority carrier degradation on n-type Cz silicon that affects both the bulk and surface related lifetimes. We identify three key behaviors of the degradation mechanism; 1) a firing dependence for the extent of degradation, 2) the appearance of bulk degradation when wafers are fired in the presence of a diffused emitter and 3) a firing related apparent surface degradation when wafers are fired in the absence of an emitter. We further report a defect capture cross-section ratio of σn/σp = 0.028 ± 0.003 for the defect in n-type. Utilizing our understanding of light and elevated temperature induced degradation (LeTID) in p-type silicon, we demonstrate that the degradation behaviors in both n-type and p-type silicon are closely correlated. In light of numerous reports on the involvement of hydrogen, the potential role of a hydrogen-induced degradation mechanism is discussed in both p- and n-type silicon, particularly in relation to the diffusion of hydrogen and influence of hydrogen-dopant interactions.

Atomic-layer-deposited titanium oxide (TiOx) is examined for the application as electron-selective full-area contact to n−type silicon solar cells. Although the surface passivation quality of TiOx-...

The evolution of irradiation-induced and hydrogen-related defects in n-type silicon in the temperature range 0 – 300 °C has been studied by deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS). Implantation of a box-like profile of hydrogen was performed into the depletion region of a Schottky diode to undertake the DLTS and MCTS measurements. Proportionality between the formation of two hydrogen-related deep states and a decrease of the vacancy-oxygen center concentration was found together with the appearance of new hydrogen-related energy levels.

We present new experimental data on light-induced degradation due to the boron oxygen defect in compensatedn-type silicon. We are the first to show that both defect components known fromp-type silicon are formed in compensatedn-type silicon. A parameterization of the injection dependent recombination activity of the slower formed defect component is established. The formation kinetics of both defect components are studied and modeled under different conditions. It is found that the same rate factors as inp-type can describe the degradation, if the actual hole concentration under illumination is taken into account. The regeneration process known to permanently deactivate boron oxygen defects inp-type is successfully applied ton-type material and the illumination stability of the regenerated state is tested and proven.

A method to dope silicon ribbons is presented. The method consists on the spraying of the ribbons with a phosphoric acid solution followed by a recrystallization in an optical heating furnace. During the sample heating, as phosphoric acid is dehydrated the resulting phosphorous compounds are either evaporated or serve as source for phosphorous diffusion. Phosphorous is efficiently incorporated in silicon by solid-state diffusion during heating and directly mixed in the melted silicon. Experimental results show significant incorporation gradients along the samples׳ length. The origin of the incorporation gradient is analysed, by testing the effect of experimental parameters such as the argon flux and the recrystallization velocity and direction. It is shown that samples recrystallized in a downward direction have homogeneous doping profiles over most of the length.

Tungsten contacts deposited on n-type 4H-SiC substrates were annealed at temperatures from 700 to 1400 °C and the phase composition of the contact layers was analyzed by TOF-SIMS technique, X-ray diffraction method and scanning electron microscopy. W 5 Si 3 and WC were characterized as the main crystalline phases formed in the contact layer after annealing at 1400 °C and crystallite size was calculated as equal to 74 nm and 73 nm, respectively. Measurements of current–voltage characteristics showed that ohmic character of the contact was obtained after annealing at the highest applied temperature 1400 °C while I – V characteristics of 1200 °C annealed contact showed limited deviation from linearity. The specific contact resistivities equal to 2.42 × 10 −5 Ω cm 2 and 2.27 × 10 −5 Ω cm 2 were achieved for 1200 and 1400 °C annealed contacts, respectively. The mechanism of ohmic contact formation was proposed.

Several industrial n-type Czochralski silicon ingots were analysed on wafer and cell levels with ECN׳s bifacial n-type solar cell process. In some of the ingots, the solar cell performance in the very top drop of about 1% absolute with respect to cell from the middle part of the ingot. These cells show typical ring shaped pattern. After receiving a post-process anneal treatment at 200 °C, the efficiency nearly completly recover. We demonstrated that the improvement is due to bulk lifetime enhancement. The recovery is stable in storage conditions, under illumination and high temperature treatments up to 600 °C. The same effect cannot be reproduced in p-type Cz silicon solar cells with similar ring shaped patterns. This indicates that the defects responsible for lifetime and efficiency degradation in wafers affected by ring patterns differ in n-type and p-type.

Porous silicon (PS) films with photocarrier-created pores (PCPs) in the films and symbiotic inverted pyramids (SIPs) at the interfaces were prepared by electrochemical etching of n-type silicon in HF ethanol solution. The effect of back side illumination, doping level of silicon, current density and HF concentration on pore and interface morphology of PS films were investigated. SEM results demonstrated that Photocarriers, generated by back side illumination, was essential to the formation of PCPs and SIPs. The moderately doped n-type silicon with P doping level in 1.1 × 10 17 −2 × 10 16 was suitable for PCP formation. The sizes of SIPs and the quantity of PCPs at their centers could be adjusted by current density when it was smaller than 25 mA cm −2 , in which the formation of PCPs competed with the growth of PS film for photocarriers and the increase of current density enhanced the growth of PS film. The formation of SIPs with four crystal planes approaching energy-stable (111) planes was believed to balance these two competitive behaviors. Since the PCPs were actually caused by photocarrier-promoted chemical etching, the HF concentration suitable for PCP formation was smaller than 20%.

Iron-acceptor (FeAc) pair association has been studied in compensated n-type silicon. A dynamic approach, based on the charge carrier recombination rates over the Fe i trap level, leads to an explanation of the observed FeAc pairing reaction in compensated n-type silicon and extends the understanding of FeAc pairing kinetics. Association kinetics was used to measure a height dependent acceptor concentration profile. Even in compensated n-type silicon good agreement with expected concentrations is found.

Minority carrier lifetime degradation induced by illumination was studied in n-type Czochralski silicon co-doped with phosphorus and boron. The recombination centre that emerges during the degradation was found to be identical to the fast-stage centre (FRC) which is known for p-Si where it is produced at a rate proportional to the squared hole concentration, p2. In n-type material where holes are excess carriers of a relatively low concentration, the time scale of FRC generation in n-Si is increased by several orders of magnitude. The generation kinetics is non-linear as a result of the dependence of p on the concentration of FRC. This non-linearity is well reproduced by simulations. An analysis of the injection level dependence of the minority carrier lifetime shows that FRC exists in 3 charge states (-1, 0, +1) possessing 2 energy levels. The recombination is controlled by both levels. FRC is identified as a BsO2 complex of a substitutional boron and an oxygen dimer. The nature of the major lifetime-degrading centre in n-Si is thus different from that in p-Si - where the dominant one (a slow-stage centre, SRC) was found to be BiO2 - a complex involving an interstitial boron.

The photoanodes with heterojunction behavior could enable the development of solar energy conversion, but their performance largely suffers from the poor charge separation and transport process through the multiple interfacial energy levels involved. The question is how to efficiently manipulate these energy levels. Taking the n-Si Schottky photoanode as a prototype, the undesired donor-like interfacial defects and its adverse effects on charge transfer in n-Si/ITO photoanode are well recognized and diminished through the treatment on electronic energy level. The obtained n-Si/TiOx/ITO Schottky junction exhibits a highly efficient charge transport and a barrier height of 0.95 eV, which is close to the theoretical optimum for n-Si/ITO Schottky contact. Then, the holes extraction can be further facilitated through the variation of surface energy level, with the NiOOH coated ITO layer. This is confirmed by a 115% increase in surface photovoltage of the photoanodes. Eventually, an unprecedentedly low onset po...

We present a brief summary about the use of ion implantation for photovoltaic applications in the past and present. Furthermore, we highlight how ion implantation might be used in the future within the fast moving field of silicon solar cells.

The electrical and physical properties of W capped ErSix on n-type Si(100), Si(111) and Si(551) surfaces are reported. The Schottky barrier heights (SBHs) are not determined by the growth of the ErSix crystal orientations, but are determined by the silicon surface orientations. And the SBHs are changed by the ratio of W capping layer thickness and ErSix thickness. These results are considered that the work function of ErSix can be controlled by the stress during the silicidation. These silicidation reactions are very important to develop the future high current drivability devices using any surface orientation.

This paper describes results of metal wrap through (MWT) cells produced from n-type Czochralski silicon wafers, and modules produced from those cells. The use of n-type silicon as base material allows for high efficiencies: for front emitter contacted industrial cells, efficiencies upto nearly 20% have been reported. MWT cells allow even higher cell efficiency, and additionally full back-contacting of the MWT cells in a module results in reduced cell to module (CTM) losses. MWT cells were produced by industrial process technologies. The efficiency of the MWT cells reproducibly exceeds the front contact cells based on the same technology by about 0.2-0.3%, and routes for further improvement are analysed. 60-cell modules were produced from both types of cells. The MWT module, based on integrated backfoil, produced 3% higher power output than the comparable tabbed front emitter contact module. In particular differences in CTM loss of current and fill factor will be presented. CTM current differences arise from the higher packing density, and lower reflectance of the backfoil, in MWT modules. CTM FF differences are related to resistive losses in copper circuitry on the backfoil versus tabs. The CTM FF loss of the MWT module was 2.2%abs lower than for the tabbed front emitter contact module. Also here the losses are analysed and routes for improvement discussed.

Co, CoNi and CoFeNi layers were formed on n-type silicon by electrodeposition method from sulfate solutions. The obtained films were characterized by Cyclic Voltammetry (CV), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS). The results show that the morphology and the stoechiometry of CoNi and CoNiFe deposits depend on several parameters (bath composition, applied potential…). The addition of sodium acetate as complexion agent in the bath leads to the formation of highly compacted and smooth films with a good adherence to the substrate.

Sulfonated polyaniline thin films are deposited on n-type silicon substrates at a rate of 1.2 nm/h. The sulfonated polyaniline/n-Si junctions were characterized by current–voltage and capacitance–voltage measurements and present Schottky barrier behavior with an energy barrier ranging from 0.9 to 1.3 eV, depending on sulfonated polyaniline film thickness and method.

Defect formation and annealing processes in n-type silicon crystals heat-treated at temperatures from 550 to 1000°C for a short time and then gamma-irradiated in a 60Co source or electron-irradiated (E = 4 MeV) at room temperature have been studied using Hall effect measurements. The results demonstrate that the preheat treatment (PHT) has an insignificant effect on the energy spectrum and generation efficiency of major defect species. At the same time, PHT results in enhanced annealing of radiation-induced defects, accompanied by the formation of additional electrically active centers. PHT is assumed to activate transition-metal impurities (fast diffusers in silicon), which then interact with radiation-induced defects.

The growth of well-defined regular columnar macropores under front-side illumination on medium doped n-type silicon has been investigated. The various morphologies observed, with branched or columnar pores, differ from those reported so far on substrates of both higher and lower resistivities. Unlike stated by the macropore growth model, current density is found to influence the pore growth rate. These observations indicate that, under the conditions used in this work, the pore growth is at the border between meso- and macroporous mechanism. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Dynamic nuclear polarization of the 29Si nuclei due to the “solid-effect” was observed clearly after saturation of the phosphorus electron paramagnetic resonance lines in three kinds of silicon crystals containing different amount of the 29Si isotope (1%, 4.7%, and 99.3%). Maximal enhancement (E) of the room-temperature 29Si nuclear magnetic resonance signals E ≈ 605 was obtained at the temperatures of 10–14 K in silicon containing 1% of the 29Si isotope. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The annealing of the cluster damage after fast neutron and high energy /spl pi//sup +/-pion irradiations is studied employing the deep-level transient spectroscopy (DLTS) method. The clusters consist mainly of divacancies. However, other unidentified defects contribute to the signal of the single negative charge state of the divacancy. The unidentified defects are located in the cluster region. Strain and deformation fields are assumed to change the emission parameters of the defects in the cluster region resulting in a distribution of energy states. Simulations of the DLTS signals, which take into account an exponential density distribution of energy states, were carried out. During annealing a decay of divacancies and the other unidentified defects is observed.

Aluminum-added silver paste (Ag/Al paste) has been used for p+ emitter of n-type solar cells. The electrical losses due to shunting and recombination caused by the paste in the cells have been reported to originate from huge metallic spikes due to the aluminum. However, whether the aluminum actually induces the losses has not been clarified yet. In this study, the "floating contact method" is applied to aluminum-free silver (Al-free Ag) paste to investigate the effects of aluminum extraction from the Ag/Al paste and to understand how the aluminum principally induces the losses for the p+ emitter. Furthermore, the interfacial morphology between the Al-free Ag paste and p-type silicon is investigated. The Ag paste itself creates tiny crystallites for the p+ emitter, resulting in shunting and recombination. The result indicates that the aluminum addition to Ag paste is not the main reason for the electrical losses in the n-type solar cells.

We measure very high minority-carrier lifetimes exceeding 20 ms on 1.4-Ω cm n-type Czochralski silicon wafers passivated using plasma-assisted atomic-layer-deposited Al2O3 on both wafer surfaces. The measured maximum effective lifetimes are surprisingly high as they significantly exceed the intrinsic lifetime limit previously reported in the literature. We are able to measure such high lifetimes by realizing an exceptionally homogeneous Al2O3 surface passivation on large-area samples (12.5 × 12.5 cm2). The importance of the homogeneous passivation is demonstrated by comparison with samples of locally reduced passivation quality.

Theory of n-type silicon longitudinal and transverse piezoresistance coefficients in the case of uniaxial pre-strain state along [100] crystallographic axis is presented. Numerical calculations for various impurity concentrations in a range of 1·1016 – 1·1020 cm−3 are performed. It has been shown that compressive pre-strain state of the piezoresistor can increase the longitudinal piezoresistance coefficient on 60 %.

Using specially “designed” electrolytes, it is possible to obtain macropores even in highly doped n-type silicon (0.020–0.060 Ωcm) without illumination. Based on predictions of the “current-burst-model” [phys. stat. sol. (a) 182, 63 (2000), this issue], HF-containing electrolytes were systematically modified with strongly oxidizing components and evaluated with respect to their ability to produce macropores. Well developed macropores with depths up to 10 μm and pore diameters between 200 nm and 2 μm could be obtained in several cases. The macropore nucleation starts with a facetting of the surface on {111} planes.