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This study reports on the electronic properties of industrial phosphorus-doped n-type silicon ingots for photovoltaic applications grown using the Recharged Czochralski method. The electronic quality is assessed via carrier lifetime measurements, both directly on the ingots and on passivated wafers, and via implied open-circuit (i V O C), and implied maximum power point (i V M P P) voltages. The wafers are studied in the as-grown state, and after various high temperature steps, including Tabula Rasa , phosphorus diffusion gettering, and boron diffusion. The material exhibited very high bulk quality, with bulk lifetimes up to 8 ms at an injection level of 5 × 10 14 cm − 3 , and with i V O C (1-sun) values up to 750 mV , prior to any high temperature processing. A Tabula Rasa step did not significantly improve the wafer quality, indicating a low presence of oxygen-related defects in this material, consistent with the low interstitial oxygen content of below 5 × 10 17 cm − 3 . However, phosphorus diffusion gettering improved the wafer quality, especially towards the tail end of each ingot, and at lower injection levels near maximum power point. Phosphorus diffusion gettering increased the i V O C (1-sun) of the wafers by around 5 mV , approaching the Auger limit. Additionally, a boron diffusion step had minimal impact on the bulk lifetimes. Overall, our findings suggest that these RCz-grown n-type wafers exhibit very high quality, approaching the Auger limit near open-circuit, and are well-suited for high-efficiency solar cells without the need for additional high-temperature processing. • Assessing the material quality of n-type RCz industrial ingots, both directly on the ingot and on passivated wafers. • Bulk lifetimes of up to 8 ms and i V O C (1-sun) values up to 750 mV. • Low interstitial oxygen content of below 5 × 10 17 cm − 3 , low presence of oxygen-related defects. • Improvement of the wafer quality after gettering, particularly towards the bottom of each ingot, nearing the Auger limit. • No significant degradation after boron diffusion. [ABSTRACT FROM AUTHOR]

In this paper, electronic semiconductor characterization using reverse-back procedure was applied to different photoacoustic responses aiming to find effective ambipolar diffusion coefficient and a bulk lifetime of the minority carriers. The main idea was to find the small fluctuations in investigated parameters due to detecting possible unwanted sample contaminations and temperature variations during the measurements. The mentioned procedure was based on the application of neural networks. Knowing that in experiments the contaminated surfaces of the sample can play a significant role in the global recombination process that we are measuring and that the unintentionally introduced defects of the sample crystal lattice could vary the carrier lifetime by several orders of magnitude, a method of PA signal adjustment by the reverse-back procedure is developed, based on the changes of the carrier electronic parameters. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the characteristics of different neural networks trained on the same theoretical database of n-type silicon photoacoustic signals. By adding different levels of random Gaussian noise to the training input signals, two important goals were achieved. First, the optimal level of noise was found which significantly shortens the training networks with minimal loss of accuracy of its predictions. Second, the termination criteria of networks training were activated to avoid overtraining, i.e., networks generalization was performed. A networks efficiency analysis was performed on both theoretical and experimental photoacoustic signals, resulting in a selection of one neural network that is optimal to the performance requirements of the real experiment. It is indicated that the application of such trained networks is more reliable on thicker semiconductors, whose thickness is greater than the value of the carrier diffusion length in the investigated sample. [ABSTRACT FROM AUTHOR]

Task of studies is a development of the structure and way of fabrication of a photocell capable to take a radiation or in near infrared range of the spectrum (0,9–1,4) micron, or in the field of (0,5–1,4) micron. Way of fabrication and results of studies of photoelectric features of two spectrum photocells based on two Schottky barrier contacts PtSi-n-Si (or PdSi-nSi), situated on opposite parties silicon plate, are сonsidered. It is shown that the explored photocell can be used for the transformation of the energy of the radiation in the electrical energy at room temperature in two ranges: or in near infrared region of the spectrum (0,9–1,4) micron, or in the field of (0,5–1,4) micron. This characteristic of the designed photocell will allow to increase its application. Photocell possesses a simple structure and technology with a time of its fabrication in the interval (2,5–3) of the hour.

This paper proposes a new hybrid temperature compensation system for doped silicon-based piezoresistive 3D stress sensors. The developed compensation system integrates a temperature sensor, placed in close proximity to the stress sensing rosettes, with the artificial neural networks (ANNs). In this work, the n-type circular piezoresistor featured over (111) silicon plane was employed to capture the local temperature variations, within the sensing chip. The extracted temperature changes, along with the resistance changes, are fed, as inputs, to the ANNs to compensate the temperature effect on the acquired signals for more accurate stress measurement. The proposed compensation system was experimentally evaluated while extracting stress applied up to 60 MPa at different temperatures within a range from 0 °C to 50 °C. The developed system was successfully able reduce the maximum full scale error, obtained from using only a temperature sensor for compensation, by ~55%. The new system has merit since it has the capability to compensate for both resistance and sensitivity, for 3D stress sensor, with no need for additional circuitry. Moreover the employed temperature sensor shares the same thermal environment with the stress sensing rosette. [ABSTRACT FROM AUTHOR]

Thin film of oriented crystalline intrinsic polysilicon films were grown on alkali-free borosilicate glass substrate using hot-wire chemical-vapor-deposition (HWCVD) technique. A layer as a source of phosphorus dopant on top of intrinsic polysilicon films were introduced in two different approaches: (i) spinon one-micrometer-thick phosphorus dopant and (ii) phosphorus ion implantation. We investigate the possibility of dopant diffusion, activation, and annealing, using the irradiation of 1064 nm wavelength infrared laser. The annealing is performed under various conditions. The laser power and scan speed are varied to ensure the suitable laser annealing condition. We carry out resistivity measurements to validate the laser annealing process. For structural investigation, we use several characterization techniques, such as scanning electron microscopy, high-resolution X-ray diffraction, photoluminescence spectroscopy, and confocal Raman spectroscopy measurements. We use optical transmission spectra for determining optical characteristics of the film. The electrical measurement shows that the phosphorous-doped n-type polysilicon films are suitable as an emitter layer in photovoltaic device. [ABSTRACT FROM AUTHOR]

This paper introduces the possibility of the determination of optical absorption and reflexivity coefficient of silicon samples using neural networks and reverse-back procedure based on the photoacoustics response in the frequency domain. Differences between neural network predictions and parameters obtained with standard photoacoustic signal correction procedures are used to adjust our experimental set-up due to the instability of the optical excitation source and the state (contamination) of the illuminated surface. It has been shown that the changes of the optical absorption values correspond to the light source wavelength fluctuations, while changes in the reflexivity coefficient, obtained in this way, correspond to the small effect of the ultrathin layer formation of SiO2 due to the natural process of surface oxidation. [ABSTRACT FROM AUTHOR]

In this paper, a developed n-type piezoresistive three dimensional (3D) stress sensor with full temperature compensation is presented. The proposed sensing rosette benefits from the stress insensitivity of the full-circular n-type piezoresistor, oriented over (111) silicon plane, to detect only temperature changes for compensation. Moreover, the unique behavior of shear piezoresistive coefficient ($\pi _{{{44}}}$) of n-Si is utilized to construct a piezorestive stress sensing rosette over (111) silicon plane that is capable of extracting 3D stress components. A prototype stress sensing chip was microfabricated to test the capability of the developed sensing rosette to accurately extract stress applied on structures at different thermal environments. The fabricated sensing chip was subjected to different mechanical loads using a loading rig with four-point bending fixture. The testing was carried out over a temperature range of 0–50 °C. The results showed that the proposed sensing chip has the capability of capturing the stress applied at different temperatures. Also, the developed sensing rosette showed less sensitivity to the uncertainty in piezoresistive coefficients’ values compared to the other developed 3D piezoresistive stress sensors. [ABSTRACT FROM AUTHOR]

Abstract The effects of doping level, illumination intensity and temperature on the regeneration kinetics and dynamics of BO defects in compensated n-Si have been investigated. The regeneration rate, corrected with interstitial oxygen concentration and average injection level, is almost constant in n-type samples with different doping levels under the same regeneration condition. It is proportional to the average injection level during regeneration when the doping level and temperature are fixed. In comparison with previous studies using n-type silicon, the regeneration completeness is significantly improved, especially in samples with net doping levels higher than 1 × 1016 cm−3, due to the higher regeneration temperature and more stable surface passivation films. The remaining incompleteness is mostly dominated by the occupation of the annealed state (as opposed to the activated state). For rapid and complete regeneration, the optimal condition is applying high illumination intensities at around 200°C. Highlights • Unambiguous highly complete regeneration of boron-oxygen-related defects is demonstrated in compensated n-type silicon lifetime samples with a large range of doping levels. • The effects of the illumination intensity, temperature and doping level on the regeneration kinetics and dynamics of boron-oxygen defects in n-type silicon are systematically studied and analysed. • For rapid and complete regeneration, the optimal condition is applying high illumination intensities at around 200 °C. [ABSTRACT FROM AUTHOR]

In this paper, a new temperature transducer using full-circular n-type piezoresistor over (111) silicon plane is proposed as an accurate solution for local temperature compensation for piezoresistive three-dimensional (3-D) stress sensors. Analytical study, in this paper, showed that the proposed n-type full-circular piezoresisor over (111) has near-zero response under 3-D state of stress. As an experimental verification, a test device with n-type piezoresistive stress sensing elements oriented over (111) plane at 0° and 90° to crystallographic direction $[ {\bar{1}10} ]$ was microfabricated to test the capability of the proposed temperature compensator. The test device was subjected to a uniaxial load up to 50 MPa using a loading rig with four-point bending fixture. The testing was performed over a temperature range of 0–50 °С. The results showed that the proposed temperature transducer has a linear response to temperature excitation. The fabricated transducer is capable of accurately capturing the local temperature changes with maximum absolute error of ±0.8 °С. This compensation system is advantageous for piezoresistive stress/strain sensors, since the temperature transducer has the same thermal environment with the stress/strain-sensing rosette. Moreover, this technique does not require additional circuitry on the sensing device itself. [ABSTRACT FROM AUTHOR]

Abstract In this paper, bifacial n- type silicon wafer solar cells with a front boron-diffused emitter and a rear phosphorus-diffused back surface field are investigated. The cell structure is abbreviated as n FAB (n -type Front and Back Contact). Three different process flows are evaluated for the fabrication of n FAB cells: (1) process flow with a silicon nitride diffusion mask deposited by plasma-enhanced chemical vapour deposition (PECVD), (2) process flow with a silicon oxynitride diffusion mask also deposited by PECVD, and (3) process flow using single-sided atmospheric pressure chemical vapour deposition (APCVD), without diffusion masks. An average batch efficiency of 21.3% was measured (front side illumination only) for all three n FAB process flows. However, the reverse bias I-V characteristics are observed to be remarkably different and dependent on the process flow, especially with regards to the masking processes. For process flow 1 that uses a silicon nitride PECVD mask, the reverse bias I-V characteristics are poor with a severe breakdown occurring at − 5 V and a reverse current of 18 A at −10 V. Process flow 2 with a silicon oxynitride PECVD mask leads to significantly improved reverse characteristics with a reverse current of 1 A at −10 V. For the APCVD process flow without diffusion masks, excellent reverse bias characteristics are observed with a reverse current of only 3 mA at −10 V. Reverse-biased electroluminescence imaging is used to determine the breakdown regions of the cells for the different process flows and to analyse the impact of the diffusion masking step on the cells' breakdown characteristics. Highlights • Investigation of n -FAB (Front and Back contact) silicon wafer solar cells with a diffused boron front emitter and phosphorus back surface field. • Three different process flows are evaluated for the fabrication of n-FAB solar cells. • All groups have an identical batch average efficiency of 21.3%. However the reverse I-V characteristics were observed to be remarkably different. • Investigates breakdown sites in n-type cells by studying the impact of the manufacturing process flow, specifically with regards to the use of PECVD dielectrics as diffusion masks. [ABSTRACT FROM AUTHOR]

Abstract Passivation quality of poly-Si contacts with different phosphorus doping concentration were investigated in this study. Intrinsic poly-Si layers were deposited by LPCVD on a tunnel oxide surface, followed by n + poly-Si doping and hydrogenation. For lightly doped poly-Si contacts with phosphorus concentration of 2.1 × 10 19 cm − 3 , higher temperatures and longer times increased iV OC achieving maximum value of 734 mV, as poly-Si grain size increases from 13 nm to 40 nm. However, for heavily doped poly-Si contacts with phosphorus concentration of 1.1 × 10 20 cm − 3 , iV OC decreased from 731 mV to 696 mV as annealing time increased from 10 to 60 min because Auger recombination rate increased from 9.3 fA / cm 2 to 21.6 fA / cm 2 as phosphorus in-diffusion occurs. The contact resistance of poly-Si contacts was also investigated to achieve a high fill factor. Finally, a poly-Si/SiO x /c-Si passivated contact solar cell using a poly-Si contact on the back and boron diffused emitter on the front was fabricated. As a result, high efficiency of 21.1% solar cell was achieved with V OC of 665 mV, J SC of 40.6 mA/cm2, and fill factor of 78.3%. Highlights • Passivation quality of poly-Si passivated contacts is controlled by annealing temperature, time and doping concentration. • Passivation quality is improved by grain size growth. • Phosphorus in-diffusion decreases passivation quality because of increased Auger recombination. • High-quality poly-Si passivated contact with i V O C of 734 mV was achieved by large grain size and low in-diffusion. • Cell efficiency of 21.1% was achieved using improved poly-Si passivated contact. [ABSTRACT FROM AUTHOR]

Strain has been integrated into many silicon devices, as it has an essential impact on carrier mobility and crystal symmetry. Those parameters respond differently under both biaxial and uniaxial, so their effect needs to be quantified to successfully employ the strain engineering in different silicon applications. As an extended step toward utilizing strain in enhancing the sensitivity and the temperature independency of a 3-D stress sensor, the effect of uniaxial transverse strain onto the piezoresistive (PR) coefficients of heavily doped n-type silicon will be experimentally characterized. A new design was developed to apply the transverse tensile and compressive uniaxial stresses onto the silicon substrate using a highly compressive nitride layer. This stressing technique was integrated with six PR elements rosette to fully calibrate the PR coefficients, where unstrained, tensile, and compressive strained PRs are fabricated within the same chip to accurately quantify the strain impact. Four-point bending, stress-free temperature, and hydrostatic test were used to typically measure the PR coefficients. Strain values of 0.065% and 0.083% $\varepsilon $ were achieved locally using both the tensile and compressive stressors, respectively. Under this level of strain, the typical result shows opposite impact for both the tensile and compressive transverse strains on the longitudinal and transverse PR coefficients. Moreover, an increase up to 80% can be achieved for the pressure coefficient of heavily doped n-type silicon due to the compressive transverse strain. [ABSTRACT FROM AUTHOR]

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 σ n /σ p = 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. [ABSTRACT FROM AUTHOR]

A one‐step method to obtain boron emitters for n‐type solar cells based on the use of boron tribromide (BBr3) as a dopant source is developed. During this study several experimental parameters are varied. It is observed that besides the diffusion temperature, the nitrogen gas flux and the BBr3 bubbler temperature have a significant impact on the obtained emitter properties. Using the adequate experimental conditions a homogenous boron emitter without boron rich layer (BRL), a sheet resistance of 77 Ω sq−1 and a dark saturation current <100 fA cm−2 is obtained. [ABSTRACT FROM AUTHOR]

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The p-type spherical silicon solar cell is a candidate for future solar energy with low fabrication cost, however, its conversion efficiency is only about 10%. The conversion efficiency of a silicon solar cell can be increased by using n-type silicon semiconductor as a substrate. This study proposed a new method of neutron transmutation doping silicon (NTD-Si) for producing the n-type spherical solar cell, in which the Si-particles are irradiated directly instead of the cylinder Si-ingot as in the conventional NTD-Si. By using a ‘screw’, an identical resistivity could be achieved for the Si-particles without a complicated procedure as in the NTD with Si-ingot. Also, the reactivity and neutron flux swing could be kept to a minimum because of the continuous irradiation of the Si-particles. A high temperature engineering test reactor (HTTR), which is located in Japan, was used as a reference reactor in this study. Neutronic calculations showed that the HTTR has a capability to produce about 40 t/EFPY of 10 Ω cm resistivity Si-particles for fabrication of the n-type spherical solar cell. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum‐alloyed back‐junction is a novel concept for low‐cost and industrially feasible n‐type silicon solar cells. In this paper, we fabricated industrially high‐efficiency solar cells based on both uncompensated and compensated n‐type silicon. Moreover, we measured the impact of temperature on the photovoltaic performance of aluminum‐alloyed back‐junction n‐type silicon solar cells. Compared with conventional front‐junction solar cells, the back‐junction silicon solar cells have a lower absolute temperature coefficient especially for moderate carrier diffusion lengths which is attributed to distinctive spectral response, stronger dependence on carrier diffusion lengths, and incomplete ionization of aluminum. In addition, the lowest absolute temperature coefficient is obtained on this type of aluminum‐alloyed back‐junction solar cell when the compensated silicon is used as the base layer. These results suggest that aluminum‐alloyed back‐junction solar cells especially based on the compensated silicon can generate more electricity at a high temperature, and therefore, as a cost‐effective production of silicon solar cells, this type of solar cells have a very good potential for actual outdoor application. This work is highly relevant to the development of an advanced process for the achievement of low‐cost, high‐efficiency, commercially viable silicon‐based solar cells. [ABSTRACT FROM AUTHOR]

It is generally taken for granted that the bulk minority carrier lifetime in uncompensated phosphorus-doped silicon (Si) wafers is stable under illumination. In contradiction with this long-time belief, we report on a fast and significant lifetime degradation under light soaking for Czochralski wafers sampled from the top ingot end. We demonstrate that defect formation also proceeds during carrier injection by forward biasing Si heterojunction solar cells made from such wafers, suggesting a carrier-induced degradation rather than merely light-induced. The involved bulk defect is shown to preferentially form at the wafer center, where double Thermal Donors are in high concentration. The role of Thermal Donors is investigated further and the obtained preliminary results support their involvement in the reported carrier-induced degradation. [ABSTRACT FROM AUTHOR]

The main goal of the solar cell industry is to reduce the production cost so that the photovoltaic technology can be competitive with other kinds of electricity generation. The combination of the use of n-type silicon to obtain higher efficiency devices and thinner wafers can be an alternative for reducing cost. The aim of this work is to present the analysis of different metal pastes to form the electrical contact grid of the boron doped face in solar cells fabricated in thin wafers of n-type Czochralski-growth solar grade silicon. The p+nn+ and n+np+ structures were studied. By comparing metal pastes of Ag, Ag/Al and Al, we concluded that the latter enabled the manufacture of the more efficient solar cells. The aluminum metal paste has to be screen-printed before the deposition of the dielectric film of TiO2 because it does not etch-through the thin film during firing of metal pastes. By using aluminum paste deposited on the boron doped face, the solar cells with n+np+ and p+nn+ structures reached efficiencies of 13.4% and 12.6%, respectively, values relatively low due to the use of thin solar grade silicon wafers and the absence of surface passivation. [ABSTRACT FROM AUTHOR]

Numerical and experimental sensitivity analyses in this paper indicate that the accuracy of a silicon multi-element piezoresistive (PR) stress sensor can be dramatically influenced by the microfabrication non-uniformity and the uncertainties in the values of the PR coefficients and the thermal coefficient of resistance (TCR). The results showed that errors as large as 70% FS or more, in the extracted stress values, may be obtained due to uncertainty of about 2.5% in the values of PR coefficients. This paper aims to evaluate the capabilities of the artificial neural network (ANN) to eliminate the error in stress measurement, due to the fabrication non-uniformity within wafer, wafer-to-wafer, and batch-to-batch, for multi-element PR sensing rosettes. In this paper, sensing chips from two different batches were integrated in building the ANN and testing its performance. The proposed calibration technique employs the neural network fitting Toolbox in MATLAB to generate a two-layer feed-forward network, with sigmoid hidden neurons and linear output neurons. Three different configurations of calibration were designed to test the generalization abilities of the ANN in capturing the in-plane stress components exerted on the silicon chip. The results showed that ANN is capable of accurately predicting the stresses applied to the sensing chip with maximum stress error of 1.5% FS with no need for individual, expensive, and time-consuming calibration process for each sensor. [ABSTRACT FROM PUBLISHER]

In this study we investigate metal spike formation of screen-printed Ag/Al pastes during contact firing in an infrared belt furnace and its influence on the characteristics of n-type bi-facial silicon solar cells. The boron emitters are formed in a co-diffusion step using boron doped PECVD layers. It is demonstrated that the formation of Ag/Al spikes results in strong FF and V OC losses limiting the solar cell efficiency. This can mainly be attributed to an increased saturation current density of the second diode which is strongly increasing with increasing set peak firing temperature. A detailed scanning electron microscopy analysis reveals that this j 02 increase can be attributed to an increasing area density and depth of the Ag/Al spikes for increasing peak firing temperatures. [ABSTRACT FROM AUTHOR]

We present 6-inch n-type Cz-Si metal wrap through (MWT) solar cells with screen-printed and fired contacts achieving energy conversion efficiencies of 20%. In order to decrease the occurrence of leakage currents under forward operation to a minimum after applying reverse bias load, the structuring of the rear side phosphorus doping in the area of the external p-type contacts is necessary. The fabrication of these so-called n-type high-performance MWT+ (n-HIP-MWT+) solar cells is considerably simplified by using laser processes to locally structure the rear side phosphorus doping. The n-HIP-MWT+ cells fabricated with laser structuring achieve the same peak energy conversion efficiency of 20% as conventionally fabricated ones, which are manufactured using an elaborate inkjet-based masking process prior to phosphorus diffusion. The loss of cell efficiency after reverse biasing is decreased to – 0.1% abs independent of the structuring method, and is three times smaller than the one observed for cells without structuring of the phosphorus doping. [ABSTRACT FROM AUTHOR]

The use of plasma immersion ion implantation (PIII) is a relevant approach for the development of advanced solar cells technologies at lower cost (€/W p ). In this paper, we report on the development of homogeneous boron (B) doping of n-type crystalline silicon (cSi) substrate by the PIII technique. Using diborane (B 2 H 6 ) as gas precursor, various doping profiles were identified fitting the requirements for boron-doped emitters in n-type PERT solar cells. Particularly, saturation current density (J 0e ) of 50 fA/cm 2 were achieved on symmetrical samples for a 94 Ω/sg textured B-emitter passivated with SiO 2 /SiN stack. Bifacial n-type Passivated Emitter Rear Totally-diffused (n-PERT) solar cells were fabricated using the PIII technology and conversion efficiencies up to 19.8% on 239 cm 2 Cz-Si wafers were obtained. As a consequence, these results indicate that PIII can compete with beamline technology but will have lower running cost. It is therefore a promising technology to create high efficiency cSi solar cells. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Laser-fired contacts to n-type crystalline silicon were developed by investigating novel metal stacks containing Antimony (Sb). Lasing conditions and the structure of metals stacks were optimized for lowest contact resistance and minimum surface damage. Specific contact resistance for firing different metal stacks through either silicon nitride or p-type amorphous silicon was determined using two different models and test structures. Specific contact resistance values of 2-7 mΩcm2 have been achieved. Recombination loss due to laser damage was consistent with an extracted local surface recombination velocity of ~20 000 cm/s, which is similar to values for laser-fired base contact for p-type crystalline silicon. Interdigitated back contact silicon heterojunction cells were fabricated with laser-fired base contact and proof-of-concept efficiencies of 16.9% were achieved. This localized base contact technique will enable low cost back contact patterning and innovative designs for n-type crystalline solar cell. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Studying encapsulated n-type interdigitated back contact (IBC) solar cells with front floating emitter (FFE) we observe a power degradation mechanism which behaves similar to the PID-p degradation for n-type IBC solar cells with front surface field described in [1] or for bifacial n-type solar cells in [2]. This power drop is not shunt-related and arises as loss of short circuit current and open circuit voltage in analogy to the findings in [1]. The power degradation occurs when biasing FFE-IBC minimodules with negative potential against the ground and can be fully regenerated by reversing the polarity of the bias potential. The susceptibility to PID for our IBC minimodules depends on the encapsulation material to higher or lesser extent; until now no material was identified which can totally prevent PID. Bifacial IV measurements and EL recordings let us conclude that the PID we observe is non-local and causes a homogenous degradation of the front surface of the solar cell. Silvaco Atlas simulations show that a total loss of surface passivation is not sufficient to explain the effect. [ABSTRACT FROM AUTHOR]

We have investigated fine grained polycrystalline silicon thin films grown by direct chemical vapor deposition on oxidized silicon substrates. More specifically, we analyze the influence of the doping type on the properties of this model polycrystalline silicon material. This includes an investigation of defect passivation and benchmarking of minority carrier properties. In our investigation, we use a variety of characterization techniques to probe the properties of the investigated polycrystalline silicon thin films, including Fourier Transform Photoelectron Spectroscopy, Electron Spin Resonance, Conductivity Activation, and Suns-Voc measurements. Amphoteric silicon dangling bond defects are identified as the most prominent defect type present in these layers. They are the primary recombination center in the relatively lowly doped polysilicon thin films at the heart of the current investigation. In contrast with the case of solar cells based on Czochralski silicon or multicrystalline silicon wafers, we conclude that no benefit is found to be associated with the use of n-type dopants over p-type dopants in the active absorber of the investigated polycrystalline silicon thin-film solar cells. [ABSTRACT FROM AUTHOR]

We developed a high efficiency N-type PERT (Passivated Rear Totally Diffused) bifacial structure based on B and P ion implantation doping, SiO 2 passivation and conventional screen-printing metallization. Two process flows were compared: a “co-anneal” process and a process using separated anneals for B and P activation. We highlight the impact of the variations of the B- emitter and P- BSF profiles on the solar cells performance. The impact of the boron implantation dose was studied allowing to optimize this parameter. Concerning the BSF, two temperature ranges were studied for the P activation leading to very different BSF profiles. A shallower profile enables to reach high implied Voc while keeping low contact resistivity. The overall optimization was integrated into a simplified and industrial process flow on large area Cz-Si solar cells (239cm 2 ). An average efficiency of 19.7% was reached using the “co-annealing” process. The efficiency in this case was limited by a low PFF. This limitation was solved using the “separated anneal” process where an average efficiency of 20.2% was obtained on a 15 cells batch with a 20.5% champion cell. [ABSTRACT FROM AUTHOR]

We observe minority carrier lifetime degradation in n -type wafers with boron-diffused surface and SiO 2 /SiN passivation when exposed to illumination or thermal aging. This degradation is not observed on control wafers with phosphorus-diffused surfaces and identical passivation under the same treatment. Boron-diffused wafers with Si-rich SiN or Al 2 O 3 passivation do not degrade either. Both boron-diffused layer and SiO 2 /SiN are thus necessary to observe this degradation. Experiments on different aging conditions indicate that the degradation is due to a thermal effect accelerated by injection of excess carriers. [ABSTRACT FROM AUTHOR]

A boron-rich layer (BRL) is formed during the boron diffusion process in fabricating crystalline Si solar cells. We investigated the structural, optical, and electrical characteristics of BRL in n-type silicon. A boron emitter was formed using the BBr3 liquid source in a tube furnace at 950°C. BRL had an amorphous phase. The peak concentration of boron in BRL was over 1023atoms/cm³. BRL consisted of boron, silicon, and oxygen. The oxygen atoms seemed to have caused the formation of amorphous phase. BRL showed the refractive indices of 1.5-2.0, and the contact resistance of 0.8mΩcm². [ABSTRACT FROM AUTHOR]

The first order piezoresistance coefficients are examined in the n-type silicon structures with different dimensionality of electron gas: bulk crystal, quantum film (well) and quantum wire. The detail research involves quantum kinetic approach to calculation of the kinetic coefficients (conductivity, mobility, concentration) of electrons in the strained and unstrained states. As scattering system were adopted ionized impurities, longitudinal acoustic phonons and surface roughness. Detailed studies have been carried out for dependences of electron mobility and piezoresistance coefficients on confining dimensions. An alternative explanation is proposed for origin of the giant piezoresistance effect in n-type silicon nanostructures. Comparison of the obtained results shows not only qualitative but even sufficient quantitative agreement with experimental data. [ABSTRACT FROM AUTHOR]

Abstract: Bilayer coatings deposited by atomic layer deposition are shown to simultaneously achieve excellent passivation and low reflectivity, suitable for application on the front side of high-performance n-type Si solar cells. We designed and fabricated bilayer coatings of 10nm Al2O3 followed by a top layer of either 50.5nm TiO2 or 52.5nm ZnS. The bilayers have absolute reflectivity nearly 2% lower than state-of-the-art silicon nitride anti-reflection coatings. They passivate both highly doped p-type emitter surfaces and also low-doped p-type Si. For a B-doped emitter with sheet resistance of 159Ω/sq on n-type Si, the Al2O3/TiO2 coating has a low emitter saturation current density J 0,e of 38fA/cm2, while Al2O3/ZnS has 52fA/cm2. On low-doped p-type Si wafers, passivation using either coating resulted in minority carrier lifetimes above 1ms, corresponding to surface recombination velocities below 10cm/s. [Copyright &y& Elsevier]

ABSTRACT We present the integrated development of back-contacted solar cells and an adequate module interconnection for a high-efficiency photovoltaic module. We report on a large area (125 × 125) mm2 back-junction back-contact n-type solar cell metallized with aluminum having a total area conversion efficiency of 20.7%. To transfer the high conversion efficiency to the module, we use the laser welding process named aluminum-based mechanical and electrical laser interconnection for module integration of these back-contacted solar cells. We further analyze the impact of the busbars of our back-junction back-contact cells on the cell performance and report on optimization of the cell/module interface. The new cells have an adapted rear-side geometry by omitting the emitter busbar. A proof-of-concept module consisting of these cells is presented. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the study was to develop a very simple process for the fabrication of large area n-type PERT cells by means of ion implantation. We showed an improvement of the implanted boron activation rate with the annealing temperature by comparing boron SIMS and ECV concentration profiles. A direct positive impact on the boron emitter saturation current density (J0e) was measured. We also investigated the effect of varying the oxidation conditions during the annealing on the implanted boron emitter and the phosphorus BSF quality. Low emitter saturation current density (J0e) of 131 fA/cm2 was measured on textured surfaces, close to the value obtained with diffused B-emitters. A process flow was developed leading to an average efficiency of 19% on 239 cm2 bifacial solar cells, using only eight processing steps with two implantations and one activation annealing. [Copyright &y& Elsevier]

Abstract: First n-type Czochralski silicon (Cz-Si) metal wrap through (MWT) solar cells based on the high-performance MWT (HIP-MWT) concept are presented. Reference n-type H-pattern solar cells were processed in parallel. The MWT as well as the H-pattern cells with an edge length of 125mm are completely metallized by screen printing. The fabricated n-type Cz-Si MWT solar cells achieved conversion efficiencies up to 17.7%. One of the main challenges for further development is to decrease the dark saturation current density j 02 and to increase the shunt resistance R Shunt above the current value of about 1 kΩcm2 The H-pattern reference cells also show similarly low R Shunt as well as high j 02 values and reach conversion efficiencies up to 17.1%. Thus the low R Shunt and high j 02 values cannot be attributed to the MWT concept. Specific contact resistances of about 8 mΩcm2 for front and rear metallization show the successful electrical contacting of the differently doped surfaces using sequential tube furnace diffusions. The advantage of less metallized front surface for the MWT cells compared to the H-pattern references is clearly visible in increased values for short-circuit current density and open-circuit voltage. With the results obtained, the feasibility of the transfer from p- to n-type Cz-Si is demonstrated. [Copyright &y& Elsevier]

Abstract: N-type Si solar cells gradually arrest comprehensively attention due to the potential to achieve high cell efficiency without light-induced degradation compare to p-type cells. Meanwhile, the rapid fall in photovoltaic price drives many researchers to continue developing multifarious technologies about efficiency improvement and cost reduction in the manufacture of solar cell process. In this article we introduce large area bifacial solar cells on n-type silicon using only industrial facilities. The boron emitter is formed by diffusion technique with BCl3 precursor and the phosphorus BSF is made by ion-implantation followed by an in-situ front and back passivation with dry oxidization. The resulting cell efficiency has achieved 19.7% on 156PSQ Cz wafers and zero LID has been proved after 72h exposure at 50°C under AM1.5G illumination. In addition, 3.03% of cell to module loss is confirmed using the structure of 36pcs n-bifacial cells with normal front glass and transparent backsheet. [Copyright &y& Elsevier]