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Al 2 O 3 nanolayers, as currently used in the solar industry, provide excellent passivation over the entire injection level range for p -type Si. A high concentration of negative fixed charges guarantees excellent field effect passivation. However, on n -type Si, those fixed charges create an inversion layer at the surface, which opens an additional near-surface recombination channel. This results in a reduced minority carrier lifetime at low injection levels, which is the operation condition of solar cells. In this work, a passivation layer stack is presented, showing excellent performance within the complete injection level range symmetrically for both p - and n -type Si. This layer stack consists of 20 nm Al 2 O 3 combined with a thin HfO 2 or SiO 2 interface. Electrical measurements show a reduction of the fixed charge density to virtually ‘zero’, when the interface layer is adjusted accordingly. This affects the field effect passivation and leads to a decrease of the near surface recombination in n -type Si. The introduction of five cycles of atomic layer deposited HfO 2 improves the effective carrier lifetime in passivated n -type Si from 6 to 15 ms at an injection level of 5×10 12 cm − 3 . The same passivation stack hardly influences the lifetime in p -type Si. The effective surface recombination velocity reaches values below 1 cm/s for both types of substrate doping. In case of the introduction of a 1 nm thick SiO 2 interface, which also results in ‘zero’ fixed charges, the surface recombination velocity reaches a value of up to 200 cm/s due to enhanced surface recombination. The comparison of both passivation stacks shows that the introduction of an ultrathin HfO 2 interface is the most promising approach to achieve a symmetrical passivation layer for p - and n -type Si.

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.

A depth profiling theory for electronic transport properties (carrier diffusivity and lifetime) in ion-implanted semiconductor wafers using infrared photocarrier radiometry (PCR) is proposed. The ion-implanted inhomogeneous sample was sliced into many virtual sub-layers along the depth direction so that the continuously variable electronic properties across the whole thickness can be considered as uniform in each incremental slice. A recursion relationship among the slices was obtained, and the overall PCR signal was built based on contributions from each slice. Experimental lifetime and electronic diffusivity reconstructions of depth profiles at two ion doses (\(3\times 10^{14 }\,\mathrm{cm}^{-2 }{\text { and }}3\times 10^{15}\,\mathrm{cm}^{-2})\) and several implantation energies (from 0.75 MeV to 2.0 MeV) have been demonstrated.

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.

In this work, deep levels introduced by RTA and by subsequent anneals in n-type silicon were studied by deep level transient spectroscopy and by photoluminescence. After annealing at 650 {degree sign}C, centers related to rod-like defects appeared. Furthermore, signals related to thermal donors were found in a wide temperature range. New thermal donors were found even after annealing at temperatures above 900 {degree sign}C. The appearance of rod-like defects indicates that during cooling after RTA soak interstitials supersaturate. The appearance of rod-like defects is accompanied by a decrease of the thermal donor concentration

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.

Homojen ve tekdüze gözenek çapına sahip nano gözenekli anodik aluminyum oksit kalıplar (AAO) kolay üretim tekniği açısından bir çok uygulama alanında geniş yer bulmuştur. AAO kalıplarının yüzeylerininfarklı fonsiyonel gruplar ile modifiye edilmesi, bu yapıların kararlılıklarını arttırdığı gibi uygulamaalanlarını da genişletmektedir. Bu çalışmada, öncelikle düzenli nano kanallara sahip AAO membranlaranodizasyon tekniği ile hazırlanmıştır. Zira, ticari olarak kullanılan AAO membranlarda, düzenli olmayannano kanal yapılarından dolayı uygulama açısından sorunlarla karşılaşılmaktadır. AAO nanogözenekliyapıların potansiyel uygulamalarının arttırılması için yapılar Plazma Destekli Kimyasal Buhar BiriktirmeYöntemi (PECVD) yardımıyla n‐tipi silikon ile kaplanmıştır. AAO membranların n‐tipi silikon ile kaplanmaaşaması öncesinde anodizasyon işlemine maruz bırakılarak düzenli nano kanallar elde edilmiştir.Ardından, PECVD yöntemi ile AAO membran nano‐gözenek yüzeylerinin ve nano kanalların içduvarlanının yaklaşık 40 nm kalınlığında bir n‐tipi silikon tabakası ile kaplanması sağlanmıştır. Bumembranlar AFM, SEM, EDX ve UV‐Görünür bölge absorpsiyon spektroskopisi ile karakterize edilmiştir.Elde edilen membranların 300‐700 nm arasında absorbsiyona sahip olması, mebranların n‐tipi silikon ilekaplandığını ayrıca teyit etmektedir. Elde edilen şeffaf yapıdaki, n‐tipi silikon kaplı membranlar, baştafotovoltaik uygulamalar olmak üzere farklı amaçlara yönelik nano cihaz yapımında kullanılabilir. Nanoporous anodic aluminum oxide (AAO) with uniform and homogen pore diameters has been foundwide range applications due to easy fabrication processes. Modification of AAO template surface bydifferent functional groups increase the stability of these structures and also their potential utility inmany applications. In this study, firstly the membranes which have regular nano‐channels was preparedby anodization technique. In fact, commercially available AAO membranes with non‐uniform nano‐channel formations poses problems in terms of the applications. In order to improve the potentialapplications of AAO nanoporous structures, the surface of AAO membran was coated with an n‐typesilicon by Plasma‐Enhanced Chemical Vapor Deposition (PECVD) Method. Before coating of AAOmembranes with n‐type silicon, the regular nanochannels was obtained by exploring to n‐typeanodization process. Then, the AAO nanoporous membrane surface and the inner wall were coatedwith n‐type silicon layer by PECVD method with thickness of ca. 40 nm. These membranes werecharacterized by AFM, SEM, EDX and UV‐Visible absorption spectroscopy. The resulting membranesexhibit the absorption between 300‐700 nm which confirms also that of n‐type membrane is coatedwith silicone. The obtained transparent n‐type silicon‐coated membranes can be used in theconstruction of nano‐devices for different purposes, including photovoltaic applications.

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.

Secco etchant was conventionally used for delineation of flow pattern defects (FPDs) in lightly-doped Czochralski (Cz) silicon wafers. However, the FPDs in heavily doped n-type silicon wafers cannot be well delineated by Secco etchant. Herein, an etchant based on CrO3-HF-H2O system, with an optimized volume ratio of V(CrO3): V(HF)=1:1, where the concentration of CrO3 is 0.25 M, has been developed for delineation of FPDs with well-defined morphologies for the heavily As- or P-doped n-type silicon wafers.

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.

Via systematic investigation of the anodization of both patterned and unpatterned specimens, phenomena of pronounced discrepancy with respect to pore size, pore density and pore etch-rate were evidenced. Based on the detailed analysis of scanning electron microscope (SEM) micrographs and current-voltage curves, the competition between physical and chemical elements was found to be crucial to understanding the observations. The results indicate that the size, density and growth-speed of pores may act as an evident function of the initial morphology of the sample surface, despite a nearly fixed width of the space charge region. Electric-field effect as well as current-burst-model (CBM) was employed to interpret the underlying mechanism.

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.

Understanding pore growth in semiconductors in detail needs some in-situ information about the processes occurring in a growing pore. It is shown that dual-mode in-situ FFT impedance spectroscopy can provide useful data for macropore etching in n-type Si under back side illumination. A new illumination mode is used alternating with the conventional current-voltage mode, and data evaluation is based on an advanced model developed for this kind of pore etching. The principles of the technique and the basics of the model are introduced and illustrated by a number of examples, some of which show new kinds of pore growth modes.

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)

We have applied Rosenbrock's optimization algorithm to obtain the optimized efficiency of a solar cell and its structural parameters. To obtain these parameters. we have developed a computer pro-ram for simultaneous optimization and simulation of the solar cell. We have used experimental data on the electrical and optical properties of a-Si(1-x)C(x) layers, put them into the written code and obtained the optimized parameters of this solar cell. The maximum efficiency is 6.32% which is close to one experimental result. (C) 2004 Elsevier B.V. All rights reserved.

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 %.

In this study, we demonstrate a concept for optimizing the alloying process for Al-p+ emitter formation with a commercially available aluminum paste, screen-printing technology and belt-conveyor furnace. A more uniform and conformal Al-p+ emitter is obtained at the sample with slow cooling condition of alloying process. Among the 8µm-thick emitters formed by various alloying profiles, the result shows the condition with moderate cooling rate leads to lower J 0e . For long cooling condition with proper ramping, the J 0e of non-passivated p+ is at 217fA/cm2 which corresponds to an implied Voc at 669mV.

Carrier transport and photodetection in heterojunction photodiodes comprising n-type Si substrates and p-type B-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were investigated. Their transport model was discussed mainly on the basis of electrical measurements. It was revealed that an a-C:H matrix in UNCD/a-C:H would predominantly be responsible for carrier transportation in the photodiodes. The photodiodes exhibited high external quantum efficiencies of 72 and 23% under 254 and 365 nm UV illuminations, respectively. These superior responses might be attributable to the photocarrier generation in UNCD grains accompanied by an efficient carrier transport to the a-C:H matrix.

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.

The crystal orientation dependence of macropore formation in n-type Si using aqueous electrolytes provided important information on pore formation mechanisms. Since macropores can also be obtained in organic electrolytes (especially for p-type Si), the orientation dependence for these electrolytes is of interest and therefore was studied. The observed pore morphologies are often remarkably different from the ones observed in aqueous electrolytes under comparable conditions. The results can be understood in terms of the current burst model, Carstensen et al., Mater. Sci. Eng. B 69/70, 23 (2000).

Iridium-related deep levels in n-type silicon were studied by Deep Level Transient Spectroscopy (DLTS). Two different sets of samples were used which differ in the Ir-doping process. Stable Ir isotopes were introduced in the melt during the floating-zone growth process. Other samples were implanted with radioactive mercury isotopes, which decay via gold and platinum to iridium or osmium. In these samples an identification of Ir-related levels from the known half-life of the isotopes is possible. Two dominant levels at E c - 0.28 eV and E c - ().57 eV are assigned to isolated substitutional Ir. Two other levels at E c - 0.17 eV and E c - 0.45 eV are identified as iridium-hydrogen complexes containing one or two hydrogen atoms, respectively.

Using high-resolution Laplace deep-level transient spectroscopy (DLTS), we have compared the electron emission characteristics of vacancy-related defects in silicon. The samples include material irradiated with high-energy protons, material implanted with a heavy ion and silicon irradiated with 2 MeV electrons. We show that in the proton- and electron-irradiated material the DLTS peak in the region of the (- -/-) state of the divacancy at Ec=0.23 eV contains only one feature. The DLTS peak at 250 K which contains the signal derived from the (-/0) state of the divacancy is much larger in ion-implanted silicon than in electron-irradiated silicon. The Laplace DLTS is able to resolve clearly the (-/0) divacancy state and the V–P defect, whereas conventional DLTS shows only a broad peak in that region.