Laura Lancellotti

ENEA | ENEA · TERIN-FSN-DIN

Perovskite solar cells (PSCs) have the potential for widespread application, but challenges remain for a reliable characterization of their performance. Standardized protocols for measuring and reporting are still debated. Focusing on the short circuit current density (JSC), current‐voltage characteristics (J‐V) and external quantum efficiency (EQE...

Graphene is emerging as a promising material for the integration in the most common Si platform, capable to convey some of its unique properties to fabricate novel photonic and optoelectronic devices. For many real functions and devices however, graphene absorption is too low and must be enhanced. Among strategies, the use of an optical resonant ca...

Improving morphological and electronic properties of the electron transport layer (ETL) is a critical issue to fabricate highly efficient perovskite solar cells. Tin dioxide is used as an ETL for its peculiarities such as low-temperature solution-process and high electron mobility and several handlings have been tested to increase its performances....

Perovskite/silicon tandem solar cells have strong potential for high efficiency and low cost photovoltaics. In monolithic (two-terminal) configurations, one key element is the interconnection region of the two subcells, which should be designed for optimal light management and prevention of parasitic p/n junctions. We investigated monolithic perovs...

In this paper a technique based on the analysis of forward bias capacitance for interface characterization in Schottky structure is proposed. In particular, the occurrence of multiple peaks in the capacitance-voltage curve was related to non-uniform properties of the interfaces, for instance undesired localized interface defects. A graphene/silicon...

Electric field enhancement at the center of a Fabry-Perot cavity was exploited for enhancing the absorption of single layer graphene. Large area single layer graphene grown by chemical vapor deposition was embedded in different optical resonant Fabry-Perot cavities with central wavelengths in the Vis, NIR and IR spectral ranges. Fabry-Perot filters...

There is a growing interest toward graphene and 2D materials for their exceptional geometrical, optical, and electronic features, which make them unique for photonic and optoelectronic applications. Achieving extraordinarily high absorption by the electric field enhancement on a single atomic plane is a challenging goal for physics and for many of...

In this paper graphene on silicon solar cells, adopting either gold contacts or graphite contacts, are characterized by means of the impedance spectroscopy analysis. Experiments are described in terms of equivalent circuit model, and lumped parameters allowing to reproduce experiments in the whole set of frequency and dc biases are given. From this...

Substoichiometric molybdenum oxide (MoOx) has good potential as a hole-collecting layer in solar cells. In this paper, we report on the application of ultrathin evaporated MoOx as a hole collector at the back side of two distinct photovoltaic technologies: polymeric and silicon heterojunction (SHJ). In the case of polymer solar cells, we test MoOx...

Chemical Vapor Deposited (CVD) graphene is an attractive candidate as transparent conductive electrode (TCE) for solar cells. Here it is proposed as TCE for silicon heterojunction solar cells (Si-HJSCs) and tested over devices with area up to 4 cm² realized on n-type c-Si wafers with three different p-type emitters facing the dry-transferred graphe...

In this work, front contacts for graphene-based solar cells are made by means of colloidal graphite instead of gold. The performance is characterized by exploiting impedance spectroscopy and is compared to the standard gold contact technology. Impedance data are analysed through equivalent circuit representation in terms of lumped parameters, suita...

We have applied p-type nanocrystalline silicon-oxide (p-SiOx) as front emitter in silicon heterojunction solar cells. The evolution of structural, optical, and electrical properties of p-SiOx as a function of the carbon-dioxide/silane flow rate ratio used in the gas mixture has been investigated, comparing also the film characteristics with those o...

Graphene has recently emerged as a promising candidate for a wide range of photonic and optoelectronic applications, with a high application potential in devices using infrared radiation. The optical absorption of 2D materials and graphene can be uniquely enhanced when they are embedded in optical resonant cavities, since optically-thin atomic-thic...

In Schottky barrier solar cell (SBSC), the interface between absorber and front electrode plays a vital role for reducing the dark current, blocking the majority carriers injected into the electrode at forward bias, reducing surface recombination and passivating the silicon surface. In this respect, the addition of interfacial layer between the sem...

We investigated the possible application of molybdenum oxide (MoOx) on the backside of p-type SHJ solar cells as substitute for the silicon-based back surface field layer. Solar cells with 4 cm² area were fabricated on FZ c-Si(p) <100> wafers, passivated with ultrathin i-a-Si:H buffers. A nanocrystalline n-SiOx emitter was applied while on the back...

In the present work we have tested the effects of two of the most used graphene chemical dopants, nitric acid (HNO3) and thionyl chloride (SOCl2), on multilayer graphene/n-silicon (G/n-Si) Schottky barrier solar cell completed with a double antireflection coating (DARC). The DARC has been realized with a MgF2/ZnS thermal deposition on graphene. In...

We present and discuss advances in the development of p-type Si heterojunction solar cells with Al-doped ZnO (AZO) on both front and rear side, by means of mixed-phase Si- and SiOx-based doped layers. We demonstrate that while rear AZO can be deleterious when using p-type amorphous silicon (a-Si:H), p-type microcrystalline silicon (μc-Si:H) allows...

In this work a silicon based hybrid junction solar cell with transparent conductive oxide (TCO) as top contact and including a layer composed by 3-aminopropyltriethoxysilan (APTES) and soluble graphene oxide (GO) with the structure of TCO/AGO/Si (where the layer formed by APTES and GO is referred to as AGO) was fabricated and tested. The realized s...

We have compared different Ag-based back reflectors (BRs) applied to superstrate-type microcrystalline Si devices grown on Asahi U glass. In particular, substitution of the conventional ZnO:Al layer by MgF2, with lower refractive index and no free-carrier absorption, has been investigated. As electrical issues can mask the optical performance of th...

Silicon heterojunction solar cells have largely demonstrated their suitability to reach high efficiencies. We have here focused on p-type c-Si wafers as absorber, considering that they share more than 90% of the solar cell market. To overcome some of the issues encountered in the conventional (n)a-Si:H/(p)c-Si configuration, we have implemented a m...

Organometal halide perovskites are promising candidates as high bandgap absorbers in multijunction solar cells for targeting cost reductions by ultrahigh conversion efficiencies. For monolithic integration with existing silicon based bottom cells planar architectures are more convenient. Additionally, the planar configuration potentially provides e...

CH 3 NH 3 PbI 3 layers have been prepared by two-step procedure (spin coating and dipping) on flat substrates under open-air conditions and high relative humidity. The films have been characterized by means of scanning electron microscopy, absorption coefficient and x-ray diffraction when varying spinning rate, washing procedure and dipping time. I...

The interfacial layer in a Schottky barrier solar cell (SBSC) plays an important role in reducing the dark current, blocking the majority carriers injected into the frontal electrode at forward bias, reducing surface recombination velocity and passivating silicon surface. All these effects reflect into an improvement of the device performance. Inte...

The transfer of chemical vapor deposited graphene is a crucial process, which can affect the quality of the transferred films and compromise their application in devices. Finding a robust and intrinsically clean material capable of easing the transfer of graphene without interfering with its properties remains a challenge. We here propose the use o...

Schottky barrier solar cells based on graphene/n-silicon heterojunction have been fabricated and characterized and the effect of graphene molecular doping by HNO3 on the solar cells performances have been analyzed. Different doping conditions and thermal annealing processes have been tested to asses and optimize the stability of the devices. The PC...

Surface texturing plays an important role to reduce light reflection and improve light confinement within silicon substrate thus resulting in solar cell efficiency enhancement. In this paper wet anisotropic texturing and subsequent wet isotropic smoothing of different thickness c-Si wafers are investigated to light trapping improvement. The influen...

We report a theoretical study about the performances of graphene on semiconductor Schottky barrier solar cells with the aim to show the potentiality of this kind of device. The simulations are carried by a generalized equivalent circuit model, where the circuital parameters are strictly dependent on the physical properties of the graphene and semic...

The overall conductance of a metal-oxide-semiconductor structure, biased in the inversion regime, is described as the superposition of terms depending either on the minority carrier conductance GN or on the interface state dissipative contribution R _it. Derived analytical expressions are suitable for closed-form solutions allowing the ex...

The aim of this work is to present a procedure for assessing the degradation of Concentration Photovoltaic (CPV) modules, equipped with silicon solar cells operating outdoors in real-time conditions, by measuring various PV module performance parameters before the cells are deployed outdoors and periodically afterwards. To understand the origin of...

Commercial concentrator systems yield to non-uniform illumination profiles. This is a source of degradation for the performances of solar cells and further worsen by the consequent non-uniform temperature distribution. The modelling of these effects can be effectively performed only if three-dimensional effects due to the lateral flow of the curren...

Sunlight concentration onto photovoltaic cells can contribute to reduce the total system cost of photovoltaic plants. The aim of this work is the development of a low cost photovoltaic concentration system design for building integration; to reduce the cost of these systems, you can use concentration PV cells coming from conventional systems and mo...

There are several factors that can affect the reliability of concentration solar cells and influence the final devices performances. Electrical characterizations like the dark I-V curve in reverse and forward bias, the I-V curve under illumination and the quantum efficiency are generally used to test the stability of the cells. For this reason also...

We report on the effect of the annealing temperature (range 600–1100 °C) on amorphous silicon-rich nitride films deposited by PECVD at 300 °C. The evolution of Raman spectra, room temperature photoluminescence, and optical absorption has been investigated on samples with different stoichiometry. Evidence of partial phase separation, with silicon-ri...

This paper deals with the modeling of series resistance components in silicon concentrator solar cells. The main components of the macroscopic series resistance are analyzed by means of one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) numerical simulations. It is shown that the contribution of the lateral current flux, flowing...

The heterojunction crystalline silicon (c-Si) solar cell is one of the most promising cell structures for highperformance and low-cost solar electricity generation. Simple devices based on ZnO/a-Si:H/c-Si/metal heterostructures had been realized by low temperature PECVD (Plasma Enhanced Chemical Vapor Deposition) of amorphous silicon thin film on p...

The necessity of cost-reduction for solar generated electricity has evidenced photovoltaic concentrators as promising technology for the PV industry. One of the most fundamental steps in the fabrication process of high efficiency c-Si solar cells designed for concentrating systems is the realization of a good passivation oxide on the silicon surfac...

In this work we present a numerical model for the three main components of the series resistance of a concentrator solar cell, related to the base region, the emitter region and the metal grid respectively. The model clearly highlights the relative weight of each of them and justifies the drop of efficiency experimentally seen at high concentration...

Due to the improving costs of silicon ingots, light concentration is coming back as promising technology for the PV industry. Optical concentrators focus direct sunlight in order to increase the intensity of the radiation thus allowing the shrinking of the PV receiver whose area can be reduced accordingly to the concentration factor. Small cells ge...

The concentration of sunlight on photovoltaic cells and, consequently, the substitution of expensive photovoltaic areas with less expensive optical concentrators can contribute to reduce the total system cost of photovoltaic plants; unfortunately, this approach involves some new problems regarding the handling of heat, the reduced dimensions of ele...

In this work reverse recovery measurements are used to determine the recombination lifetime in finished silicon solar cell. Usual drawbacks of the classical technique are overcome thanks to an integral analysis of the recovery curve. Experiments on silicon cells with high and low base resistivity and subjected to different thermal treatments for th...

A new analytical model is used to describe the emitter of silicon solar cells in order to gain information on the surface recombination velocity S. The procedure takes advantage of the combined use of experimental measurements, done to determine the emitter saturation current Joe, and analytical modelling to relate Joe to S. Several experiments hav...

In the present work we have investigated the influence of the emitter doping on the cell performance of c-Si devices at one sun and under concentrated light. We have realized diffe- rent devices using FZ p-type Boron doped wafers and varying the sheet resistance of the emit- ters aiming at analyzing the effects of junction depth and concentration o...

Recent important works made at UNSW have demonstrated record efficiency electroluminescence (EL) and photoluminescence (PL) achieved with Si-LEDs realized from high-efficiency PERL silicon solar cells. These outstanding results are due to the relevant technological improvements reached on both light trapping and surface passivation and disclose new...

The light backscattered by different types of textured crystalline silicon samples was investigated with the aim to find a correlation between light collection and light backscattering properties. Different families of texture geometry were considered: inverted pyramids, hemispherical wells, and porous silicon. For each texture family, different sa...

The angular distribution of infrared radiation emitted by Si-LEDs, realized by direct driving high efficiency single-crystalline silicon solar cells, has been analyzed at different wavelengths in the 1000–1200 nm range and at room temperature. Measurements were carried out at far-field conditions on devices realized with different dimensions and di...

Light backscattering properties of a variety of textured crystalline silicon samples were analyzed by measuring the aspect ratio of light intensity angular distribution. Unpolarized laser beams at 543 and 633 nm, incident orthogonally to the silicon surface, were used in the experiments. Different types of texturisation were analyzed: inverted pyra...

The response of two different types of nanostructured gas sensor to oxygen has been investigated. The first (optical) is based on the photoluminescence quenching effect of a porous silicon sample, the second on the changes of the electrical conductance v. environment of a porous silicon free standing membrane on an insulating neutral substrate. The...

Thin luminescent silicon layers are fabricated and placed on various substrates using a purely wet-chemical process at room temperature. To this aim, silicon powder with an average grain size of about 0.1 mum is etched in a HF:HNO3 solution. During the reaction, a coalescence phenomenon is observed resulting in the formation of the photoluminescent...

Porous silicon (PS) layers with 60% porosity and 80 mu m thick were prepared from n-type silicon wafer. We present the sensitivity of PS photoluminescence to 250 ppm of carbon monoxide. Besides the variation of conductivity of the device due to presence of organic vapors such as chloroform, methanol, ethanol and toluene have been carried out.

Macroscopic stress measurements are used to monitor Porous Silicon processing. Silicon wafer of 1 Omega cm resistivity, n-type and < 1 0 0 > orientation were used as starting material. Porous Silicon layers with a porosity of 57% and a thickness of 85 mu m, fabricated by electrochemical anodisation, were differently dried, then the evolution of the...

The photoluminescence response of a series of porous silicon samples, obtained by electrochemical etching of n-type CZ-silicon, has been recorded in various gas environments. A quenching is reported when porous silicon is in the presence of an oxidising ambient (dry air or acetone vapours in dry air). Process reversibility depends on the duration o...