Rodrigo Martins

The behaviour of a microcrystalline p-i-n junction locally illuminated with monochromatic radiation (incident power of 50 mW/cm2) is analysed by means of numerical experiences. The model used for the two-dimensional analysis of the transport properties of a μc-Si:H p-i-n photo-detector is based on the simultaneous solution of the continuity equations for holes and electrons together with the Poisson's equation. The solution is found on a rectangular domain, taking into account the dimension perpendicular to the junction plane and one on the parallel plane. The lateral effects occurring within the structure, due to the non-uniformity of the illumination, are outlined. The results we present show that the potential profile has a linear variation from the illuminated to the dark neutral region. The lateral components of the electric field and of the current density vectors reveal to be mainly localised inside the doped layers.

Microcrystalline silicon is a two-phase material. Its composition can be interpreted as grains of crystalline silicon imbedded in an amorphous silicon tissue, with a high concentration of danglind bonds in the transition regions. In this paper, results obtained by means of numerical simulations about the transport properties of a μc-Si:H p-i-n junction are reported. The role played by the boundary regions between the crystalline grains and the amorphous matrix is taken in account, and these regions are treated similarly to a heterojunction interface. The influence of the local electric field at the grains boundary transition regions on the internal electric configuration of the device is outlined under illumination and applied external bias. © 1999 Elsevier Science S.A. All rights reserved.

We present here a two-dimensional numerical simulation of a hydrogenated amorphous silicon p-i-n solar cell non-uniformly illuminated through the p-layer. This simulation is used to show the effect of the presence of dark regions in the illuminated surface on the electrical behaviour of the device. The continuity equations for holes and electrons together with Poisson's equation, implemented with a recombination mechanism reflecting the amorphous structure of the material, are solved using standard numerical techniques over a rectangular domain. The results obtained reveal the appearance of a lateral component of the electric field and current density vectors inside the structure. The effect of such components is a lateral carrier flow of electrons inside the intrinsic layer and of holes inside the p-layer, resulting in leakage of the transverse current collected at the contacts and an increase in the series resistance.

This paper is concerned with the modelling and simulation of amorphous and microcrystalline silicon optoelectronic devices. The physical model and its mathematical formulation are extensively described. Its numerical reduction is also discussed together with the presentation of a computer program dedicated to the simulation of the electrical behaviour of such devices. This computer program, called ASCA (Amorphous Silicon Solar Cells Analysis), is capable of simulating, on one- and two-dimensional domains, the internal electrical behaviour of multi-layer structures, homojunctions and heterojunctions under simple or complex spectra illumination and externally applied biases. The applications of the simulator presented in this work are the analysis of μc/a-Si:H p-i-n photovoltaic cell in thermal equilibrium and illuminated by monochromatic light and the AMI.5 solar spectrum, with and without polarisation. We also study the appearance within the device of lateral components of the electric field and current density vectors when the illumination is not uniform. © 1999 IMACS/Elsevier Science B.V. All rights reserved.

We report here about a computer simulation program, based on a comprehensive physical and numerical model of an a/μc-Si:H p-i-n device, applied to the 2D problem of describing the transport properties within the structure under non- uniform illumination. The continuity equations for holes and electrons together with Poisson's equation are solved simultaneously along the two directions parallel and perpendicular to the junction. The basic semiconductor equations are implemented with a recombination mechanism reflecting the microcrystalline structure of the different layers. The lateral effects occurring within the structure, due to the non-uniformity of the radiation are outlined. The simulation results obtained for different wavelengths of the incident light are compared and shown their dependence on the energy of the radiation. The results of simulating a p-i-n μc-Si:H junctions under non-uniform illumination is that the generated lateral effects depend not only in intensity but also in direction on the wavelength of the incident radiation. ©2004 Copyright SPIE - The International Society for Optical Engineering.

The introduction into a traditional p.i.n structure of two defective buffer layers near the p/i and i/n interfaces can improve the device stability and efficiency through an enhancement of the electric field profile at the interfaces and a reduction of the available recombination bulk centers. The defectous layer ("i′-layer"), grown at a higher power density, present a high density of defects and acts as "gettering centers" able to tailor light induced defects under degradation conditions. If the i-layer density of states remains below 1016 eV-1 cm-3 and assuming a Gaussian distribution of defect states, the gettering center distribution will not affect significantly the carrier population but only its spatial distribution. We report here about a device numerical simulation that allows us to analyse the influence of the "i′-layer" position, thickness and density of states on the a-Si: H solar cells performances. Results of some systematic simulation from the ASCA program (Amorphous Solar Cell Analysis), and for different configurations will be presented. © 1994 Materials Research Society.

The introduction into a traditional p.i.n. structure of two defective buffer layers near the p/i and i/n interfaces can improve the device stability and efficiency through an enhancement of the electric field profile at the interfaces and a reduction of the available recombination bulk centers. The defectous layer (`i-layer'), grown at a higher power density, present a high density of the defects and acts as `gettering centers' able to tailor light induced defects under degradation conditions. If the i-layer density of states remains below 1016 eV-1 cm-3 and assuming a Gaussian distribution of defect states, the gettering center distribution will not affect significantly the carrier population but only its spatial distribution. We report here about a device numerical simulation that allows us to analyze the influence of the `i- layer' position, thickness and density of states on the a-Si:H solar cells performances. Results of some systematic simulation rom the ASCA program (Amorphous Solar Cell Analysis), and for different configurations will be presented.