The educational-oriented pack of computer programs to simulate solar cell behavior Aleksy Patryn 1 Stanisław M. Pietruszko 2  Faculty of Electronics, Technical University of Koszalin  Insitute of Opto- Microelectronics, Warsaw University of Technology POLAND

Overview of the presentation: Virtual labs in high school education Conception of the virtual labs pack Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor Block 2 of the pack - typical student’s laboratory exercises – solar cell parameter measurement and analysis Conclusions

Virtual labs in high school education The UNSW Key Centre for Photovoltaic … ( PC1D Version 5: 32-bit Solar Cell Modeling on Personal Computers Donald A. Clugston and Paul A. Basore Photovoltaics Special Research Centre University of New South Wales, Sydney 2052, Australia

Virtual labs in high school education PV-Spice ( ) Simulation of Solar Cell Properties with Electronic Circuit Simulation Software

Virtual labs in high school education TU-Berlin ILSE The Interactive Learning System for Renewable Energy

Conception of the virtual labs pack The educational-oriented pack of software to simulate solar cell behavior has been designed in a form of virtual exercises. The first part of the pack is a group of exercises which give the opportunities of introduction to fundamentals of solar cells and to study a role of technology factors on the solar cell parameters. The second part of the pack has been designed in a form of typical student’s laboratory exercises. The main part of that pack gives opportunities to introduce measurement data (values of current depending voltage values) in the same way as in real experiment and do analysis of its characteristic on a base of the simple model.

Conception of the virtual labs pack Virtual laboratory on Solar Cells Parameters Block 1Block 2 Task: solar cell parameters in a relation to its intrinsic characteristics. Variable parameters:  T, n n0, n p0, N t,, W n, W p, s 0, s i,  E t, A Calculated intrinsic parameters:  F n, F p,  n,  p,L n,L p, ,  n,  p, Evaluated output parameters:  I-V (dark and light), , FF,, P max, V max, I max, I (n) ( ), I (p) ( ), I (spl) ( ) Software: MathCAD, MathConnex, LabWindows/CVI Task: simulation of solar cell parameter measurements in a relation to it output characteristics. Variable parameters: T, S, I ph, I o, R s, G ch Evaluated output parameters:  I-V (light), , FF, P max, V max, I max, I (n) ( ), I (p) ( ), I (spl) ( ) Software: Visual Basic

Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor The first block is an application which allows carrying out the analysis of a silicon solar cell structure and, as a consequence, to evaluate its working characteristics. It has been designed in a form of a virtual generator of the output dependencies describing a solar element on entered data or of a material (structure) parameters. Final calculations of cell parameters within this application are based on a two-layer single-diode model but in initial calculations a few more fundamental models have been taken into account. A number of parameters in both n- and p-layers may be taken into account and may be changed (type and concentration of main doping impurities, concentration and energy level of recombination centers, velocity of surface recombination at both front and interlayer surface). The software uses those parameters to evaluate working dark and light I-V characteristics as well spectral characteristics of solar cell in relation to those parameters.

Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor This block of the virtual laboratory is developed on the basis of two software platforms. As a first stage, the complete model and all its calculations were completely created using the MathCAD software.

Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor Part of variable or calculated parameters : T - temperature, n n0, n p0 - free carriers concentrations, N t,  E t, - deep centers (traps) concentration and depth, W n, W p, - width of n- and p-layers of cell structure,  - p-n junction depth s 0, s i, - surface recombination velocity at external and intrinsic surfaces,  A – illumination of the cell when it is measured, F n, F p,- Fermi levels position in n- and p-layers,  n,  p, L n, L p,  n,  p - minority carriers lifetime, diffusion length and carriers mobility n- and p-layers, , - solar cell efficiency, FF – fillfactor, L d - minority carriers diffusion length in bulk Silicon. Symbols I (n) ( ), I (p) ( ), I (spl) ( ) mean current value separately for electrons, holes and current of e-h pairs in the spatial charge layer.

Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor The samples of screen interface in MathCAD part of the exercise. It is seen parameters been calculated.

Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor The working part of the application, using practically same mathematical formulas and practically the same algorithms of calculations as the MathCad part, was executed in a form of independent application (in a form of so called "project") in LabWidows/CVI. Within this block it is possible to carry out change of wide group of input parameters determining structure and internal properties of solar cell parameters

Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor The samples of screen interface in LabWindow/CVI – control panels

Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor The samples of screen interface in LabWindow/CVI – Panels of the results – dark characteristics

Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor Basing on the input parameters, the student can evaluate a number of internal parameters of a solar cell, for example concentration and mobility of carriers in both active layers, their diffusion length and lifetime, depth of the Fermi level, parameters of a spatial charge layer or barrier voltage. The estimation of this parameters are entered into laboratory exercises in the aim of fastening knowledge of the student in the field of physics of semiconductors related to solar cells. The parameters are being evaluated on the basis of the elementary formulas on theory of semiconductors and give an approximate data. The main restriction of used models is that in all cases the semiconductor is assumed as non-degenerate one. The calculations do not give extremely high accuracy but allows students to get a look into interrelation of the internal parameters with output parameters and to estimate real numerical meanings of those parameters, which are necessary for the analysis of working parameters of a solar cell.

Block 1 of the pack - exercises to study fundamentals of solar cells as well as a role of technology factor The samples of screen interface in LabWindow/CVI –panels of the results – light characteristics

Block 2 of the pack - exercises to solar cell parameter measurement and analysis The second block is more traditional set of virtual exercises. This block implements a task of virtual measurements of parameters of a solar cell. It allows a student to define working external and internal parameters of the solar cell on the basis of entered points of the light I-V characteristic of solar cell. Both output and internal standard parameters of solar cells are being evaluated on basis of the numeric data of the I-V curve inputted manually by a user. This block of exercises has been developed using Visual Basic software and it may be used as an independent application as a compiled application.

Block 2 of the pack - exercises to solar cell parameter measurement and analysis The samples of screen interface – control panels

Block 2 of the pack - exercises to solar cell parameter measurement and analysis The samples of screen interface – HELP Menu

Block 2 of the pack - exercises to solar cell parameter measurement and analysis The samples of screen interface – panels of the results Exercise # 1

The samples of screen interface – panels of the results Exercises # 2 and 3

Conclusions Presented pack of virtual student's laboratory on solar cells parameters analysis allows to simulate a number of task related to its topic. The authors consider the package as a first stage to design the following versions to higher research and didactic level. Presented virtual laboratory in any a case does not carry a role of a measuring center. It is only the educational tool allowing to simplify introducing of the students to the whole complex of aspects related to solar cells and to large number of the factors which influence its action. The whole package of the virtual laboratory is available for student and to university teachers within the University network as the installation software in a form of download files by using the user’s access password. The package has been successfully used at Faculty of Electronics, Technical University of Koszalin, and at Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, both in Poland.

The educational-oriented pack of computer programs to simulate solar cell behavior Authors: Prof. dr hab. Aleksy Patryn Dr inż. Stanisław M. Pietruszko POLAND Thank you for your attention.