Effects of lateral resistances in photovoltaic cells and full 2-D parameter extraction for the spatially-resolved models using electroluminescence images

This paper investigates the influences of the lateral resistances in photovoltaic (PV) devices, and proposes a method for extracting local electrical parameters of thin-film PV devices based on a 2-D spatially-resolved model utilising electroluminescence (EL) images and 2-D fittings. PV-oriented nodal analysis (PVONA) is used for studying the electrical properties of the devices and for simulations in iterative 2-D fitting processes. It is shown that the effects of the lateral resistances should not be simply replaced by lumped effective resistances. The proposed new method employs firstly the dark-I-V fitting for the junction parameters; and secondly 2-D fitting of EL images taken under varying bias levels, for the internal and lateral series resistances. The method is verified by a case study and demonstrates excellent agreements with measurement data

Spatially and spectrally resolved electroluminescence measurement system for PV characterisation

A system that combines the advantages of fast global electroluminescence (EL) measure-ments and highly detailed spectral EL meas-urements is presented. A Si camera-based EL system is used to measure the intensity of radi-ative recombination of the PV device spatially resolved over its full area. A monochromator-based system is then used to measure local-ised emission spectra at specific points of interest identified, as such as defects and cracks. The first measurement results of a mc-Si and an a-Si PV device show good agreement with reported behaviour of such devices and high-light the potential to distinguish between differ-ent defect types and reveal performance changes that would be missed using camera-based EL only

Accelerated spatially resolved electrical simulation of photovoltaic devices using photovoltaic-oriented nodal analysis

This paper presents photovoltaic-oriented nodal analysis (PVONA), a general and flexible tool for efficient spatially resolved simulations for photovoltaic (PV) cells and modules. This approach overcomes the major problem of the conventional Simulation Program with Integrated Circuit Emphasis-based approaches for solving circuit network models, which is the limited number of nodes that can be simulated due to memory and computing time requirements. PVONA integrates a specifically designed sparse data structure and a graphics processing unit-based parallel conjugate gradient algorithm into a PV-oriented iterative Newton--Raphson solver. This first avoids the complicated and time-consuming netlist parsing, second saves memory space, and third accelerates the simulation procedure. In the tests, PVONA generated the local current and voltage maps of a model with 316 x 316 nodes with a thin-film PV cell in 15 s, i.e., using only 4.6% of the time required by the latest LTSpice package. The 2-D characterization is used as a case study and the potential application of PVONA toward quantitative analysis of electroluminescence are discussed

Distributed electrical network modelling approach for spatially resolved characterisation of photovoltaic modules

Distributed electrical modelling and simulation plays an important role in investigating local operating points and the overall power generation of photovoltaic (PV) modules. A PV module is a three-dimensional device in which inhomogeneities can cause a non-uniform performance and hence, electrical mismatches which consequently reduce the overall power generation. Distributed modelling and simulation can be used to identify local electrical properties and their impacts on the power output. In this study, a flexible, distributed electrical network modelling approach is presented. The proposed approach introduces a hierarchical architecture built up from the diode model-based sub-cell level to the module level. A PV-oriented nodal analysis solver is developed to enable the spatially resolved quantitative analysis of electrical operating points by given local properties including irradiance, temperature, series resistance, shunt resistance and ideality factor. The approach has been verified by PSpice software. The case studies have shown that this modelling and simulation tool can be used to analyse spatially resolved characterisation results and to predict global and distributed operating points under different conditions

Spatially and spectrally resolved electroluminescence measurement system for photovoltaic characterisation

A system that combines the advantages of fast global electroluminescence (EL) imaging and detailed spectrally resolved EL measurements is presented. A charge-coupled device camera-based EL imaging system is used to measure the intensity of radiative recombination of the photovoltaic (PV) device spatially resolved over its full area. A monochromator-based system is utilised to measure localised emission spectra at given points of interest. Measurements of multi-crystalline and amorphous silicon PV devices demonstrate the potential to investigate radiative defects and reveal performance variations and non-uniformities. This links inhomogeneities much closer to device physics than using camera-based EL only