Investigation of Deep-Level Defects Lateral Distribution in Active Layers of Multicrystalline Silicon Solar Cells
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Investigation of Deep-Level Defects Lateral Distribution in Active Layers of Multicrystalline Silicon Solar Cells Vladimir G. Litvinov1, Alexander V. Ermachikhin1, Dmitry S. Kusakin1, Nikolay V. Vishnyakov1, Valery V. Gudzev1, Andrey S. Karabanov 2, Sergey M. Karabanov1 and Sergey P. Vikhrov1 1 Ryazan State Radio Engineering University, 59/1 Gagarin Str., Ryazan, 390005, Russian Federation 2 Helios-Resource Ltd., Saransk, Mordovia, 126/1 Proletarskaya Str., 430001, Russian Federation ABSTRACT The influence of deep level defects lateral distribution in active layers of multicrystalline Sibased standard solar cells is investigated. Multicrystalline p-type Si wafers with 156156 mm dimensions and 200 m thickness were used for SCs preparation. One type of solar cells with conversion efficiency 20.4% was studied using capacitance voltage characteristics method (C-V) and by current deep level transient spectroscopy (I-DLTS). From various places along the diagonal of solar cell’s substrate with 20.4% efficiency nine pieces with an area ~20 mm2 were extracted and studied. I-DLTS spectra of the five pieces from solar cell were measured. The features of deep levels defects concentration lateral distribution along the SC’s surface were studied. INTRODUCTION Multicrystalline silicon (mc-Si) based solar cells (SCs) have such advanced technical and economical properties as acceptable lower production cost and relatively high and comparable efficiency of solar energy conversion into electricity to monocrystalline silicon based SCs. Mc-Si is a naturally defective material due to the structural features. The defects or the deep centers (DCs) form deep energy levels (DLs) in the semiconductor band gap. DLs are the centers of free charge carriers recombination. The efficiency of SCs depends on DLs and their parameters such as spatial and lateral distribution and activation energies. In order to optimize the structure and technology of SCs and to obtain advanced parameters it is important to study DLs and their distribution peculiarities. The correlation between the total concentration of deep traps and the values of the SCs conversion efficiency was found early on the example of three type SCs based on multicrystalline silicon (mc-Si) with different efficiencies 10.1, 16.8 and 20.4% [1]. The main purpose of the work is an investigation of the DL’s energy spectrum of defects and their distribution along the active layers of the SCs to improve the undastanding how DL’s defects lateral distdibution influences on the SC’s efficiency. EXPERIMENT Boron doped p-type mc-Si wafer of 0.5-2 cm resistivity was used to fabricate SC by n-type 1 m thick layer forming by phosphorus gas diffusion in the Helios-Resource Ltd. The growing method is the directional solidification. Oxygen content
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