Silicon-based solar cells Characteristics and production processes ...

Recommendations

Info

Silicon-based solar cells – characteristics and production processes I sh - leakage current R sh - cell’s parallel resistance A 1 - diode’s quality coefficient (value close to 1) A 2 - diode’s quality coefficient (value close to 2) R - external resistance Parameter I sc is described as the short-circuit current, and V oc is the voltage of the open circuit. The I-V characteristics presented in Fig. 25 include the points which determinant for the cell’s photovoltaic conversion efficiency E ff . The value of P m = I m ∙V m is the maximum actual power possible to be obtained from the cell, but always lower than the ideal maximum power being a product of I sc ∙V oc , which is expressed by the filling factor FF in the relation [17]: I V P FF = I V I V m m m = (23) sc oc sc oc Knowing the above I-V characteristics, one can calculate the basic and most important value for the solar cell, which is the value of its photovoltaic conversion efficiency E ff , often described as the cell efficiency, according to the following formula [17]: E ff IscVoc = FF ⋅100% (24) P A in 0 where: P in - intensity of radiation falling on the cell [W/m 2 ] A 0 - cell’s surface area [m 2 ] This is one of the most important quantities determining the market price of the cells sold as commercial product, whose value is given in Euro (€) or USD ($) per watt of the cell power. The decisive factors for the shape of the I-V characteristics are the quantities R s and R sh , which is presented in Fig. 27, with the following marked values: P m (R s ) – maximum cell power with excessive R s , P m (R sh ) – maximum cell power with deficient R sh . 39
Silicon-based solar cells – characteristics and production processes Fig. 27. Effect of the series R s and parallel R sh resistance on the light characteristics of a solar cell. Dependences calculated with the PC-1D computer software, with the established values of R s and R sh for a 100 cm 2 cell. In both cases, P m (R s ) and P m (R sh ) are much lower than P m , due to the effect of the cell’s series and parallel resistance on the latter’s filling factor and the related efficiency, according to the formula (24). The power quoted by the producers of cells and modules refers to the point P m , determined with the STC measurement, and to distinguish this fact, photovoltaics applies the quantity W p (Watt peak), instead of W. The basic fundamental factor conditioning the value of the power P m , possible to obtain from the cell, under the latter’s external work, is the spectral power and characteristics of the solar radiation falling on the cell. Figure 28 presents the energy spectrum of solar radiation, under the conditions AM1.5. 40
Page 1 and 2: EUROPEAN SOCIAL FUND Kazimierz Drab
Page 3 and 4: Table of contents: Project ........
Page 5 and 6: Silicon-based solar cells - charact
Page 41: Silicon-based solar cells - charact

Silicon-based solar cells Characteristics and production processes ...

Create successful ePaper yourself

Delete template?

Save as template?