Effect of dislocations on open circuit voltage in crystalline silicon solar cells

Abstract

The dislocation dependence of open circuit voltage is studied based on Donolato's model for the effect of dislocations on minority carrier effective diffusion length [J. Appl. Phys. 84, 2656 (1998)]. Experimental data measured on thin-film solar cells show a strong decrease of open circuit voltage V-oc with an increase in defect density. The analysis of the recombination currents indicates that V-oc is largely reduced by space charge region recombination. For a quantitative study on the relationship between dislocation density, effective diffusion length, and V-oc the data are fitted with an extended version of Donolato's model. Taking into account the base recombination current as well as the space charge region recombination current, the modeled curves fit very well to the experimental data. However, satisfactory fitting results require that the region of high recombination is set wider than the "effective depletion region width," which is calculated from the electrical field strength in a planar p-n junction. This effect can be explained with the assumption of a geometrical enlargement of the p-n junction due to defects like dislocations

Improved dislocation model of silicon solar cells with the effect of front and back surface recombination velocity

“…The boundary conditions at z = 0 and at x = y = ± a are again given by equations (3), (5), and (6). The boundary condition for hole concentration at the junction is…”

“…Dislocations and other crystal defects in a wafer are known to have adverse effect on the cell performance, and in the case of multicrystalline silicon (mc‐Si), they strongly control the cell efficiency. Most of the studies on the effects of dislocations on the cell performance are carried out experimentally . However, it is fruitful to have accurate model to evaluate the effects of dislocations on various cell parameters such as short circuit current density ( J sc ), open circuit voltage ( V oc ), and fill factor.…”

Study of Dislocations in the Minicrystallized Regions in Multicrystalline Silicon Grown by the Directional Solidification Method

“…Crystalline defects-such as grain boundaries [3] and dislocations [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]-impurities [20,21], and foreign inclusions [22][23][24] in mc-Si wafers degrade the PV performance of mc-Si solar cells. In order to enhance the PV performance of mc-Si solar cells, a lot of effort has been devoted to reducing the number of grain boundaries and the dislocation densities in mc-Si [7,25,26].…”

On the origin and formation of large defect clusters in multicrystalline silicon solar cells

“…The reduction of the diffusion length for an increasing dislocation density was modeled by Donolato [5]. On the basis of Donolato's work, Kieliba et al [6] studied the decrease of the open circuit voltage V oc for increasing dislocation densities. In an earlier work, we showed that this applies also for defect clusters [7].…”