Development of a Technique for Restoring the Efficiency of Film ITO/CdS/CdTe/Cu/Au SCs After Degradation

A study into the influence of direct polarity on the output parameters of ITO/CdS/CdTe/Cu/Au solar cells (SC) has been conducted. We have experimentally registered the effect of an electric field of direct polarity on the output parameters and light diode characteristics of ITO/CdS/CdTe/Cu/Au SCs, which underwent a degradation of efficiency. When a shaded SE is exposed for not less than 120 minutes to the electric field, induced by an external DC voltage of magnitude (0.5‒0.9) V, whose polarity corresponds to the forward bias of n-p heterojunction, there is an increase in efficiency coefficient. This becomes possible if, during degradation of the instrument structure, such defects did not have time to develop, which, over the specified time of exposure, lead to resettable alternating electric microbreakdowns. It has been established that an increase in efficiency coefficient comes at the expense of the increased density of a photocurrent, decreased sequential and increased shunt resistances of SC. Improvement of diode characteristics occurs due to several physical processes. When a SC is fed a forward bias voltage, an electric field forms inside the diode structure of SC, which amplifies the built-in electric field of the rear р-р+ heterojunction and suppresses the built-in electric field of the frontal n+-p heterojunction. That occurs because the diodes are turned on towards each other. The magnitude of a forward bias voltage must not exceed the height of the potential barrier in a heterojunction. In this case, at the rear р-р+ heterojunction and in its adjoining areas from both sides the processes will be intensified that are associated with the transport of copper atoms, the restructuring of complexes of point defects containing copper, and the phase transformations of Cu1,4Te into Cu2-xTe. In addition, under the influence of the field induced by a forward bias voltage, the CuCd- particles from the depletion area of a CdS layer will start moving towards the absorber. That should reduce the resistance part of ...