Pinhole treatment of a CdTe photovoltaic device by electrochemical polymerization technique

An electrochemical treatment was developed to passivate pinhole defects in photovoltaic devices consisting of the device stack: glass substrate/SnO2:F/CdS/CdTe/Cu/Au (metal/back contact). Samples were carefully examined and only those possessing a high density of pinholes through the CdS and CdTe layers were chosen for this study. The presence of a pinhole defect through these layers would lead to the formation of a wire-like connection through the photovoltaic device (shunt), which would seriously degrade the overall performance of the photovoltaic device, on deposition of the metal back contact. We report a solution to this problem wherein the pinhole defects are selectively filled with a resistive material such as polyaniline, using an electrochemical polymerization of the aniline monomer. After the polymer film deposition, this new layer acts as an insulator plug, and prevents the metallic back contact (Cu–Au) from making electrical contact with the transparent conductive oxide (SnO2:F) layer, thus avoiding shunting of the photovoltaic device. Characterization techniques employed in this study are current–voltage measurements to measure the photovoltaic performance of treated and untreated devices and SEM–EDS microscopy and Grazing Angle X-ray diffraction to study the CdTe surface chemistry.