Electronically active layers and interfaces in polycrystalline devices: Cross-section mapping of CdS/CdTe solar cells

Abstract

Electronic mapping of cross sections of a polycrystalline device, the n-CdS/p-CdTe solar cell, show that the photovoltaic and metallurgical junctions coincide to within experimental resolution (50 nm), which rules out both type conversion of CdS and buried homojunctions. Compositional analysis of the CdS supports this. Mapping was done using scanning capacitance, complemented by scanning Kelvin probe microscopy. Our results explain why a high-resistance transparent conducting oxide layer is needed as contact to the CdS for successful device operation. They define limits on inputs for modeling performance of these devices.

From atomic structure to photovoltaic properties in CdTe solar cells

“…There is also an obvious increased collected current, indicating an increased charge carrier separation and efficiency, at those regions. The higher efficiency of the GBs suggests that an internal electric field exists between the GB core and the bulk material, as has been proposed previously [70][71][72][73]. Other EBIC results have shown that the increased current collection at the grain and ∑ 3 boundaries is affected by the CdCl 2 heat treatment and Cu diffusion from the contact layer, and that the CdCl 2 heat treatment increases the carrier collection much more significantly than the Cu diffusion.…”

Impact of Monovalent Cation Halide Additives on the Structural and Optoelectronic Properties of CH3NH3PbI3 Perovskite

“…KPFM is a powerful technique based on measuring and compensating the electrostatic forces between a sample and an AFM tip to determine the local contact potential difference (CPD) [35,36] , which is a measure of the Fermi level energy if the electron affinity is known. Previously, it has been used to study the electrical potential distribution across the internal interfaces of inorganic solar cells [37,38] . KPFM was recently used to characterize the perovskite top layer [39,40] , where the presence of a small potential barrier at the grain boundaries was found.…”

Studies of Basic Electronic Properties of CdTe-Based Solar Cells and Their Evolution During Processing and Stress: Final Technical Report, 16 October 2001 - 31 August 2005

“…Though we have shown direct evidence of the non-uniformity mitigating properties of the HRT, the exact mechanism has not been discussed. Visoly-Fisher et al propose that the HRT serves to add additional thickness to the n-type layer that is necessary for high V oc [35]. Accordingly, the full benefits of the HRT are realized when the CdS is intentionally thinned to increase photocurrent (a variation not performed here).…”