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Tensile Stress-Dependent Fracture Behavior and Its Influences on Photovoltaic Characteristics in Flexible PbS/CdS Thin-Film Solar Cells
journal contribution
posted on 2015-03-04, 00:00 authored by Seung Min Lee, Deuk Ho Yeon, Bhaskar Chandra Mohanty, Yong Soo ChoTensile stress-dependent fracture
behavior of flexible PbS/CdS heterojunction thin-film solar cells
on indium tin oxide-coated polyethylene terephthalate (PET) substrates
is investigated in terms of the variations of fracture parameters
with applied strains and their influences on photovoltaic properties.
The PbS absorber layer that exhibits only mechanical cracks within
the applied strain range from ∼0.67 to 1.33% is prepared by
chemical bath deposition at different temperatures of 50, 70, and
90 °C. The PbS thin films prepared at 50 °C demonstrate
better mechanical resistance against the applied bending strain with
the highest crack initiating bending strain of ∼1.14% and the
lowest saturated crack density of 0.036 μm–1. Photovoltaic properties of the cells depend on the deposition temperature
and the level of applied tensile stress. The values of short-circuit
current density and fill factor are dramatically reduced above a certain
level of applied strain, while open-circuit voltage is nearly maintained.
The dependency of photovoltaic properties on the progress of fractures
is understood as related to the reduced fracture energy and toughness,
which is limitedly controllable by microstructural features of the
absorber layer.