Abstract:
CdS/CdTe thin film solar cells have become matured photovoltaic technology, next to silicon solar
cells technology due to ideal band gap, low manufacturing cost, and scalability of CdTe deposition.
Although CdS/CdTe solar cells with copper based back contact have shown the best efficiencies by
reducing roll-over effect and enhancing the electrical properties of CdTe, it is well known that their
performance reduces with time, mainly due to diffusion of Cu through the CdTe absorber. This study
focuses on finding a suitable alternative back contact namely, spiro/Au, MoO3 / Ag, CuI / Au and
Poly(ethylenedioxythiophene): polystyrene sulphonate(PEDOT:PSS) /Au in which Au and Ag contacts were
deposited through thermal evaporation under high vacuum together with MoO3 as a hole transporter while
spiro, CuI and PEDOT:PSS hole transporters were deposited using spin coating technique. Performance of
the device with PEDOT:PSS/Au exhibited the highest short-circuit current density over 24 mAcm-2 together
with an open circuit voltage of 0.39V and a fill factor of 0.32 which resulted an efficiency of 3.04% at solar
simulator intensity of 100 mW/cm2 among the studied material combinations. However, fill factor of this
device was poor in comparison with device with Cu/Au contact, probably due to poor compatibility
between inorganic and organic interface. These solar cell structures were subjected to stability checking
for a period up to 8 months from their fabrication. Device with Cu/Au lost about 5 % of its initial efficiency
while efficiency of device with PEDOT:PSS/Au remained the same over the period of 8 months.
