Abstracts Book - IMRC 2018

• SC4-P116
ELECTRO-OPTICAL CHARACTERIZATION AND MODELING OF
NANOWIRE CdS-CdTe SOLAR CELLS
Riasad Badhan 1 , Hongmei Dang 1 , Rasika Ganvir 1 , Deepak Kumar 1 , Matthew Dye 1 , Vijay Singh 1
1 University of Kentucky, Electrical and Computer Engineering, United States.
Optoelectronic characteristics of Nanowire (NW) CdS-CdTe solar cells were
measured and analyzed. Current vs. Voltage (I-V) measurements revealed that
tunneling followed by the interface recombination was the dominant current
flow mechanism both under light and in the dark. A theoretical model was
developed in order to explain the significant features in the experimental results
obtained I-V and C-V measurements for the nanowire CdS-CdTe solar cells over
a wide (40-300 o K) range of device temperatures. Furthermore, numerical
simulations of I-V characteristics of nanowire CdS/CdTe solar cells were
performed as a function of temperature using SCAPS-1D. Experimental currentvoltage
(I-V) characteristics were compared with the numerical (I-V) simulations
obtained SCAPS-1D at various temperatures in order to identify and evaluate
the parameters responsible for improving the efficiency of these solar
cells. Simulated model explained the important effects of these solar cell
devices, such as the crossover and the rollover effects in the I-V characteristics.
A correlation was found to exist between the crossover effect and a defect in the
i-SnO2 buffer layer. Simulations were also performed to validate the back to back
diode model in order to explain the rollover effect. At the back electrode, the
majority carrier barrier height was numerically varied 0.4 to 0.5 eV; the curve
corresponding to the 0.5 eV barrier showed a strong rollover effect, while this
effect disappeared when the barrier was reduced to 0.4 eV. Clearly the barrier
height at the back contact is a critical parameter in the performance of this solar
cell. The effects of various parameters, including interface state density, CdS and
CdTe carrier concentrations, mid gap trap levels and their concentrations,
contact metal work function, on the dark and light I-V characteristics curves were
studied and the optimum values for these parameters were obtained in order
to get the highest power conversion efficiency with no crossover or rollover
effect. Using practically attainable parameter values, the highest efficiency for
nanowire CdS-CdTe devices was found to be 24% with a Jsc value of 26.724
mA/cm 2 and Voc of 983 mV at 300 K.
Keywords: Nanowire CdS-CdTe solar cells, Tunneling current, SCAPS-1D
Presenting authors email: vsingh@uky.edu