Abstract:
This study focuses on fabricating efficient CdS/CdTe thin-film solar cells with thermally
evaporated cuprous iodide (CuI) as hole-transporting material (HTM) by replacing Cu back contact in
conventional CdS/CdTe solar cells to avoid Cu diffusion. In this study, a simple thermal evaporation
method was used for the CuI deposition. The current-voltage characteristic of devices with CuI
films of thickness 5 nm to 30 nm was examined under illuminations of 100 mW/cm2
(1 sun) with
an Air Mass (AM) of 1.5 filter. A CdS/CdTe solar cell device with thermally evaporated CuI/Au
showed power conversion efficiency (PCE) of 6.92% with JSC, VOC, and FF of 21.98 mA/cm2
, 0.64 V,
and 0.49 under optimized fabrication conditions. Moreover, stability studies show that fabricated
CdS/CdTe thin-film solar cells with CuI hole-transporters have better stability than CdS/CdTe thin film solar cells with Cu/Au back contacts. The significant increase in FF and, hence, PCE, and the
stability of CdS/CdTe solar cells with CuI, reveals that Cu diffusion could be avoided by replacing Cu
with CuI, which provides good band alignment with CdTe, as confirmed by XPS. Such an electronic
band structure alignment allows smooth hole transport from CdTe to CuI, which acts as an electron
reflector. Hence, CuI is a promising alternative stable hole-transporter for CdS/CdTe thin-film solar
cells that increases the PCE and stability
