Design of Cascaded Heterostructured p-i-i-n CdS/CdSe Low Cost Solar Cell

Dominant presence of silicon in solar cells manufacturing is defined by maturity of its technology, and low cost of thin film solar cells made from this material. Better efficiency of cascaded solar cells compared to tandem devices performance was demonstrated in our previous work. It was previously demonstrated that some II-VI compounds are less costly than silicon and very efficient when used in solar cells. We present a novel p-i-i-n cell made of wide-gap, Eg=2.42eV, CdS and smaller energy gap, Eg=1.74eV, CdSe. The solar cell consists of top 0.1μm thick acceptor-doped (2*10
¹⁸
cm
^-3
) CdS layer followed by 2μm of intrinsic CdS; next, CdSe intrinsic region of 2μm, followed by 1μm of donor-doped (10
¹⁶
cm
^-3
) CdSe bottom layer. The energy diagram of cascaded solar cell illustrates favorable conditions for collection of both photo-electrons and photo-holes. Presence of wide-energy-gap CdS at the top of the device minimizes significantly the heat-up effect of following layers of CdSe. Solar cell demonstrated following performance characteristics: open-circuit voltage, Voc=1.45V; short-circuit current density, J
_sc
=23.36 mA/cm
²
; filling factor, FF=75%; efficiency equal 18.38%. The parameters listed are presenting operational of a very small segment of a solar cell. The surface area of the segment is 1μm
²
. Our future study will be focused on design and production of CdS/CdSe solar cell deposited on thin CuO film.