Feasibility of a Full Chalcopyrite Tandem Solar Cell: A Quantitative Numerical Approach

Abstract

The potential of tandem solar cells combining two chalcopyrite absorbers is evaluated using numerical modeling based on an exhaustive set of experimental parameters, offering a high degree of confidence in the numerical values reported herein. The simple yet reliable approach used here combines a transfer matrix‐based optical model of the wide bandgap CIGSe top subcell used as input for the 1D electrical modeling of a reference narrow bandgap CIGSe bottom cell. Various optical optimizations to the top subcell are investigated, with the aim to increase the bottom subcell current and reduce the efficiency threshold needed at the top subcell for the tandem device to beat the current single junction efficiency record. The results here suggest that significant progress compared with the state of the art can be made using a pure CuGaSe2 absorber combined with an optimized back contact with an ultrathin transition metal oxide interlayer. With a bottom subcell current more than doubled in the optimum top subcell configuration, a challenging yet clear pathway for the future realization of tandem solar cells based on chalcopyrite absorbers is offered.

Physical and chemical aspects at the interface and in the bulk of CuInSe2-based thin-film photovoltaics

“…CIGSe is a good material for both single-junction and tandemtype solar cells: we can control the bandgap energy from 1.0 eV to 1.7 eV by varying the GGI ratio, and a 1.4 eV material which is suitable for single-junction solar cells is available with a GGI of about 60% and a 1.7 eV CuGaSe 2 (CGSe) which is applicable for tandem-type solar cell as a top cell is also available derived from these quaternary materials. 73,74 Although the highest efficiency 6 was obtained using a relatively low Ga composition, the degradation of V OC for high-Ga content CIGSe solar cells is still an open issue, and this problem must be addressed to boost the CIGSe solar cell efficiency further. In this section, one of the limitation mechanisms leading to the difficulty of the growth of high-quality CIGS films with high GGI values is discussed, and a possible solution is suggested.…”

Characterization of the Stability of Indium Tin Oxide and Functional Layers for Semitransparent Back‐Contact Applications on Cu(in,Ga)Se2Solar Cells

“…This gives interest to further research on alternative FLs as those based on MoO 3 nanometric layers, which show interesting optical properties as recently reported from first simulation studies. [37] 2. Results and Discussion The substitution of the standard metallic Mo back contact by semitransparent ITO and ITO/MoSe 2 back contacts was studied at different temperatures of the CIGSe coevaporation process to determine the impact of the temperature on such back contacts.…”

“…This gives interest to further research on alternative FLs as those based on MoO 3 nanometric layers, which show interesting optical properties as recently reported from first simulation studies. [ 37 ]…”

2‐step process for 5.4% CuGaSe2 solar cell using fluorine doped tin oxide transparent back contacts

“…One can note the absence of interference fringes in the curves, which is an indication of rough interfaces and light scattering. The optical modeling of an equivalent material stack has been performed using an in‐lab developed transfer matrix code running on MatLab™, 29 where light scattering effects can be modeled following a methodology similar to Ogilvy 30 . The calculated transmission curves for a material stack, including an ultrathin MoSe 2 interlayer at the FTO/CGSe interface, are presented in Figure 7.…”

“…The electrical simulation of wide bandgap solar cells is performed using SCAPS 3.308, and a set of material parameters were reported elsewhere. 29 The optical modeling is made using a self-developed code functioning in MATLAB™ and simulating the complete optical profile of a material stack of known complex optical indices with the transfer matrix approach. Unlike Tiwari et al 29 where only the specular component of the light was considered, light scattering effects are taken into account using the Beckmann-Spizzichino method.…”