Junction configurations and their impacts on Cu(In,Ga)Se2 based solar cells performances

Abstract

Schematic representation and band diagram of two cells configuration at the equilibrium: (a) with SDL layer (conventional structure), (b) with P + layer (new structure). • We made a compared study of CIGS solar cell structure, containing SDL layer, with a new reference cell containing P+ layer. • The optimal thickness of the P+ to optimize the solar cells is 10 nm. • The P+ defect density is the critical parameter for the limitation of the performance for the CIGS solar cells. • A wide band-gap BSF layer at the CIGS/Mo interface combined with a p+ layer provides a high-performance and stable CIGS solar cells. One dimension solar cells simulator package (SCAPS) is used to study the possibility of carrying out thin CIGS solar cells with high and stable efficiency. In the first step, we modified the conventional ZnO:B/i-ZnO/CdS/SDL/CIGS/Mo structure by substituting the SDL layer with the P + layer, having a wide bandgap from 1 to l.12 eV. Then, we simulated the J-V characteristics of this new structure and showed how the electrical parameters are affected. Conversion efficiency of 18.46% is founded by using 1.1 μm of P + layer thickness. Secondly, we analyze the effect of increase thickness and doping density of CIGS, CdS and P + layers on the electric parameters of this new structure. We show that only the short-circuit current density (J SC ) and efficiency are improved, reaching respectively 34.68 mA/cm 2 and 18.85%, with increasing of the acceptors density. Finally, we introduced 10 nm of various electron reflectors at the CIGS/Mo interface in the new structure to reduce the recombination of minority carriers at the back contact. High conversion efficiency of 23.34% and better stability are obtained when wide band-gap BSF is used.