Recently, Prof. Wu Sixin’s group have published their research article “High Efficiency CIGS Solar Cells by Bulk Defect Passivation through Ag Substituting Strategy” in ACS Applied Materials & Interfaces. (ACS Applied Materials & Interfaces, 2020, 12, 12717-12726. IF: 8.456, JCR-1)

Article link: https://pubs.acs.org/doi/abs/10.1021/acsami.9b21354.

Cu(In,Ga)Se2（CIGS）is a kind of chalcopyrite structured, direct band-gap semiconductor with adjustable band gap (1.1-1.7 eV) and high absorption coefficient. Up to now, the record efficiency of the device has reached 23.35%, indicating CIGS the most promising photovoltaics material. However, the complicated deep defects (such as InCu or GaCu) in the CIGS layer act as deep level recombination center, which cause serious photocarrier recombination, thus reducing its device efficiency.

Figure 1 (a) I-DLTS signal of devices A and C. (b) Arrhenius plots corresponding to the peaks derived from DLTS spectra. (c) J−V curve of the champion device. (d) Integral current calculated according to the EQE curve.

In this work, Prof. Wu Sixin’s group introduced Ag substitution to passivate bulk defects in CIGS absorber via a facile but effective solution method. The results showed that Ag was successfully incorporated in the CIGS lattice. The concentration of InCu defect was reduced from 3.45 × 1014 (cm -3) to 6.72 × 1012 (cm-3). The crystallinity of absorber was also improved, observing as eliminating the small grain layer and forming large grains throughout the CIGS layer cross section. A champion Ag-substituted CIGS device exhibited a remarkable efficiency of 15.82%, which is the highest among non-hydrazine-solution method device. This work provided a promising method to passivate bulk defects and further improve the photoelectric conversion efficiency (PCE) of CIGS solar cells.