| AVS 62nd International Symposium & Exhibition | |
| Energy Frontiers Focus Topic | Monday Sessions |
| Session EN+AS+EM+NS+SE+SS+TF-MoM |
| Session: | Solar Cells I |
| Presenter: | Sung Heo, Samsung Advanced Institute of Technology, Republic of Korea |
| Authors: | S. Heo, Samsung Advanced Institute of Technology, Republic of Korea H.I. Lee, Samsung Advanced Institute of Technology, Republic of Korea J.B. Park, Samsung Advanced Institute of Technology, Republic of Korea G.S. Park, Samsung Advanced Institute of Technology, Republic of Korea D.H. Lee, Samsung, Republic of Korea J.G. Nam, Samsung, Republic of Korea H.J. Kang, Chungbuk National University, Republic of Korea B.D. Choi, Sungkyunkwan University, Republic of Korea |
| Correspondent: | Click to Email |
Cu(In,Ga)Se2 (CIGS)-based solar cells was investigated with an aim of enhancing cell performance because these cells provided high conversion efficiency at relatively low cost. The efficiency of CIGS cells has recently approached 19.7% at small sizes. In general, Cu(In1-x,Gax)(Se1-ySy)2(CIGSS) composition profiles are double-graded, and they can improve the open-circuit voltage (VOC) and the efficiency of solar cells because band gaps increase toward both the surface (i.e., with the increase of sulfur) and the bottom (i.e., with the increase of gallium). It is important to accurately measure the band gap at the top and the bottom of the CIGSS cell. Nevertheless, the band gap profile measurement of the CIGSS as a function of depth is challenging.
In this study, we obtained the depth profile of the CIGSS cell using the quantitative Auger Electron Spectroscopy method, for which the relative sensitivity factor was corrected using the inductively coupled plasma-atomic emission spectrometry (ICP-AES) method. We also measured the band gap directly using high-resolution reflection electron energy loss spectroscopy (HR-REELS) with a monochromatic electron gun, which has low electron energy at 300 eV.
For the direct measurement of a band gap profile, HR-REELS spectra were obtained as a function of depth during Ar ion sputtering at 3.0 kV. The band gap profile shows a double-graded band gap as a function of depth. The band gap values are 1.32 eV at the surface (Eg1), 1.08 eV at the depth between 0.3 and 0.7μm (Eg min.position), and 1.50 eV at the depth of about 2.2 μm (Eg2), respectively. Our findings suggest a new analytical method which directly determines the band gap profile as function of depth.