Soo-Jeong Park

Electronic effect of Na on Cu(In,Ga)Se2 solar cells

We report the effect of Na on the electronic properties of Cu(In,Ga)Se2 (CIGS) thin-film solar cells with a structure of grid/ITO/i-ZnO/CdS/CIGS/Mo/SiOx/soda-lime glass (SLG). The diffusion of Na from the SLG into the CIGS layer was systematically controlled by varying the thickness of SiOx. As the Na content increased, the hole concentration of CIGS was enhanced, while the band-gap was nearly constant, which led to a lower Fermi level in the CIGS towards its valence-band edge. The Na-induced increment in the built-in potential (Vbi) across the n-(ITO/i-ZnO/CdS)/p-CIGS junction yielded an increment of open-circuit voltage that well agreed with the calculated Vbi.

Photoreflectance characteristics of chemical-bath-deposited-CdS layer in Cu(In,Ga)Se2 thin-film solar cells

The authors have characterized the CdS layer in Cu(In,Ga)Se2 thin-film solar cells using photoreflectance (PR) spectroscopy and investigated its influence on the photovoltaic performance. The CdS layer was fabricated by chemical bath deposition with various concentrations of ammonia (1.0–3.0 M), thiourea (0.025–0.1 M), and Cd-salt (0.0004–0.003 M) as well as various thicknesses (30–90 nm). The PR transition energy in CdS increased from 2.282 to 2.366 eV as the thiourea concentration increased from 1.0 to 3.0 M, whereas it decreased as the thickness of CdS increased. The conversion efficiency depended on neither the ammonia and the Cd-salt concentrations nor the thickness of CdS, whereas it changed from 14.72% to 15.81% as the thiourea concentration decreases from 3.0 to 1.0 M.

ZnS buffer layer prepared by sulfurization of sputtered Zn film for Cu(In, Ga)Se 2 solar cells

We report on a novel method of a fabrication of a ZnS buffer layer for an application of Cu(In, Ga)Se2 (CIGS) solar cells. The ZnS thin film was prepared by a sulfurization of a sputtered Zn film using a sulfur cracker. The structural and optical properties of the ZnS films and the photovoltaic performance of the ZnS-employed CIGS solar cells were investigated. The thin ZnS film played a sufficient role as a buffer layer achieving the power conversion efficiency of 10.5%.

The highly sensitive NO2 gas sensor using ZnO nanorods grown by the sol-gel method

Multiple ZnO nanorod device detecting gas was fabricated by sol-gel growth method and gas response characteristics were measured as a chemical gas sensor. The device is mainly composed of sensing electrode and sensing nano material. To acquire high sensitivity of the device for gas it was heated by a heat chuck up to The sensing part was easily made using the CMOS compatible process, for example, the large area and low temperature nano material growth process, etc. The sensors were successfully demonstrated and showed high sensitive response for gas sensing.