title: Cocktails of paste coatings for performance enhancement of CuInGaS(2) thin-film solar cells.
abstract: To fabricate low-cost and printable wide-bandgap CuInxGa1-xS2 (CIGS) thin-film solar cells, a method based on a precursor solution was developed. In particular, under this method, multiple coatings with two pastes with different properties (e.g., viscosity) because of the different binder materials added were applied. Paste A could form a thin, dense layer enabling a high-efficiency solar cell but required several coating and drying cycles for the desired film thickness. On the other hand, paste B could easily form one-micrometer-thick films by means of a one-time spin-coating process but the porous microstructure limited the solar cell performance. Three different configurations of the CIGS films (A + B, B + A, and A + B + A) were realized by multiple coatings with the two pastes to find the optimal stacking configuration for a combination of the advantages of each paste. Solar cell devices using these films showed a notable difference in their photovoltaic characteristics. The bottom dense layer increased the minority carrier diffusion length and enhanced the short-circuit current. The top dense layer could suppress interface recombination but exhibited a low optical absorption, thereby decreasing the photocurrent. As a result, the A + B configuration could be suggested as a desirable simple stacking structure. The solar cell with A + B coating showed a highly improved efficiency (4.66%) compared to the cell with a film prepared by paste B only (2.90%), achieved by simple insertion of a single thin (200 nm), dense layer between the Mo back contact and a thick porous CIGS layer.
authors.affiliation: Clean Energy Research Center, Korea Institute of Science and Technology , 39-1 Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Republic of Korea.
authors.forename: Hee Sang
authors.initials: HS
authors.lastname: An
authors.forename: Yunae
authors.initials: Y
authors.lastname: Cho
authors.forename: Se Jin
authors.initials: SJ
authors.lastname: Park
authors.forename: Hyo Sang
authors.initials: HS
authors.lastname: Jeon
authors.forename: Yun Jeong
authors.initials: YJ
authors.lastname: Hwang
authors.forename: Dong-Wook
authors.initials: DW
authors.lastname: Kim
authors.forename: Byoung Koun
authors.initials: BK
authors.lastname: Min