| 초록 |
Among the many types of photovoltaics, CuInxGa1-x(Se,S)2 (CIGSSe) thin film solar cells have been highlighted as an alternative of crystalline silicon solar cells due to many beneficial properties, such as favorable optical properties (e.g. direct energy band gap and high absorption coefficient) and stable structure, to fabricate durable solar cells. Particularly, CIGSSe also has a very attractive property in that the band-gap of the material can easily be tuned by controlling the composition. This enables for graded band gap in the film, which can enhance the solar cell performance by reducing recombination and improving photocurrent due to field assisted carrier collection. In this study, CIGSSe thin films with non-uniform composition were synthesized by a simple paste coating method and subsequent heat treatment under air and a sulfur/selenium atmosphere. The uneven compositional distribution was confirmed to lead to a bandgap gradient in the film. Graded CIGSSe solar cells were demonstrated power conversion efficiency of 11.7% with Jsc of 28.3 mA/cm2, Voc of 601 mV, and FF of 68.6% and the relation between electrical loss and optical loss were characterized. |
