Formation and analysis of graded CuIn(Se1−ySy)2 films

Post-Deposition Sulfur Incorporation into CuInSe2 Thin Films

“…Engelmann, et al [6] described the S incorporation into CuInSe 2 films as a 2-step process. The first step is the chalcogen exchange reaction at the solid-gas interface, and the second step is the diffusion of S into the film and of Se out of the film.…”

“…In addition, films with small grains take up S faster than films with large grains [4,5]. In Cu-rich CuInSe 2 films on SL substrates, S incorporation has been quantitatively described as a combination of bulk and grain boundary diffusion [6]. On CuGaSe 2 and Cu(In,Ga)Se 2 films, post-deposition sulfurization produces a completely sulfurized surface layer that has been correlated with a structure visible in scanning electron microscope (SEM) cross-sectional images [7].…”

Synthesis of homogeneous pentenary chalcopyrite alloys with a classical two-step growth process

“…The efficient incorporation of S into these films is also problematic and postannealing of graded Cu(In 1Kx Ga x )Se 2 films in a H 2 S/Ar atmosphere resulted in the formation of a thin Cu(In,Ga)(Se,S) 2 layer on the surface of the absorber layer [1,3]. A significant amount of research has been conducted to understand the driving force behind the phase separation as well as optimization of the Ga and S distribution in absorber layers prepared by two-step processes [4][5][6].…”

A High‐Efficiency Solution‐Deposited Thin‐Film Photovoltaic Device

“…Despite offering many potential advantages, CIGS is a relatively complex material, consisting of at least four elements, with the device performance being significantly impacted by the detailed compositional profile in the absorber layer. [6][7][8][9] Additionally, because grain boundaries act as recombination centers for electrons and holes created during photon absorption, deposited films must exhibit well-formed preferably micrometer-scaled grains of carefully controlled stoichiometry to achieve acceptable device performance. Currently, these processing issues are primarily addressed for high-efficiency devices by using multistep vacuum-based techniques (e.g., evaporation or sputtering).…”

“…Typically, a graded Ga/(Ga þ In) ratio as a function of depth in the absorber layer is desirable in a CIGS PV device in order to improve the separation of the photogenerated charge carriers and reduce recombination at the back contact. [6,7] Ability to tailor film composition is critical for achieving the desired grain structure and highest-efficiency PV device characteristics. Studies on vacuum-deposited Cu 1-z In 1-x Ga x Se 2-y S y films indicate that copper-poor films (0.05 z 0.12) with x % 0.3 are desired for highest-efficiency devices.…”