Evaluating the role of composition and local structure on alkali out‐diffusion in glasses for thin‐film solar cells

Abstract

Fostered by the increasing demands for clean energy, thinfilm photovoltaic has drawn considerable research attention due to low material consumption and the rapid progress in the technology of cost-effective fabrication of thin films. 1-3 Inorganic compound semiconductors CuInGaSe 2 (CIGS) and Cu 2 ZnSnS 4 (CZTS) have been the most popular candidates as the absorber layer in thin-film solar cells due to their highly relevant optoelectronic properties. 1,4,5 Thin-film coatings on commercially available glass substrates for solar cells and optoelectronic devices have been widely studied. 6-8 Recently, apart from the optimization of the absorber films, many groups have undertaken studies highlighting the critical influence of the alkali ions diffusing from the substrates on the performance of the devices. 9-12 In the conventional architecture of the CIGS-and CZTS-based thin-film solar cells, besides providing mechanical support and high processing temperature, the substrate (most commonly used soda lime glass) doubles up as a source of Na that out-diffuses to the absorber layer via the bottom electrode (~1 μm thick Mo film). 13-16 Solar cells relying on the diffusion of Na

Efficiency enhancement of CZTSe solar cells based on in situ K-doped precursor

“…Hence, in situ K-doping enhances the Na diffusion from the Mo layer to the CZTS layer, and this diffusion process can be explained by a solid-state ion exchange mechanism between Na and K cations. 47…”

“…Hence, in situ Kdoping enhances the Na diffusion from the Mo layer to the CZTS layer, and this diffusion process can be explained by a solid-state ion exchange mechanism between Na and K cations. 47 Selenization annealing forms a U-shaped depth prole of Na in both absorbers (shown in Fig. 3g), but the doped absorber exhibits a lower level of Na in the bulk and a relatively higher level at the front and rear interfaces, resulting in a steeper gradient in the U-shaped Na distribution.…”

Crystallization mechanism and defect passivation of Cu2ZnSn(S,Se)4 thin film solar cells via in situ potassium doping

“…Nevertheless, it is insufficient to achieve effective doping only by K diffusion from the substrate due to its low content in the SLG substrate and poor diffusion ability. 30…”

“…Nevertheless, it is insufficient to achieve effective doping only by K diffusion from the substrate due to its low content in the SLG substrate and poor diffusion ability. 30 Post-deposition treatments such as spin coating 31,32 and vapor diffusion 24 are commonly used to dope K for CZTSSe cells prepared by sputtering or evaporation. In this work, a CZTS target doped with K is sputtered for incorporation, and a uniform distribution could be obtained in the precursor aer magnetron sputtering.…”

Non‐destructive analysis of concentration profiles in turbid media using micro‐spatially offset Raman spectroscopy: A physical model

“…The study of the concentration gradient of an agent which diffuses in turbid media is a topic transcending many fields of materials science. For instance, in the field of semiconductors, it is relevant in the study of the diffusion of dopants into silicon wafers [ 1 ] ; in solar cells technology, it is of interest for the study of the diffusion of alkali ions from the glass into the electrode films [ 2 ] ; in the pharmaceutical field, it is pertinent in studying the absorption of drugs or moisture in tablets, [ 3 ] drug release [ 4,5 ] and drug diffusion in human skin. [ 6 ] Overall, the knowledge of the diffusion profiles and associated dynamics of the process is crucial for the understanding of complex mechanisms underlying the diffusion processes, which strongly influence the properties of many materials.…”