Kinetic Processes and Surfactant Design of Group I Elements on the CZTS (1̅1̅2̅) Surface

Abstract

Cu 2 ZnSnS 4 (CZTS) is a promising thin-film solar-cell material consisted of earth abundant and nontoxic elements. Yet, there exists a fundamental bottle neck that hinders the performance of the device due to complexed intrinsic defects properties and detrimental secondary phases.Recently, it was proven experimentally that Na and K in co-evaporation growth of CZTS can enlarge the grain size and suppress formation of ZnS secondary phase near surface, but the reasons are not well understood. We used first principle calculations to investigate the kinetic processes on CZTS ( 112 ) surface involving Group I elements, including Na, K, and Cs, to demonstrate their surfactant effects. Both the structure of the reconstructed surfaces involving Group I elements and various diffusion paths of a Zn ad-atom in these reconstructed surfaces were explored. The advantages and concerns of the surfactant effects of Na, K, Cs, were systematically compared and discussed. Although Group I elements protect Cu sites on the subsurface layer, a disordered metastable configuration with a diffusion barrier of about 400meV was found. Therefore, a precise control of growth condition is essential to avoid the metastable phase. In addition, our studies provide a systematical design principle for surfactant effects during the growth.

Hyperactive Selenium Source Yields Kesterite Solar Cells with 12.86% Efficiency

“…Notably, the presence of ZnSe is detected in the control sample, which is absent in the Na 2 (Se 2 S)−7.5 sample, indicating an improved diffusion of elements facilitated by liquid Cu 2‐x Se. The XRD pattern shows that the absorption layer with Na 2 (Se 2 S) shows the prior growth of the grain along the (112) crystalline plane, [ 39,40 ] which becomes more pronounced as the Na 2 (Se 2 S) content increases (Figure S8, Supporting Information).…”

“…[37,38] As the selenization proceeds at 550 °C, transitioning from the Na 2 (Se 2 S)−7. shows that the absorption layer with Na 2 (Se 2 S) shows the prior growth of the grain along the (112) crystalline plane, [39,40] which becomes more pronounced as the Na 2 (Se 2 S) content increases (Figure S8, Supporting Information).…”

Surface Purification and Compensation of I Interstitial in Quasi-2D CsPbI3

“…Meanwhile, it is attractive to remove I int at the fabrication stage by modifying the kinetics of crystal growth or post-annealing, especially surface kinetics. Surfactants can modify surface kinetics in various semiconductor systems and promote the atom diffusion. − For example, surfactants of Sb can enhance diffusion of N on GaN surface to facilitate the epitaxial step flow growth . Meanwhile, surfactants of Pb can promote interlayer diffusion of Mn incorporated into Si to enhance extrinsic doping .…”