Enhancement of photosensitivity in bismuth doped Cu₂ZnSnS₄ thin films

Abstract

In this paper, the effect of bismuth doping on the structural, morphological, optical and electrical properties of Cu2ZnSnS4 (CZTS) films has been investigated. The undoped and bismuth doped CZTS films (0, 0.5, 1, 1.5 and 2 mol%) were deposited on glass substrates by solution based method. The XRD result shows a significant improvement in the crystallinity of the films with increase in bismuth concentration. The Raman spectra of the films show the dominant peak at 334 cm–1 corresponding to A1 vibrational mode of CZTS kesterite phase. The FESEM micrographs of the films show an enhancement in the grain size and densification with the addition of bismuth ion concentration. The optical bandgap of the films was found to vary (1.59–1.40 eV) with the doping of bismuth ions. The I –V characteristics indicate twofold increment in the photoconductivity for the bismuth doped CZTS films under 100 mW/cm2 illumination suggesting their potential application in photovoltaic devices. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Progress and Perspectives of Thin Film Kesterite Photovoltaic Technology: A Critical Review

“…For convenience, a classification in three different types of extrinsic doping is possible: 1.Extrinsic doping with nonconventional elements: In, Bi, Sb, and Fe 2.Extrinsic doping with isoelectronic elements from the same family as Cu, Zn, and Sn: this includes Ag, Cd, and more extensively Ge…”

“…"> 2.Extrinsic doping with isoelectronic elements from the same family as Cu, Zn, and Sn: this includes Ag, Cd, and more extensively Ge 3.Extrinsic doping with alkaline elements: Li, Na, K, Rb, and Cs …”

“…This is an important finding since some buffer (In 2 S 3 ) and window (In 2 O 3 :SnO 2 , ITO) layers contain In, suggesting that some possible interdiffusion will not have a detrimental influence on the absorber's properties. Sb and Bi have also been studied and demonstrated interesting properties as possible crystallization flux agents, though unfortunately showing detrimental or no impact on the optoelectronic properties of the devices . In particular, Sb seems to strongly interact with Na, and under the presence of this codoping, to markedly increase the grain size .…”

“…Complementary to the last approach, doping with alkaline elements is another strategy that has shown a strong positive impact on kesterite. Li, Na, K, Rb, and Cs have been largely studied, and some recent works shed light on the important effect of these dopants. The bulk of this work is inherited from the CIGSSe community, with Na and K having been the first to be investigated.…”

Optimization of Cu2ZnSnS4 Absorber Layers via Sulfurization of Electrodeposited Cu-Zn-Sn Precursors for Photovoltaic Applications

“…Enhance grain growth and (112) orientation Increase in solar cell efficiency [154,158,160] Bismuth has been shown to work as a fluxing element, although it has been studied only to a limited extent for CZTS or CIGS materials [162][163][164]. These studies are in agreement on the occurrence of a growth modifier role of Bi with regard to CZTS and CIGS crystal growth;…”