Cu2ZnSnS4 QDs anchored 2-D few-layer graphene bridge enhanced photo induced charge carrier transport behavior for high efficient kesterite photovoltaic cell

Abstract

Quaternary chalcogenide Cu2ZnSnS4 (CZTS) is a promising absorber for photovoltaic cell application due to its excellent properties like natural abundancy, non-toxic material incorporation, high absorption coefficient ∼104 cm−1 and tuneable band gap energy of 1.4–1.6 eV. However, still there is a huge gap of efficiency between the market oriented Si based photovoltaic device and kesterite device as it is hindered by poor charge carrier mobility. To improve the carrier mobility of semiconducting CZTS material, incorporation of highly conducting material like graphene would be helpful. The incorporation of graphene into CZTS enhances the separation and transfer of charge carriers in an efficient way inhibiting recombination. In this present work, the photovoltaic performance of solution processed single phase kesterite CZTS QDs anchored on electro-chemically prepared few-layer graphene sheet (FLGS) as active layer has been reported. The QD decoration has been carried out by a simple, scalable, environment friendly solution based approach without surface modifications and post-sulphurization treatment. The prepared hybrid structure demonstrates significant increase in photocurrent and optical absorbance indicates the fast charge carrier transport behaviour. The power conversion efficiency (PCE) of fabricated hybrid CZTS QDs-FLGS photovoltaic cell with device configuration of Mo/CZTS QDs-FLGS/CdS/ZnO/Al approached ∼7.64% (for 2.5 wt% FLGS loading) with short circuit current density (Jsc) of 19.07 mAcm−2, superior to individual CZTS QDs (∼6.11% PCE and 15.6% Jsc).