Wurtzite Cu2ZnSnSe4 nanocrystals for high-performance organic–inorganic hybrid photodetectors

Abstract

Indium-free quaternary chalcogenide, Cu2ZnSnSe4 (CZTSe), has driven much attention for its potential application in photovoltaics and optoelectronics. It is well known that the composition and structure of nanocrystals (NCs) significantly affect their optical and electrical properties. Controllable synthesis of materials with new crystal structures, especially metastable structures, has given impetus to the development of nanomaterials with many new exciting properties and applications. High-quality CZTSe NCs with thermodynamically metastable wurtzite phase and optical band gap of 1.46 eV were herein synthesized via a facile, lost-cost and safe-solution method. The formation mechanism of the wurtzite CZTSe NCs was investigated in detail, which indicates high reaction rate and low surface energy are favorable for the formation of wurtzite structure. The promising application of as-synthesized NCs in photovoltaics and optoelectronics has been demonstrated by the high-performance hybrid photodetector made from CZTSe NCs and P3HT, with an on/off ratio larger than 150. Yu-Guo Guo, Li-Jun Wan and co-workers have prepared CZTSe nanocrystals with a ‘wurtzite’ structure in a simple, cost-effective synthesis at relatively low temperature. While there is currently an efficient component in photovoltaic and optoelectronic devices made of copper, indium and selenium, indium is in limited supply and there is a concerted effort to discover an alternative. By heating some precursors together in solution, cooling down the mixture and then adding a solvent, the team obtained the quarternary chalcogenide Cu2ZnSnSe4 (CZTSe) in a wurtzite form — a metastable structure which typically offers tunable properties that are well suited to photovoltaic applications. Indeed, when incorporated with poly(3-hexylthiophene) (P3HT) the new material showed a good photoresponse — a rapid, sensitive switch between ‘on’ and ‘off’ states - that subsequently served to construct a high-performance photodetector. Indium-free quaternary chalcogenide, Cu2ZnSnSe4 (CZTSe), has driven much attention for its potential application in photovoltaics and optoelectronics. High-quality CZTSe nanocrystals (NCs) with thermodynamically metastable wurtzite phase were herein synthesized via a facile, lost-cost and safe-solution method, in which high reaction rate and low surface energy are favorable for the formation of wurtzite structure. The promising application of the as-synthesized NCs in photovoltaics and optoelectronics has been demonstrated by the high-performance hybrid photodetector made from CZTSe NCs and P3HT.