Molecular routes to Cu2ZnSnS4: A comparison of approaches to bulk and thin-film materials

Abstract

A range of xanthates (R′3P)2CuS2COR [R′ = Ph, R = Et (1), i-Pr (2), t-Bu (3), t-Amyl (4); R′ = PhO, R = Et (5), R′ = n-Bu, R = Et (6), Bun (7)], M(S2COR)2 [M = Sn R = Et (8); Zn, R = Et (10), i-Pr (11), n-Pr (12), n-Bu (13), n-Hex (14)], Sn(S2COEt)4 (9), Zn(S2COEt)2.TMEDA (15) have been synthesised and their thermal decomposition profiles delineated by TGA. A parallel range of dithiocarbamates (R′3P)2CuS2CN(Me)R [R′ = Ph, R = Bun (16), Bz (17)], M[S2CN(Me)R]2 [M = Sn, R = Bun (18), Bz (19); M = Zn, R = Bun (21), Bz (22)] has been similarly assessed. Although precursor combinations have been found from these systems that generate Cu2ZnSnS4 (CZTS) from either a bulk decomposition (1, 8, 10 at 400 °C/Ar; Cu2Zn1.02Sn0.74S4.6), from a doctor-bladed film (7, 8, 13 at 400 °C/Ar; Cu2Zn1.2Sn1.0S3.6), and as nanoparticles (7, 8, 13 in octadecane/oleic acid, 150 °C; Cu2Zn1.0Sn0.7S2.6), attempts to deposit CZTS by aerosol-assisted CVD has proved more challenging and only successful from the dithiocarbamates 16, 18, 21 (350 °C; Cu2Zn0.9Sn0.7). As part of this work the crystal structures of 2–5, 8, 16, and the dithiocarbamate decomposition product {Sn[S2CN(Me)Bun)]2S}2 (20) have been determined.