Solution-Based Synthesis and Characterization of Cu₂ZnSnS₄ Nanocrystals

Abstract

Recent advances have been made in thin-film solar cells using CdTe and CuIn(1-x)Ga(x)Se(2) (CIGS) nanoparticles, which have achieved impressive efficiencies. Despite these efficiencies, CdTe and CIGS are not amenable to large-scale production because of the cost and scarcity of Te, In, and Ga. Cu(2)ZnSnS(4) (CZTS), however, is an emerging solar cell material that contains only earth-abundant elements and has a near-optimal direct band gap of 1.45-1.65 eV and a large absorption coefficient. Here we report the direct synthesis of CZTS nanocrystals using the hot-injection method. In-depth characterization indicated that pure stoichiometric CZTS nanocrystals with an average particle size of 12.8 +/- 1.8 nm were formed. Optical measurements showed a band gap of 1.5 eV, which is optimal for a single-junction solar device.

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

“…Preliminary simulation reveals that such NCs hold a wurtzite phase, which is totally different from the well-characterized stannite and kesterite phase in both JCPDS database and previous reports. [20][21][22]25 The experimental pattern of the CZTSe NCs matches well with the simulated one of wurtzite structure with a¼4.00 Å and c¼6.61 Å , which are smaller than those of CuInSe 2 . 8 To investigate the formation mechanism of the wurtzite CZTSe NCs, some control experiments were carried out.…”

“…In addition, CZTSe films have promising thermoelectric properties, with large thermoelectric figure of merit values of about 0.9 at 860 K. 19 Several solution-based methods have been reported to synthesize nearly stoichiometric Cu 2 ZnSnS 4 NCs. [20][21][22] The conversion efficiency of the Cu 2 ZnSnS 4 -absorber films prepared by co-sputtering, which added cost to the process, has reached over 6.7%. 23 Moreover, Cu 2 ZnSnS x Se 4-x -based thin-film solar cells with power conversion efficiency of 9.6%, a level suitable for possible commercialization, have been constructed by solution method using toxic and unstable hydrazine.…”

“…8,13,14,27,28 The reported Cu 2 ZnSn(S,Se) 4 NCs mostly show the stannite or kesterite structures. [19][20][21][22]25 Recently, Li and coworkers 26 reported the Cu 2 ZnSnS 4 NCs with wurtzite structure, which has been found in many binary and ternary chalcogenides, but seldom in quaternary compounds. 8,13,14,29,30 The wurtzite structure owns disordered cations, and the random distribution of A and B ions in the wurtzite phase offers the flexibility for stoichiometry control, which is advantageous for the fabrication of photovoltaic devices, as it provides the ability to tune energy band gap for device optimization.…”

A comparative study on charge carrier recombination across the junction region of Cu2ZnSn(S,Se)4 and Cu(In,Ga)Se2 thin film solar cells

“…2,3 Replacing In and Ga in CIGS with earth-abundant Zn and Sn, we can obtain Cu 2 ZnSn(S x Se 1−x ) 4 (CZTSSe) which has drawn increased attention as an alternative absorber layer. [4][5][6][7][8][9] CZTSSe has optimal band gap (1.0-1.5 eV, depending on the S, Se compositions), 10 and also high absorption coefficient (∼10 4 cm −1 ) that make it suitable for solar cell application. 11 Nevertheless, the highest achieved efficiency, so far, using CZTSSe is 12.6%, 12 which is only about half of the similar structured CIGS-based solar cell.…”

Strain tuning of native defect populations: The case of Cu2ZnSn(S,Se)4

“…[1][2][3][4][5][6][7][8][9][10][11] Doping and recombination in the CZTSSe absorber layer are believed to be largely determined by its native defects. 11 In its close relative, Cu(In,Ga)(S, Se) 2 (CIGSSe), Cu vacancies (V Cu ) are the dominant native defects and act as important shallow acceptors.…”