Impact of alloying duration of an electrodeposited Cu/Sn/Zn metallic stack on properties of Cu₂ZnSnS₄ absorbers for thin‐film solar cells

Abstract

The impacts of preheating of an electrodeposited Cu/Sn/Zn (CTZ) stack precursor on structural changes of the CTZ precursor and the impact on structural and electric properties of the finally obtained Cu 2 ZnSnS 4 (CZTS) films are discussed in detail. We found that preheating for relatively long durations improved the qualities of CZTS films: these films were composed of large grains and had compact and flat surface morphologies. The best solar cell with efficiency of 8.1% was obtained on the basis of a CZTS film derived from the CTZ precursor preheated for 200 min. The external quantum efficiency response of the cell indicated efficient utilization of photons with relatively long wavelength regions because of its good structural and electronic properties. On the other hand, a short circuit current density-temperature property of one of the best cells in this study suggested that the CZTS film had deep acceptor levels and/or an appreciable energy barrier to the Mo back contact. Moreover, an open circuit voltage-temperature property of the corresponding device showed activation energy of 1.18 eV, indicating preferential occurrence of CdS-CZTS interface recombination.

Co‐Electrodeposited Cu2ZnSnS4 Thin Film Solar Cell and Cu2ZnSnS4 Solar Cell – BiVO4 Tandem Device for Unbiased Solar Water Splitting

“…The crossover phenomenon in J – V curves also indicated that an obvious back contact barrier exists at the interface between Mo and CZTS . Since the best η of co‐electrodeposited CZTS‐based solar cells was reported as 7.23%, the efficiency obtained in this study represents the highest value, even though this value is still lower than our previously reported electrodeposited CZTS‐based solar cell using a three‐step electrodeposited Cu/Sn/Zn multilayer precursor (7.99%, 8.14%) . Figure b shows the external quantum efficiency (EQE) for the best CZTS solar cell in this work.…”

“…By establishing a sufficiently long prealloying time, which improves the growth of the Cu‐Sn and Cu‐Zn alloys in the stack precursor of Cu/Sn/Zn, we obtained high‐quality CZTS films. Based on these CZTS photoabsorbers, we obtained new record‐breaking efficiencies for electrodeposited CZTS solar cells of 7.99 and 8.14% . Compared to the three‐step electrodeposited Cu/Zn/Sn multi‐layer stack method (method (A)), approach (B) is much easier to implement due to the simplicity of the one‐step synthesis of the Cu‐Zn‐Sn mixed monolayer metallic precursor.…”

“…Based on these CZTS photoabsorbers, we obtained new record-breaking efficiencies for electrodeposited CZTS solar cells of 7.99 and 8.14%. [18][19] Compared to the three-step electrodeposited Cu/ Zn/Sn multi-layer stack method (method (A)), approach (B) is much easier to implement due to the simplicity of the onestep synthesis of the Cu-Zn-Sn mixed monolayer metallic precursor. Until now, the highest efficiency of co-electrodeposited CZTS solar cells was 7.3%, which was reported by J.…”

“…[30] Since the best η of co-electrodeposited CZTSbased solar cells was reported as 7.23%, [20] the efficiency obtained in this study represents the highest value, even though this value is still lower than our previously reported electrodeposited CZTS-based solar cell using a three-step electrodeposited Cu/Sn/Zn multilayer precursor (7.99%, 8.14%). [18,19] Figure 3b shows the external quantum efficiency (EQE) for the best CZTS solar cell in this work. The EQE value is more than 80% in the range of 530-660 nm but has a gradual decay as the wavelength increases toward the band edge (ca.…”

Understanding quaternary compound Cu2ZnSnSe4 synthesis by microscopic scale analyses at an identical location

“…It was shown that thanks to this soft annealing process, more uniform and less rough 22 Kesterite films can be obtained after the selenization step, leading to higher device efficiency 23 . Figure 1b) shows a top view SEM image of the position of interest after soft annealing at 350°C for 30 min.…”