Direct evidence of causality between chemical purity and band-edge potential fluctuations in nanoparticle ink-based Cu₂ZnSn(S,Se)₄ solar cells

Abstract

Guillaume (2019) Direct evidence of causality between chemical purity and band-edge potential fluctuations in nanoparticle ink-based Cu2ZnSn(S,Se)4 solar cells.

Underlying mechanism of the efficiency loss in CZTSSe solar cells: Disorder and deep defects

“…According to the reported information, such as the density and the carrier capture cross-section of the defects, measured by DLTS, here we can estimate the shortest carrier lifetime of CZTSSe by Equation (5). The calculated carrier lifetimes τ c are listed in Table 2 [89,90,101,[105][106][107][108][109][110][111][112]. Unexpectedly, the τ c values derived from the DLTS are in the order of microsecond or even millisecond, which is several orders of magnitude larger than the measured result (τ m ).…”

“…Campbell et al [107] detected a shallow donor (3.2±0.5 meV) for Sn Cu and a shallow acceptor (38.3±3.8 meV) for V Cu , and neither of them had been detected by the DLTS. In addition, Campbell et al [107] calculated the density of the donoracceptor-pair (Sn Cu and V Cu ) to be 2.1×10 18 cm −3 from the blue-shift value of excitation-dependent PL spectra. Luckert et al [111] studied pure CZTSe, for which two activation energies of E a1 =7±2 meV and E a2 =27±3 meV were determined.…”

“…Qi et al [106] also detected Cu Zn and Cu Sn defects by conventional C-DLTS, with the E a of 175 and 366 meV, respectively. Campbell et al [107] calculated the E a1 to be 86±7 meV according to a broad DLTS peak at around 115 K ( Fig. 12d and e).…”

“…Besides, other shallower defects beyond the scope of DLTS were detected by TPL, which will be mentioned below. In the meantime, Campbell et al [107] acquired the minority carrier lifetime (0.20 ns) and minority carrier diffusion length (203 nm) of the CZTSSe film by relevant photoelectric measurement and analysis. We can see from these different reports that there is still no convincing understanding on the defects because the experimental identification of defects has strong subjectivity.…”

“…One was classified as the potential fluctuation with a smaller energy level (25-30 meV), and the other was considered as a donor defect with its activation energy of 120-130 meV. Campbell et al [107] detected a shallow donor (3.2±0.5 meV) for Sn Cu and a shallow acceptor (38.3±3.8 meV) for V Cu , and neither of them had been detected by the DLTS. In addition, Campbell et al [107] calculated the density of the donoracceptor-pair (Sn Cu and V Cu ) to be 2.1×10 18 cm −3 from the blue-shift value of excitation-dependent PL spectra.…”