Time-resolved photoluminescence properties of CuInS2/ZnS nanocrystals: Influence of intrinsic defects and external impurities

Abstract

Photoluminescence (PL) lifetime studies of CuInS2 nanocrystals (NCs) are carried out after synthesizing core-shell and compositionally variant structures using time-resolved PL spectroscopy. Long-lived excited state decay times are observed for the NCs, and decay times are very much dependent on the size of the CuInS2 NCs. The emission bands are attributed to the surface (shorter PL lifetime) and defect (longer PL lifetime) related trap states, respectively. The decay dynamics of the CuInS2 NC’s excited-state carriers is very sensitive to the surface, intrinsic defects, and extrinsic impurities. The observed large Stokes shifts and broad PL spectra also reveal the involvement of the defect-related trapping sites in the emission process.

Bicolor Mn-doped CuInS2/ZnS core/shell nanocrystals for white light-emitting diode with high color rendering index

“…In contrast to the direct recombination of electrons and holes in II-VI nanocrystals, the defect-related donor-acceptor transition and the surface-related recombination are dominant in CIS nanocrystals. The fast decay component (s 1 ) may be assigned to the recombination from the surface-related state, 22,23 and the other two slow decay components (s 2 and s 3 ), which account for a large amount (87%-96%) of the total PL spectra, may be attributed to the defect-related donor-acceptor transition. 22,23 The average lifetime (s av ¼ P n A n s 2 n = P n A n s n Þ is $470 ns for the CIS core, and it is increased to $580 ns as the CIS core is passivated with the first ZnS shell.…”

“…The fast decay component (s 1 ) may be assigned to the recombination from the surface-related state, 22,23 and the other two slow decay components (s 2 and s 3 ), which account for a large amount (87%-96%) of the total PL spectra, may be attributed to the defect-related donor-acceptor transition. 22,23 The average lifetime (s av ¼ P n A n s 2 n = P n A n s n Þ is $470 ns for the CIS core, and it is increased to $580 ns as the CIS core is passivated with the first ZnS shell. However, it is reduced to $410 ns after the Mn 2þ ions are adsorbed on the surface of CIS/ZnS NCs and the NC's PL QY is significantly decreased also because Mn 2þ ions on the surface of CIS/ZnS NCs could promote the energy migration from Mn 2þ ions to the surface quench centers.…”

Mercaptophosphonic acids as efficient linkers in quantum dot sensitized solar cells

“…For comparison, QDs deposited on TiO 2 without linker are also plotted. 68,70,71 Accordingly, the observed fast (13 ns) and slower decay components (93 ns, 486 ns) can be attributed to radiative recombination processes of QD surface defect states and of defect related donor-acceptor pairs, respectively. 7, PL quenching strongly depends on the nature and length of the linker.…”

“…7 shows time-resolved PL decay curves of QDs without electron-accepting NMOs deposited on SiO 2 (black dots) and QDs with different linkers (MPA, MEPA and MUPA) deposited on TiO 2 as a function of time. 68,[70][71][72][73][74] For our decays the three component lifetimes were 13, 93 and 486 ns for CuInS 2 nanoparticles on SiO 2 without electron-accepting NMOs, the details about the tting parameters are given in Table S1, ESI. As shown by Fig.…”

“…7, PL quenching strongly depends on the nature and length of the linker. 71 These donor and acceptor states in ternary CuInS 2 nanocrystals are believed to appear due to In, Cu antisite defects or sulfur vacancies. This decay behaviour is consistent with previously reported studies of charge transfer dynamics on linker length.…”