Elucidation of the Excited-State Dynamics in CuInS₂ Thin Films

Abstract

Transient absorption (TA) and photoluminescence spectroscopy have been performed on spray-deposited CuInS2 thin films. Sulfur and indium vacancies introduce electronic states in the bandgap located at 1.5 and 0.15 eV above the valence band, respectively. Deep donor and deep acceptor doublet states at 1.1 and 0.2 eV are assigned to copper/indium antisite defects. The excited-state dynamics, which are derived from TA experiments, show electronic coupling between indium antisite defects and indium vacancies. The Shockley, Read, and Hall recombination model has been modified to account for this coupling and to simulate the TA results. Furthermore, the lifetime of the 1.1 eV state is found to be 20−50 μs, which is related to the low photovoltage of CuInS2 based solar cells.

Optimization of the recipe for the synthesis of CuInS2/ZnS nanocrystals supported by mechanistic considerations

“…Literature information [17,20,21,[43][44][45][46][47] on the different mechanisms of emissions can be compiled into the comprehensive emission model presented in Figure 4. As shown in Figure 4, besides excitonic emission [1(a), 1(b) and (2)], defects such as atom vacancy (V s ··, V In ″′, V Cu ′), indium or copper interstitial (In i ···, Cu i ··), and indiumcopper antisite (Cu In ″, In Cu ··) can also generate emission through the recombination with band (conduction or valance band) or between defects.…”

Noninjection, one-pot synthesis of Cu-deficient CuInS2/ZnS core/shell quantum dots and their fluorescent properties

“…Compared with a small Stokes-shift (<100 meV) observed from II-VI-based QDs [8], the emission peaks of CIS QDs are significantly red-shifted relative to their absorption peaks. Such a broad emission and a large Stokes-shift could be ascribed to the presence of deep defect states in the band gap, resulting in the donor-acceptor pair (DAP) recombination [6,10,11,14,15]. These deep traps can be a sulfur vacancy (V S ), an interstitial copper (Cu i ), and an indium substituted at a copper site (In Cu ) as donor states, and a copper vacancy (V Cu ), an indium interstitial (In i ), and a copper substituted at an indium site (Cu In ) as acceptor states.…”

“…These deep traps can be a sulfur vacancy (V S ), an interstitial copper (Cu i ), and an indium substituted at a copper site (In Cu ) as donor states, and a copper vacancy (V Cu ), an indium interstitial (In i ), and a copper substituted at an indium site (Cu In ) as acceptor states. The particular type of these donor and acceptor states would depend on the stoichiometry of CIS, i.e., Cu-rich versus In-rich phases [10,14,[16][17][18], determining the dominant DAP recombination pathway. The population density of such defects can also be readily controllable in colloidal routederived CIS QDs.…”

Spray-deposited CuInS2solar cells

“…Another advantage of In 2 S 3 over CdS is its slightly larger bandgap. Detailed investigations of the interface between TiO 2 and CuInS 2 as well as on the role of the buffer material can be found in [15,16].…”