Ultrafast glimpses of the excitation energy-dependent exciton dynamics and charge carrier mobility in Cs₂SnI₆ nanocrystals

Abstract

Advancements in photovoltaic research suggest tin-based perovskites as potential alternatives to traditional lead-based structures. Cs2SnI6, specifically, stands out as a notable candidate, exhibiting impressive performance. Nevertheless, its complete potential remains...

The Prospects and Challenges for Ambi‐polar Vacancy‐Ordered Double‐Perovskite Cs2SnI6 Toward Realization of High‐Efficiency Air‐Stable Solar‐Cells

“…{CsI þ SnI 2 þ I 2 -, [16] CsI þ SnI 2 -, [35,36,46,[67][68][69] CsI þ SnI 4 - [32,38,46,[70][71][72] }; Solution based methodnanocrystal! { [18,73,[76][77][78][79][80]87,89] }; Vacuum based method {AACVD-, [14] Co-evaporation-, [81][82][83] 2-Step method- [29,33,34,45,[84][85][86] }. The asterisk sign represents usage of additional HI precursor during synthesis.…”

“…The exciton dynamics in Cs 2 SnI 6 nanocrystals were recently studied by G. Kaur et al using the steady-state absorption spectroscopy technique with a reported experimental band-gap value of 1.71 eV, and the presence of two distinct exciton peaks A and C at energies E A = 1.93 eV and E C = 3.44 eV, respectively, along with a less prominent B peak corresponding to E B = 2.74 eV (see Figure 2a) is identified. [87] The physical origins of the same are ascribed to specific transitions (V j C k ) from jth valence band (V) to kth conduction band) in its theoretically calculated electronic band structure, where j = 1 corresponds to the highest occupied band and k = 1 points to the lowest unoccupied band (see Figure 2b). The theoretical band-gap calculations reveal a band-gap of 1.03 eV, and the appearance of A, B, and C excitonic peaks is due to V 2 C 1 transition at Γ-point for peak-A (E A = 1.45 eV); V 4 C 1 transition at L-point for peak B (E B = 2.30 eV); and V 10 C 1 transition at X-point for C-peak (E A = 3.7 eV), respectively.…”

“…Apart from the growth-related conditions, the scatter in the experimental reported band-gap may be due to the complex absorption spectra of Cs 2 SnI 6 , which shows multiple excitonic absorption peaks. [30,31,87] There are contrasting experimental reports of absorption spectra, both with the presence [32,36,60,67,68,87,88] and absence [14,18,19,33,34,38,62,63,69,73,77,85,89] of exciton peaks in Cs 2 SnI 6 . The exciton dynamics in Cs 2 SnI 6 nanocrystals were recently studied by G. Kaur et al using the steady-state absorption spectroscopy technique with a reported experimental band-gap value of 1.71 eV, and the presence of two distinct exciton peaks A and C at energies E A = 1.93 eV and E C = 3.44 eV, respectively, along with a less prominent B peak corresponding to E B = 2.74 eV (see Figure 2a) is identified.…”

“…The apparent difference between theoretical and experimental values for A-excitonic peak is due to the presence of inversion-induced parity-forbidden transitions and exclusion of excitonic effects in the theoretical calculations. [87] The presence/absence of excitonic peaks in absorption spectra is sensitive to the specific conduction band state occupancies (filled/vacant) that participate in the transition. The presence of intrinsic or extrinsic defects that arise during growth conditions may smear out the conduction band or valence band states, hindering the appearance of exciton peaks in the steady-state absorption spectrum.…”