Identification of Excitons and Biexcitons in Sb₂Se₃ under High Photoluminescence Excitation Density

Abstract

abundant and low-cost elements like Cu, Zn, Sn, S, and Se, are also potential candidates for next-generation PV technologies. [3,4] However, kesterites have turned out to be very challenging on their way toward highly efficient thin film PV due to strong recombination of photogenerated charge carriers via various routes leading to short minority carrier lifetime (i.e., magnitude lower than in CIGS, CdTe, etc.) and diffusion length and resulting in large open circuit voltage deficit of kesterite solar cells. [3,[5][6][7][8] It is, therefore, obvious that more research is required to find the alternative inexpensive and earth abundant materials for efficient thin-film solar cells. One of the promising absorber material candidates among the inorganic semiconductors being in the spotlight these days is antimony triselenide (Sb 2 Se 3 ). The efficiencies of the corresponding thin-film solar cells have already boosted to 9.2% in a very short time. [9][10][11] Quasi-1D antimony triselenide belongs to a family of inorganic binary A V -B VI compounds and indeed has very attractive properties, such as proper optical bandgap (1.1-1.2 eV) for a solar absorber, a single phase structure, high light absorption coefficient (10 5 cm −1 ), low toxicity, and high element abundance. [12] It was shown that due to the very high absorption coefficient the photons with wavelengths λ > 800 nm are completely absorbed within the first 400 nm of Sb 2 Se 3 film, enabling much thinner absorber layers compared to the usual thin film solar cells. [13] Despite extensive research there are still problems related to various point defects or electronic band structure of this compound. Capacitance spectro scopy studies have shown the presence of various deep donor and acceptor defects. [14,15] Defect states in polycrystalline Sb 2 Se 3 have been studied also using temperature and laser intensity-dependent photoluminescence (PL). [16] The low-temperature (T = 10 K) PL spectrum was consisted of three bands at 0.94, 1.10, and 1.24 eV. The PL bands at 1.24 and 0.94 eV were found to originate from the distant and close donor-acceptor pair recombination, respectively, and the third PL band at 1.10 eV was proposed to be related to the grain boundaries. Recent theoretical calculations showed that the defect chemistry of quasi-1D Sb 2 Se 3 is rather complicated compared to conventional semiconductors. In particular, it has been discussed that the identical defects located on nonequivalent atomic sites might have different properties. [17] All kinds of defect studies are therefore extremely important as usually defects act as powerful recombination channels and reduce the performance of the solar cell.The near-band-edge emission of Sb 2 Se 3 microcrystals is studied in detail under high photoluminescence excitation density using a pulsed UV laser (λ = 266 nm, pulse width 0.6 ns). Based on the peak energy positions and the excitation power density and temperature dependencies (T = 3-110 K) of the photoluminescence spectra, the emission is interpreted as a reco...

Sb2Se3 Thin‐Film Solar Cells Exceeding 10% Power Conversion Efficiency Enabled by Injection Vapor Deposition Technology

“…The location of PL1 at 1.295 eV is very close to the energy bandgap of Sb 2 Se 3 (1.316 eV at 20 K) [ 17 ] and can therefore be attributed to the near‐band exciton transition. [ 18 ] The emission peak of PL2 at 1.208 eV and PL3 at 0.924 eV are defect‐related transitions, such as free‐to‐bound state, or donor‐acceptor pair transitions. [ 19 ] The PL1, PL2, and PL3 for CSS Sb 2 Se 3 nanorod arrays exhibit similar positions, but slightly higher peak intensities (Figure 4b).…”

Efficient defect-driven cation exchange beyond the nanoscale semiconductors toward antibacterial functionalization

“…Using Arrhenius plots (Fig. 1d) and Supplementary Equation 1, we established that all band-related activation energies were no greater than 30 meV [26]. Considering the positions of the detected emission peaks, which lie quite distant from the low-temperature band gap energy of 1.32 eV reported for Sb2Se3 [27], and the obtained modest thermal activation energies, all the observed PL bands most probably originate from deep donor-deep acceptor (DD-DA) pair recombination [28,29].…”

Photoreflectance and Photoluminescence Study of Antimony Selenide Crystals

“…In addition, Sb 2 Se 3 is stated to be an indirect bandgap semiconductor which again leads to low PL emission, whereas for the PR study high-crystalline quality samples are required. Recently, broad defect-related PL emission was observed in Sb 2 Se 3 microcrystals under continuous-wave (CW) excitation and biexcitonic/excitonic under high excitation density. , …”

“…Recently, broad defect-related PL emission was observed in Sb 2 Se 3 microcrystals under continuous-wave (CW) excitation and biexcitonic/excitonic under high excitation density. 15 , 16 …”