Distinctive Deep‐Level Defects in Non‐Stoichiometric Sb₂Se₃ Photovoltaic Materials

Abstract

Characterizing defect levels and identifying the compositional elements in semiconducting materials are important research subject for understanding the mechanism of photogenerated carrier recombination and reducing energy loss during solar energy conversion. Here it shows that deep‐level defect in antimony triselenide (Sb2Se3) is sensitively dependent on the stoichiometry. For the first time it experimentally observes the formation of amphoteric SbSe defect in Sb‐rich Sb2Se3. This amphoteric defect possesses equivalent capability of trapping electron and hole, which plays critical role in charge recombination and device performance. In comparative investigation, it also uncovers the reason why Se‐rich Sb2Se3 is able to deliver high device performance from the defect formation perspective. This study demonstrates the crucial defect types in Sb2Se3 and provides a guidance toward the fabrication of efficient Sb2Se3 photovoltaic device and relevant optoelectronic devices.

Interfacial Engineering towards Enhanced Photovoltaic Performance of Sb2Se3 Solar Cell

“…In the Raman spectrum (Figure S6a, Supporting Information), the peaks at 152, 189, and 209 cm −1 correspond to the vibrations of Sb-Sb, Se-Sb-Se, and Se-Se bonds of Sb 2 Se 3 , respectively. [14] No Raman peak corresponding to Sb 2 O 3 was observed, which also indicates the phase purity of the obtained Sb 2 Se 3 film. The texture coefficient (TC (hkl) ) of Sb 2 Se 3 films on Sb-CdS and Cd-CdS substrates was calculated to examine the preferential crystallite alignment of the deposited Sb 2 Se 3 films according to the following equation: [15] / 1 0 1 0…”

“…Combined with the theoretical calculation results, [21a,b,e,f,22] traps H1 and H2 located at ≈0.68 and 0.77 eV above the VBM (Figure 7c,d) can be classified as antimony vacancy (V Sb ) and selenium antisite defects (Se Sb ). [14] DLTS characterization reveals the nature of deep defects in Sb 2 Se 3 films. By comparing the activation energies of these trap defects, we find that they are similar in the two devices, indicating that the origins of these defects are the same.…”

“…This means that carrier recombination of devices treated with SbCl 3 can be effectively inhibited. [14] Transient absorption spectroscopy (TAS) was further performed to compare the kinetics of carrier transport at the different ETL/Sb 2 Se 3 interfaces. We monitored the evolution of TAS spectra of two different samples excited by 360 nm laser pulses.…”

Revealing the chemical structure-dependent carrier trapping in one-dimensional antimony selenide photovoltaic materials

“…It was reported that point defects are easy to form in the Sb 2 Se 3 lattice in both the experimental results and first-principles calculations. 24,25 Here, we attribute the dynamic decay to defect-induced recombination at a low excitation intensity, which is common in semiconductor materials and extremely likely to take place due to the low defect formation energy. 24–27 Unexpectedly, the TA decays rapidly at higher excitation intensity, which corresponds to a larger photoexcited carrier density.…”

“…24,25 Here, we attribute the dynamic decay to defect-induced recombination at a low excitation intensity, which is common in semiconductor materials and extremely likely to take place due to the low defect formation energy. 24–27 Unexpectedly, the TA decays rapidly at higher excitation intensity, which corresponds to a larger photoexcited carrier density. This unusual recombination mechanism will be discussed later.…”