Mitigation of Surface Oxidation in Sb₂Se₃ Thin Films Via Te Doping: An Effective Strategy Towards Realization of Efficient Electronic Devices

Abstract

Sb2Se3 and Te-doped Sb2Se3 films of ∼250 nm film thickness were deposited using a facile thermal evaporation technique from the bulk powder synthesized via the melt quenching technique. Thermogravimetric analysis of pure and Te-doped Sb2Se3 alloys in bulk form indicates decomposition of the alloys in the 303–673 K temperature range. The X-ray diffraction pattern revealed single-crystalline orthorhombic phase stabilization of as-prepared alloys in bulk as well as in the annealed thin films. Phase formation is also evident in the recorded Raman spectra from the appearance of two peaks at ∼189 and 210 cm–1, which are ascribed to the Sb2Se3 Ag mode. The absorbance spectra of as-annealed pure Sb2Se3 and Te-incorporated Sb2Se3 films exhibit significant reduction with Te doping due to an increase in the optical band gap. The conductivity in as-annealed Sb2Se3 and (0.08%)­Te-doped Sb2Se3 films recorded from 308 K (room temperature) to 392 K show a decrease in DC conductivity and activation energy with the insertion of Te in the Sb2Se3 system. Such a trend in conductivity and activation energy is attributed to arise as a result of structural changes as well as defect passivation enabled by Te insertion in the alloy. Interestingly, the DC conductivity is in the range of ∼10–7 Ω–1 cm–1 at 308.5 K, which is 10 times higher than that of the previously reported conductivity of Sb2Se3 films. Presently, the nonpreferential grain growth, undesirable deep-level defects, and surface oxidation in Sb2Se3 thin films are pressing issues that render them unsuitable for practical application in devices. Herein, this study brings to the fore a strategy to overcome these issues by doping Te in Sb2Se3 thin films, and hence it is a step forward towards the replacement of environmentally toxic CdTe-based devices.

Defect engineering in antimony selenide thin film solar cells

“…Another study of Te doping in Sb 2 Se 3 solar cells was reported by employing the thermal evaporation technique. 71 As compared to the control device without doping, the device with an optimal doping concentration of 0.08 at% showed an unusual increase in optical band gap from 1.46 to 1.65 eV, which was then ascribed to the crystallization of multiple Sb–Se phases with higher bond energies. However, the conductivity of doped films was reduced to 1.22 × 10 −7 Ω −1 cm −1 compared to undoped Sb 2 Se 3 2.55 × 10 −7 Ω −1 cm −1 .…”

“…10,31,39,67 Whereas Hobson et al revealed unintentional introduction of chlorine (Cl) impurities present in the purchased source material formed n-type Sb 2 Se 3 absorber. 36 Furthermore, due to the presence of extrinsic dopants such as iodine (I) 44,68 and tellurium (Te), 32,[69][70][71] the possibility of formation of n-type devices with high efficiencies also exists. Hence, it's vitally important to consider the source of the Sb 2 Se 3 material and any impurities that may be present in the growth or processing environment, as Sb 2 Se 3 in solar cells can behave as both p-type or n-type absorbers.…”

One-step Hydrothermal Synthesis of Sn-doped Sb2Se3 for Solar Hydrogen Production

“…Doping is an effective strategy for modifying physical and electronic properties by generating benign defects, improving conductivity, regulating crystallization, and suppressing surface or grain boundary defects. Various types of dopants including Na, [7] Fe, [8] K, [9] Te, [10] S, [11] , Bi, [12] and Cu, [13,14] have been extensively explored to improve the solar cell and PEC performance of Sb2Se3 photocathodes. For example, Te doping in Sb2Se3 solar cells, prepared through spincoating, has been shown to effectively suppress deep-level defects by regulating the atomic ratio of Se/Sb.…”

Tellurium Doping Inducing Defect Passivation for Highly Effective Antimony Selenide Thin Film Solar Cell

“…Ma et al [ 13 ] reported Te-doped Sb 2 Se 3 thin film synthesized by spin-coating, which indicated that Te-doping can successfully minimize the deep-level defects in the Sb 2 Se 3 thin film by optimizing the change in Sb/Se atomic ratios. Rahman et al [ 14 ] studied the Te-doped Sb 2 Se 3 thin film obtained by thermal evaporation from the bulk powder prepared using the melt quenching technique. A reduction in surface oxidation may be detected in Sb 2 Se 3 thin films, and the DC conductivity of the Te-doped Sb 2 Se 3 thin film is in the region of 10 −7 Ω −1 cm −1 at 308.5 K, which is ten times more than the conductivity of pristine Sb 2 Se 3 films that had previously been reported.…”

“…Rahman et al [14] studied the Te-doped Sb 2 Se 3 thin film obtained by thermal evaporation from the bulk powder prepared using the melt quenching technique. A reduction in surface oxidation may be detected in Sb 2 Se 3 thin films, and the DC conductivity of the Te-doped Sb 2 Se 3 thin film is in the region of 10 −7 Ω −1 cm −1 at 308.5 K, which is ten times more than the conductivity of pristine Sb 2 Se 3 films that had previously been reported.…”