Crystallographic Orientation Control of 1D Sb₂Se₃ Nanorod Arrays for Photovoltaic Application by In Situ Back‐Contact Engineering

Abstract

Low‐dimensional (LD) crystalline inorganic semiconductors have attracted increasing interest due to their unique electrical and optical properties. The crystallographic orientation in the LD films is one of the critical parameters that determine their strong anisotropic physical properties and device performance. Antimony selenide (Sb2Se3), a 1D crystalline semiconductor, is a promising absorber material for emerging photovoltaic technologies. The suitably oriented Sb2Se3 absorbers can offer excellent carrier transport and trap‐free grain boundaries, facilitating high‐efficiency devices. The crystallographic orientation of the Sb2Se3 light‐absorbing layer is found to be governed by the underlying layers, i.e., the back contact in substrate‐type solar cells. Herein, an in situ surface selenization treatment to the tungsten (W) back contact is applied to change the growth of Sb2Se3 layer from a layer‐like growth mode to an island‐like growth mode. As a result, highly [hk1]‐oriented Sb2Se3 nanorod arrays growing perpendicular to the W back‐contact surface are achieved. Moreover, the resulting tungsten selenide (WSe2) thin layer also acts as a hole transport layer and promotes hole extraction. Consequently, a conversion efficiency as high as 8.46% in Sb2Se3 solar cells with substrate configuration is achieved.

Boosting VOC of antimony chalcogenide solar cells: A review on interfaces and defects

“…Recently, Liang et al deposited a WSe 2 layer on W film by in-situ selenization engineering. [140] They found that Sb 2 Se 3 film grown on top of WSe 2 films was dominated by [221] orientation, while a [120]-preferred orientation dominated in Sb 2 Se 3 film grown on as-deposited W, which is suggested to be attributed to the formation of the thin WSe 2 inter-facial layer during the in-situ selenization process. As a result, the best device efficiency reached 8.46% with a significantly increased V OC of 402 mV.…”

“…Reproduced with permission. [ 140 ] Copyright 2020, Wiley‐VCH. F, DLTS signals of devices with 2.21% Te and 5.32% S doping.…”

Band versus Polaron: Charge Transport in Antimony Chalcogenides

“…70 Despite the anisotropic behavior, even at moderate defect concentrations, the electron and hole mobilities are still reasonably large (>10 cm 2 V −1 s −1 ) in at least two directions. The common description of Sb 2 X 3 as a 1D semiconductor 71,72 oversimplifies the nature of transport. Accordingly, it may be possible to obtain high-mobility thin films, even when the grains are not fully aligned along the direction of the quasi-1D ribbons.…”

HTL-Free Sb2(S, Se)3 Solar Cells with an Optimal Detailed Balance Band Gap

“…Owing to the similar orthorhombic crystal structures ( Pnma 62) of Sb 2 Se 3 and Sb 2 S 3 , the band gap of Sb 2 (S, Se) 3 can be continuously tuned in the range from 1.1 to 1.7 eV by changing the Se/S ratio (Figure ). − Thus, an Sb 2 (S, Se) 3 solar cell with a desired band gap of ∼1.3 eV is feasible to obtain higher PCE.…”