Numerical Investigation of Interface Passivation Strategies for Sb₂Se₃/CdS Solar Cells

Abstract

Sb2Se3 is an emerging earth‐abundant material praised for its promising optoelectronic properties, although the presence of interfacial defects at the vicinity of the p–n junction limit its performance as photovoltaic absorber. Using a device modeling approach and a realistic set of material parameters, it unravels pathways mitigating the impact of interfacial defects with a baseline Sb2Se3/CdS. Two straightforward strategies are devised and tested against the baseline. First, a thin front surface sulfurization of the Sb2Se3 absorber allowing a local lowering of the valence band and creating a “front surface field,” resulting in an increased carrier selectivity and limiting the density of holes available for interface recombination, leading to a significant efficiency improvement for optimized conditions. Second, the use of an ultrathin insulating Al2O3 layer between the absorber and the buffer layer is considered, helping in preventing detrimental chemical interdiffusion at the junction. This strategy provides a direct interface passivation, though the interlayer thickness needs a fine tuning to balance the benefits of reduced interface recombination and a detrimental Al2O3 low‐conductivity layer. In each case, an analysis covering a broad range of parameters is presented, and conclusions are made in the frame of past numerical and experimental results.

KCN Chemical Etching of van der Waals Sb2Se3 Thin Films Synthesized at Low Temperature Leads to Inverted Surface Polarity and Improved Solar Cell Efficiency

“…To test the hypothesis of a buried homojunction following KCN etching, we conducted numerical simulations investigating the influence of an ultrathin n-doped layer on the surface of the absorber in a SCAPS-1D model, building upon the previously reported baseline that simulates the behavior of Sb 2 Se 3 . 18 We varied the doping level of the n-type surface layer from 10 13 to 10 19 cm –3 and the doping depth from 2 to 20 nm, while keeping other parameters constant, including the interface defect properties. As the exact characteristics of this doping layer are currently unknown, we performed a parametric variation of both doping level and depth simultaneously to create surface plots for each photovoltaic figure of merit.…”

“…This was experimentally confirmed by Mao et al in superstrate configuration Sb 2 (S,Se) 3 solar cells. Gon Medaille et al also demonstrate that either selective surface sulfurization or the introduction of a very thin Al 2 O 3 layer at the interface could also significantly reduce the interface recombination, boosting the efficiency of the devices . Experimentally, Feng et al reported an efficiency enhancement by adding an ultrathin (between 0.1 and 2 nm) Si 3 N 4 passivating layer between the absorber and the CdS layer in substrate configuration devices .…”

“…Although Sb 2 Se 3 has clear advantages over other materials and is composed of only two elements, secondary phases, bulk recombination centers, and interfacial defects are still expected to occur . According to previously reported simulations, and considering the current state-of-the-art methods, interfacial defects are the most detrimental in terms of the solar cells efficiency degradation, affecting especially the open-circuit voltage ( V OC ) of the devices. , In this regard, theoretical studies reported by Chen et al suggest that the introduction of an ultrathin SnO 2 layer is beneficial for the passivation of the interfacial defects of Sb 2 Se 3 .…”

“…Gon Medaille et al also demonstrate that either selective surface sulfurization or the introduction of a very thin Al 2 O 3 layer at the interface could also significantly reduce the interface recombination, boosting the efficiency of the devices. 18 Experimentally, Feng et al reported an efficiency enhancement by adding an ultrathin (between 0.1 and 2 nm) Si 3 N 4 passivating layer between the absorber and the CdS layer in substrate configuration devices. 21 In addition, Prabhakar et al observed a passivation effect of selective surface sulfurization, although these materials were investigated for water splitting applications.…”

Reactive DC Sputtered TiO2Electron Transport Layers for Cadmium‐Free Sb2Se3Solar Cells

“…Given the variable J-V distortion observed in the present study, our previous work, and seemingly elsewhere in Sb 2 Se 3 literature with TiO 2 ETLs, a model of our device was constructed to allow for interrogation of the underlying device physics. The baseline Sb 2 Se 3 device model is adapted from Medaille et al, [92] which was defined using experimental data, and is detailed in Tables S4-S6 (Supporting Information).…”