Effects of Thermochemical Treatment on CuSbS₂ Photovoltaic Absorber Quality and Solar Cell Reproducibility

Abstract

CuSbS2 is a promising nontoxic and earth-abundant photovoltaic absorber that is chemically simpler than the widely studied Cu2ZnSnS4. However, CuSbS2 photovoltaic (PV) devices currently have relatively low efficiency and poor reproducibility, often due to suboptimal material quality and insufficient optoelectronic properties. To address these issues, here we develop a thermochemical treatment (TT) for CuSbS2 thin films, which consists of annealing in Sb2S3 vapor followed by a selective KOH surface chemical etch. The annealed CuSbS2 films show improved structural quality and optoelectronic properties, such as stronger band-edge photoluminescence and longer photoexcited carrier lifetime. These improvements also lead to more reproducible CuSbS2 PV devices, with performance currently limited by a large cliff-type interface band offset with CdS contact. Overall, these results point to the potential avenues to further increase the performance of CuSbS2 thin film solar cell, and the findings can be transferred to other thin film photovoltaic technologies.

High open‐circuit voltage CuSbS2 solar cells achieved through the formation of epitaxial growth of CdS/CuSbS2 hetero‐interface by post‐annealing treatment

“…Figure 2 presents the typical cross‐sectional TEM images of the reference device (named HJRef). No MoS 2 intermediate back layer was observed in our CuSbS 2 solar cells which is consistent with the previous report . This may be due to the relatively low processing temperature (below 400°C) for the absorber, although the formation of MoS 2 is commonly reported in CIGS and CZTS .…”

“…It is widely acknowledged that the low efficiency of CuSbS 2 solar cells mainly arises from both the problematic absorber and unfavourable heterojunction configuration. On the one hand, the low minority carrier lifetime and mobility of the CuSbS 2 absorber lead to a short diffusion length, limiting effective photo‐generated carriers separation and thereby resulting in a low short‐circuit current. On the other hand, the device structure of CuSbS 2 is directly inherited from CIGS counterpart.…”

Selection Metric for Photovoltaic Materials Screening Based on Detailed-Balance Analysis

“…This is not particularly surprising given that our selection of materials generally exhibit quite good optical properties for photovoltaic applications. The current lack of success of materials such as CZTSe [75], CuSbS 2 [76,77] or CuSbSe 2 [78] is a matter of being lower than for Cu(In,Ga)Se 2 . Thus, there is a need for computational materials screening to focus on parameters that are related to the presence of defects such as the search for defect-tolerant materials.…”

Simulation studies on photovoltaic response of ultrathin CuSb(S/Se) 2 ternary compound semiconductors absorber‐based single junction solar cells

“…These results suggest that relatively high back contact work function approximately 5.0 eV is needed to achieve the maximum efficiency for the CuSbS 2 absorber–based devices compared with the CuSbSe 2 absorber, where the maximum efficiency is achieved near approximately 4.7 eV. The formation of a thin Mo(S/Se) 2 layer is less likely during Cusb(S,Se) 2 growth on top of Mo substrate because of relatively lower annealing temperature requirements as compared with CZTS‐based solar devices . However, the presence of Mo(S,Se) 2 cannot be neglected because of the reactivity of S and Se with the Mo bottom layer.…”