Enhanced efficiency and stability in indoor organic photovoltaics with spray-deposited, liquid-processable MoS₂ and WS₂ hole transport layers

Liquid-phase exfoliated molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) nanosheets were developed as efficient and scalable hole transport layers (HTLs) for organic photovoltaic (OPV) devices. Few-layer WS₂ and MoS₂ were successfully exfoliated via ultrasonication and incorporated into OPVs using spray-deposition. Comprehensive characterization confirmed the high purity and nanoscale integrity of the exfoliated materials. OPVs with WS₂ and MoS₂ HTLs achieved superior performance under both standard AM 1.5G and indoor (LED 1000 lx) illumination. WS₂-based devices demonstrated the highest power conversion efficiencies (PCEs) of 15.6% (AM 1.5G) and 31.6% (LED 1000 lx), while MoS₂-based devices reached 15.1% and 29.7%, respectively, outperforming PEDOT:PSS-based devices (14.9% and 24.9%). These improvements were linked to enhanced charge transport and reduced recombination losses enabled by the TMD-based HTLs. Stability testing showed that MoS₂-based devices retained 85% of their initial PCE after 1000 h under ambient conditions, compared to 80% for WS₂ and 55% for PEDOT:PSS. AFM analysis revealed that TMD HTLs created smoother active layer surfaces, reducing recombination sites and boosting efficiency. This work highlights the potential of WS₂ and MoS₂ as high-performance, stable, and scalable HTLs, offering significant advantages over PEDOT:PSS for both outdoor and indoor OPV applications.