Exploring Cs2AgBiBr6 halide double perovskite as a lead-free emissive material for perovskite LEDs Kamal Kumar Jain, Sarita Yadav, Saral K Gupta, C M S Negi Physica Scripta, 2025 Numerical simulations were performed to evaluate the suitability of cesium silver bismuth bromide (Cs 2 AgBiBr 6 ) halide double perovskite as an efficient emissive layer (EML) for perovskite-based LEDs (PeLEDs). The study investigates various hole-injection layer (HIL) materials, revealing their substantial impact on device performance. Hole mobility and energy barriers at the metal/HIL and HIL/EML interfaces are identified as key determinants of optoelectronic efficiency. Among the tested HILs, Cu 2 O delivered the best performance, achieving a maximum EQE of 27.36% and current efficiency (CE) of 51.84 cd A −1 , followed by NiO (EQE: 9.81%, CE: 47.32 cd A −1 ) and CBTS (EQE: 1.14%, CE: 3.96 cd A −1 ), owing to its high hole mobility and balanced carrier injection. HIL thickness was found to have negligible influence on PeLEDs characteristics. Doping-dependent analysis shows that PeLEDs performance declines gradually with acceptor concentration up to 10 18 cm −3 but deteriorates sharply beyond this point, while donor doping enhances performance up to 10 19 cm −3 before Auger recombination becomes dominant. These trends are mainly ascribed to shifts in the recombination zone with doping variation. Additionally, increasing defect density markedly reduces luminance and current efficiency due to enhanced Shockley–Read–Hall (SRH) recombination, which lowers IQE and EQE by promoting non-radiative pathways over radiative recombination. This work provides valuable insights to strengthen research efforts on Pb-free PeLEDs in the field of environmentally friendly optoelectronics.
Synergistic effects of N719 and N3 dyes in DSSCs with gel polymer electrolyte and graphite counter electrode Ritu, Saral Kumar Gupta, C.M.S. Negi Next Materials, 2025 Dye-sensitized solar cells (DSSCs) offer a low-cost and eco-friendly alternative for next-generation photovoltaics, but their efficiency is often limited by the choice of dyes, electrolytes, and counter electrodes. In this work, we demonstrate the synergistic impact of co-sensitization with N719 and N3 dyes on the photovoltaic performance of DSSCs. Unlike conventional DSSCs employing platinum as the counter electrode and liquid electrolytes, pencil graphite was utilized here as a cost-effective and sustainable counter electrode, while a PVDF-HFP-based gel polymer electrolyte prepared via the solution-casting method was employed as the quasi-solid-state electrolyte. UV-Vis absorption spectroscopy revealed broadened and red-shifted absorption for the co-sensitized system, indicating enhanced light harvesting. Furthermore, the co-sensitized dye/TiO 2 film exhibited reduced energetic disorder and a lower density of localized tail states, as evidenced by its lowest Urbach energy. FESEM and EDX confirmed uniform dye loading and improved surface coverage, while Raman spectroscopy indicated stable dye–TiO 2 interactions. Photovoltaic measurements showed that the co-sensitized DSSC achieved the highest PCE of 5.82 %, outperforming single-dye devices (N3: 4.19 %, N719: 3.83 %) due to synergistic spectral coverage, improved electron injection, and suppressed recombination. Electrochemical impedance spectroscopy further corroborated these findings by revealing reduced charge-transfer resistance and improved ionic diffusion in the co-sensitized device. These results demonstrate that combining co-sensitization with a quasi-solid-state electrolyte and a low-cost graphite counter electrode provides an effective pathway toward affordable and sustainable DSSCs • A low-cost, quasi-solid-state DSSC, with pencil graphite CE was developed. • Co-sensitization with N719 and N3 dyes significantly enhanced light harvesting. • The co-sensitized DSSC exhibited the highest PCE (5.82 %). • EIS analysis corelated well with the photovoltaic performance of the DSSCs.
Role of annealing conditions on the resistive switching behavior of solution processed formamidinium lead bromide FaPbBr3 devices Amrita Singh, Saumya Paliwal, Aditi Upadhyaya, Saral Kumar Gupta, C.M.S. Negi Nano Trends, 2025 Hybrid organic-inorganic halide perovskites (OIHPs) are emerging as strong contenders for next-generation flexible nonvolatile memory systems due to their fascinating properties, including mixed ionic-electronic transport, high abundance, and cost-effective fabrication processes. This study investigates the impact of annealing the active layer on the resistive switching (RS) performance of FTO/formamidinium lead bromide (FAPbBr 3 )/Al devices. Devices were fabricated with the FAPbBr 3 layer annealed under different conditions: 50 °C for 10 min (Device D1), 60 °C for 20 min (Device D2), and 100 °C for 30 min (Device D3). Each device displayed distinct bipolar hysteresis in current-voltage (I-V) characteristics, with Device D2 displaying the most prominent hysteresis loop. X-ray diffraction (XRD) analysis identified that the FAPbBr 3 layer in Device D2 predominantly contained the FABr–PbBr 2 –DMF intermediate complex, resulting in a higher density of native defects. This increased defect density likely enhanced bromide ion migration, facilitating greater ionic accumulation at the interface, which contributed to the pronounced hysteresis loop. A model combining ionic transport and energy band modulation is proposed to elucidate the resistive switching (RS) mechanism in these devices. Capacitance-frequency (C–f) analysis further corroborated the highest interfacial charge accumulation for Device D2, reflected by its maximum accumulation capacitance. Additionally, the Device D2 exhibited the highest ionic conductivity, driving enhanced ion migration and accumulation at the interface, thereby enhancing the RS behavior. This work highlights the critical role of annealing in optimizing the RS performance, offering valuable insights for advancing perovskite-based RS device technologies.
Investigating charge injection, transport, and electronic performance in rGO-integrated TIPS pentacene blend devices Saumya Paliwal, Amrita Singh, Aditi Upadhyaya, Saral Kumar Gupta, C M S Negi Physica Scripta, 2025 This study demonstrates the successful integration of reduced graphene oxide (rGO) into the TIPS pentacene framework, leading to significant enhancements in device performance. The fabricated devices exhibit ideality factors ranging from 2.1 to 2.6, indicating that trap-assisted Shockley Read Hall (SRH) recombination dominates the charge recombination mechanism. The Schottky barrier height (SBH) values, estimated using both the Richardson-Schottky (RS) thermionic emission model and an alternative calculation method, show excellent consistency, confirming the reliability of both approaches. Leakage current is primarily dictated by a direct tunnelling mechanism, while charge conduction is well-explained by the space-charge-limited current (SCLC) model. Optimal device performance, characterized by peak hole mobility and shortest rise times, is achieved with 3% rGO concentration, highlighting its potential for high-speed switching applications. Capacitance-frequency (C–f) analysis reveals a slight frequency dependence at lower frequencies, attributed to charge traps, while the dielectric constants obtained from C–f measurements align with those derived from the RS thermionic emission model. These findings demonstrate the suitability of rGO-doped TIPS pentacene for advanced electronic devices, particularly in high-speed applications.
Ab initio studies of structural, electronic, optical, elastic and thermal properties of copper thallium dichalcogenides (CuTiX2: X=S, Se, Te) Chalcogenide Letters, 2019
