Akademik Veri Yönetim Sistemi
Journal of Materials Science: Materials in Electronics, cilt.37, sa.2, 2026 (SCI-Expanded, Scopus)
The low conductivity of nickel oxide hole transporters is the main disadvantage to getting superior power conversion efficiencies for planar p-i-n type perovskite solar cells. This study aims to enhance the conductivity of conventional nickel oxide layers by incorporating graphene additives. Graphene nanoplatelets (GNP) and Thermally Exfoliated Graphene Oxide (TEGO) were directly introduced to the nickel oxide layer in the step of precursor preparation. Entire solar cell fabrication with a configuration of ITO/NiOx/CH3NH3PbI3/PCBM/BCP/Ag was conducted in ambient air through sol–gel processes without a glove box. Results revealed increased short-circuit current densities and open-circuit voltages with the graphene additives, and TEGO performed slightly better than GNP, giving a ~ 15% increase in power conversion efficiencies. This enhancement was scrutinized and confirmed through a series of experiments, including X-ray diffraction, UV–visible spectrophotometry, field-emission scanning electron microscopy, Kelvin Probe microscopy, and electrical measurements. Graphene additives were found to increase the work function from 5.18 eV to 5.21 eV. Hence, combined with increased electrical conductivity, one can conclude a clear increment in charge extraction with a lowered recombination loss, which suggests solar cell performance. The conductivity of NiOx increased by 57.0% and 103.7% for GNP- and TEGO-modified films, respectively, while the work function slightly increased by 0.58% (GNP) and 0.39% (TEGO). XRD and FESEM analyses confirmed enlarged perovskite grain sizes, particularly in the GNP-based devices. These improvements resulted in enhanced device performance: the average short-circuit current density increased from 18.0 mA/cm2 to 22.7 mA/cm2 (GNP) and 22.1 mA/cm2 (TEGO), open-circuit voltages increased from 1018 to 1034 mV (GNP) and 1036 mV (TEGO), and the fill factor increased from 62.1% to 64.6% (GNP) and 65.5% (TEGO). Consequently, the average PCE increased from 11.6% to 15.2% (GNP) and 15.0% (TEGO), with champion open-circuit voltage values reaching 1082 mV. The hysteresis factor was also greatly reduced to 0.012 (GNP) and 0.018 (TEGO), compared to 0.13 for pristine NiOx. Long-term stability tests demonstrated that after 96 h, TEGO- and GNP-modified devices retained 98% and 96% of their initial PCE, while the reference dropped to 76%. After 350 h, GNP and TEGO retained 95% and 81%, respectively, while the reference fell to 62%. These trends correlate with lower VTFL values from SCLC curves, indicating reduced trap densities, calculated as 3.38 1016 cm−3, 3.40 1016 cm−3, and 3.81 1016 cm−3 for GNP, TEGO, and reference HTL, respectively, employed hole-only devices, respectively.