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Unrevealing Charge Carrier Selective Layer in Silicon Heterojunction Solar Cells via Multifunctional Atomic Force Probes
摘要： The current silicon solar cell with a record efficiency is based on heterojunction contacts that offer carrier selectivity as well as surface passivation simultaneously. One remaining challenge with heterocontacts is the balance between carrier extraction and surface passivation. Here, it is demonstrated that the heterojunction of n-type silicon (N–Si) with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) removes this trade-off, utilizing the strong depletion of PEDOT:PSS to realize the excellent carrier selectivity. The near-field optical contrast and surface potential distributions of the PEDOT:PSS/N–Si heterojunction via multifunctional atomic force probes are mapped for the first time. Interestingly, a low dielectric value region is observed in N–Si by using scattering-type scanning near-field optical microscopy on the junction cross-section. A special PEDOT:PSS slope is further fabricated to characterize the dielectric value and surface potential in the PEDOT:PSS side. By combining s-SNOM and scanning Kelvin probe microscopy, a special region in PEDOT:PSS is observed with a sharp surface potential drop and low dielectric value. The results suggest the existence of space charge regions both in N–Si and PEDOT:PSS at the interface. These findings contribute the understanding of the physical properties of the silicon heterojunction and promise potential routes to enhance device efficiency.
关键词： poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate)/n-type silicon interface,scanning Kelvin probe microscopy,carrier redistribution,infrared scattering-type scanning near-field optical microscope
更新于2025-09-11 14:15:04
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Insights into the excited state dynamical process for 3-hydroxy-2-(5-(5-(5-(3-hydroxy-4-oxo-4H-chromen-2-yl)thiophen-2-yl)thiophen-2-yl)thiophen-2-yl)-4H-chromen-4-one
摘要： In this present work, we theoretically investigate a novel system 3‐hydroxy‐2‐(5‐(5‐(5‐(3‐hydroxy‐4‐oxo‐4H‐chromen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)‐4H‐chromen‐4‐one (FT) based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. Via calculating the reduced density gradient (RDG) versus sign(λ2) ρ, we firstly verify the formation of the dual intramolecular hydrogen bonds (O1─H2···O3 and O4─H5···O6) for FT form in the S0 state. Then comparing the primary structural parameters and corresponding infrared (IR) vibrational spectra involved in hydrogen bonds between S0 and S1 state, we demonstrate that these two intramolecular hydrogen bonds should be strengthened in the S1 state. Insights into the vertical excitation process, our theoretical results reproduced experimental absorption nature, which confirms that the theoretical level (B3LYP/TZVP) is reasonable and effective in this work. And frontier molecular orbitals (MOs) depict the nature of electronically excited state and support the excited‐state intramolecular proton transfer (ESIPT) reaction. According to the calculated results of potential energy curves along stepwise and synergetic O1─H2 and O4─H5 coordinates, we verify that only the excited‐state single‐proton transfer could occur for FT molecule in the S1 state, although it possesses two intramolecular hydrogen bonds. We not only investigate the detail excited‐state behaviors for FT system and elaborate the ESIPT mechanism but also explain previous experimental results.
关键词： charge redistribution,ESIPT,intramolecular hydrogen bond,charge density difference
更新于2025-09-04 15:30:14