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Deep insights into interface engineering by buffer layer for efficient perovskite solar cells: a first-principles study; é?????é??é??????¤aé?3è????μ?±???-?????2?±????é?￠?·￥?¨?????·±??￥???è§￡: ????????§????????????;
摘要： Recent years have seen swift increase in the power conversion efficiency of perovskite solar cells (PSCs). Interface engineering is a promising route for further improving the performance of PSCs. Here we perform first-principles calculations to explore the effect of four candidate buffer materials (MACl, MAI, PbCl2 and PbI2) on the electronic structures of the interface between MAPbI3 absorber and TiO2. We find that MAX (X = Cl, I) as buffer layers will introduce a high electron barrier and enhance the electron-hole recombination. Additionally, MAX does not passivate the surface states well. The conduction band minimum of PbI2 is much lower than that of MAPbI3 absorber, which significantly limits the band bending of the absorber and open-circuit voltage of solar cells. On the other side, suitable bandedge energy level positions, small lattice mismatch with TiO2 surfaces, and excellent surface passivation make PbCl2 a promising buffer material for absorber/electron-transport-layer interface engineering in PSCs. Our results in this work thus provide deep understanding on the effects of interface engineering with a buffer layer, which shall be useful for improving the performance of PSCs and related optoelectronics.
关键词： perovskite solar cells,band alignment,interfacial defect passivation,buffer layer,interface engineering
更新于2025-09-23 15:21:01
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Novel cathode buffer layer of Al(acac)3 enables efficient, large area and stable semi-transparent organic solar cells
摘要： Electrode buffer layer plays a more crucial in semi-transparent organic solar cells (ST-OSCs) than that of the opaque devices due to the additional requirements of the average visible transmittance (AVT) and color rendering index (CRI) besides the power conversion efficiency (PCE). Herein, we developed a novel cathode buffer layer Aluminum(III) acetylacetonate (Al(acac)3) via mild spin-coating with post low temperature heat treatment process. Studies show that Al(acac)3 film possess outstanding optical features and suitable energy level. Namely, the absorption of Al(acac)3 film with thickness of 10 nm is as low as 1% and the transmittance is high up to 95% in the visible and near infrared regions, guarantying full absorption of the photoactive layer and high CRI for ST-OSCs; and the suitable energy level ensures a smooth electron transport and collection process. By introducing Al(acac)3 film in ST-OSCs, the devices based on PM6:Y6 yield an efficiency of 12.41%, an AVT of 25.33% (from 370 nm to 740 nm) and a CRI of 94.6. Encouragingly, the large-area ST-OSC of 100 mm2 with Al(acac)3 buffer layer yields an efficiency of 11.28%. Further long-term stability of ST-OSCs show that the device with encapsulation retains its 60% of the initial PCE over 60 hours continuous illumination. The results indicate that Al(acac)3 is a promising cathode buffer layer for fabricating efficient, large area and stable semi-transparent organic solar cells.
关键词： Semitransparent organic solar cells,cathode buffer layer,stability,Aluminum(III) acetylacetonate,large-area device
更新于2025-09-23 15:21:01
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Improved Interface Contact for Highly Stable All-Inorganic CsPbI2Br Planar perovskite solar cells
摘要： Owing to its suitable bandgap and remarkable thermal stability, all-inorganic perovskite CsPbI2Br has caught the eye of the academic research and industry recently. However, it still suffers from a phase transition due to poor stability at ambient atmosphere. Here, we introduce CsBr as an interfacial layer between the electron transport layer and the CsPbI2Br perovskite absorber layer to induce a more favorable perovskite crystal growth and fabricated devices with a facile structure of (ITO/SnO2/CsBr/CsPbI2Br/Spiro-OMeTAD/Ag). The CsBr buffer layer plays a role in reducing the lattice mismatch so that it cannot only induce and manage the formation of CsPbI2Br film but also significantly enhance the phase stability of the perovskite. After the modification, the devices reveal conspicuous improvement in illuminated, thermal, ambient, and long-term stabilities without any encapsulation. Meanwhile, the device performance is also improved. The unencapsulated CsBr treated device manifests illuminated stability with PCE remaining almost above 80 % of its initial value after long-time exposure, the remarkable thermal stability of remaining over 78 % of the initial values, better humid resistance, and only 13% decline after being stored in N2 glove-box over 40 days.
关键词： interface contact,CsPbI2Br,stability,passivation,buffer layer
更新于2025-09-23 15:21:01
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Double fullerene cathode buffer layers afford highly efficient and stable inverted planar perovskite solar cells
摘要： Fullerene derivatives especially [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) with strong electron-accepting abilities have been commonly implemented as indispensable cathode buffer layers (CBLs) of inverted (p-i-n) planar perovskite solar cells (iPSCs) to facilitate electron transport. However, only a single fullerene CBL is typically used in iPSC devices, resulting in interfacial energy offset between fullerene CBL and metal cathode and consequently insufficient electron transport. Herein, we synthesized a novel bis-dimethylamino-functionalized fullerene derivative (abbreviated as PCBDMAM) and applied it as an auxiliary fullerene interlayer atop of PCBM to form a PCBM/PCBDMAM double fullerene CBL, leading to dramatic enhancement of both efficiency and ambient stability of iPSC devices. Incorporation of PCBDMAM interlayer facilitates the formation of interfacial dipole layer between PCBM and Ag cathode, resulting in decrease of the work function of the Ag cathode. As a result, the CH3NH3PbI3 (MAPbI3) iPSC devices based on PCBM/PCBDMAM double fullerene CBL exhibit the highest power conversion efficiency (PCE) of 18.11%, which is drastically higher than that of the control device based on single PCBM CBL (14.21%) and represents the highest value reported for double fullerene CBL-based iPSC devices. Moreover, due to the higher hydrophobicity of PCBDMAM than PCBM, iPSC devices based on PCBM/PCBDMAM double fullerene CBL shows an enhanced ambient stability, retaining 67% of the initial PCE after storage 1440 h exposure under the ambient atmosphere without any encapsulation, whereas only 43% retaining was achieved for the control device based on single PCBM CBL.
关键词： Cathode buffer layer,Perovskite solar cells,Work function,Interfacial engineering,Fullerene derivative
更新于2025-09-23 15:21:01
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Hybrid chemical bath deposition-CdS/sputter-Zn(O,S) alternative buffer for Cu <sub/>2</sub> ZnSn(S,Se) <sub/>4</sub> based solar cells
摘要： To replace the conventionally used CdS buffers in Cu2ZnSn(S,Se)4 (CZTSSe) based thin-film solar cells, sputtered Zn(O,S) buffer layers have been investigated. Zn(O,S) layers with three different [O]/([O] + [S]) ratios (0.4, 0.7, and 0.8)—and a combination of Zn(O,S) and CdS (“hybrid buffer layer”) were studied. In comparison to the CdS reference, the external quantum efficiency (EQE) of the Zn(O,S)-buffered devices increases in the short- and long-wavelength regions of the spectrum. However, the average EQE ranges below that of the CdS reference, and the devices show a low open-circuit voltage (VOC). By adding a very thin CdS layer (5 nm) between the absorber and the Zn(O,S) buffer, the VOC loss is completely avoided. Using thicker intermediate CdS layers result in a further device improvement, with VOC values above those of the CdS reference. X-ray photoelectron spectroscopy (XPS) measurements suggest that the thin CdS layer prevents damage to the absorber surface during the sputter deposition of the Zn(O,S) buffer. With the hybrid buffer configuration, a record VOC deficit, i.e., a minimum difference between bandgap energy Eg (divided by the elementary charge q) and VOC (Eg/q – VOC) of 519 mV could be obtained, i.e., the lowest value reported for kesterite solar cells to date. Thus, the hybrid buffer configuration is a promising approach to overcome one of the main bottlenecks of kesterite-based solar cells, while simultaneously also reducing the amount of cadmium needed in the device.
关键词： VOC deficit,Cu2ZnSn(S,Se)4,CdS,hybrid buffer layer,open-circuit voltage,X-ray photoelectron spectroscopy,thin-film solar cells,Zn(O,S) buffer layers,external quantum efficiency
更新于2025-09-23 15:19:57
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Buffer layers inhomogeneity and coupling with epitaxial graphene unravelled by Raman scattering and graphene peeling
摘要： The so-called buffer layer (BL) is a carbon rich reconstructed layer formed during SiC (0001) sublimation. The covalent bonds between some carbon atoms in this layer and underlying silicon atoms makes it different from epitaxial graphene. We report a systematical and statistical investigation of the BL signature and its coupling with epitaxial graphene by Raman spectroscopy. Three different BLs are studied: bare buffer layer obtained by direct growth (BL0), interfacial buffer layer between graphene and SiC (c-BL1) and the interfacial buffer layer without graphene above (u-BL1). To obtain the latter, we develop a mechanical exfoliation of graphene by removing an epoxy-based resin or nickel layer. The BLs are ordered-like on the whole BL growth temperature range. BL0 Raman signature may vary from sample to sample but forms patches on the same terrace. u-BL1 share similar properties with BL0, albeit with more variability. These BLs have a strikingly larger overall intensity than BL with graphene on top. The signal high frequency side onset upshifts upon graphene coverage, unexplainable by a simple strain effect. Two fine peaks (1235, 1360 cm-1), present for epitaxial monolayer and absent for BL and transferred graphene. These findings point to a coupling between graphene and BL.
关键词： Buffer layer,Mechanical peeling,Graphene,Raman spectroscopy
更新于2025-09-23 15:19:57
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Effect of insertion of bathocuproine buffer layer at grating-structured cathodea??organic-layer interface in bulk-heterojunction solar cells
摘要： A grating-structured interface of a poly(3-hexylthiophene) (P3HT) and n-type [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)-based bulk-heterojunction (BHJ) photovoltaic (PV) cell was designed and fabricated to obtain a desirable thickness distribution of the deposited bathocuproine (BCP) buffer layer to efficiently utilize its potentials. As a master mold of the grating-structure, a commercially available recordable digital versatile disc (DVD-R) substrate was employed. The grating-structured surface of the P3HT:PCBM layer was successfully produced by duplication from a poly(dimethylsiloxane) secondary mold using the spin cast molding technique. From morphological observations of the grating-structured surface covered with vapor-deposited BCP, we roughly estimated the ratio of the BCP thickness at “walls” to that at “top” and “bottom” regions to be ～0.5. The grating-type BHJ PV cell with a 5-nm-thick BCP layer exhibited the maximum power-conversion efficiency (ηp) of 3.51%. Compared with the conventional flat-type BHJ PV cell with a 20-nm-thick BCP layer, the performance of the grating-type BHJ PV cell with a 20-nm-thick BCP layer was remarkably improved, owing to the contribution of the wall side contact, which provides a lower-barrier path of the electrons toward the cathode through the thinner BCP layer.
关键词： bathocuproine buffer layer,grating-structured interface,bulk-heterojunction solar cells,power-conversion efficiency
更新于2025-09-23 15:19:57
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Surface-enhanced Raman scattering from buffer layer under graphene on SiC in a wide energy range from visible to near-infrared
摘要： Raman signals from the buffer layer between graphene and a SiC substrate are enhanced through the formation of nano-structured Au deposited directly on graphene grown on SiC. This simple method makes it possible to deconvolute multiple graphene and buffer layer peaks in a wide energy range from 1.58 to 2.33 eV and find new buffer layer peaks that are not resolved in conventional Raman scattering spectroscopy. Furthermore, we clearly show a small linear excitation energy dependence for one of the buffer layer peak positions and an absence of energy dependence for the peaks at most of the other positions.
关键词： buffer layer,Surface-enhanced Raman scattering,graphene,SiC,near-infrared
更新于2025-09-23 15:19:57
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Interface Engineering Assisted 3D-Graphene/Germanium Heterojunction for High-Performance Photodetectors
摘要： Three-dimensional graphene (3D-Gr) with excellent light absorption properties has received enormous interest but in conventional processes to prepare 3D-Gr, amorphous carbon layers are inevitably introduced as buffer layers which may degrade the performance of graphene-based devices. Herein, 3D-Gr is prepared on germanium (Ge) using two-dimensional graphene (2D-Gr) as the buffer layer. 2D-Gr as the buffer layer facilitates in-situ synthesis of 3D-Gr on Ge by plasma-enhanced chemical vapor deposition (PECVD) by promoting 2D-Gr nucleation and reducing the barrier height. The growth mechanism is investigated and described. The enhanced light absorption as confirmed by theoretical calculation and 3D-Gr/2D-Gr/Ge with a Schottky junction improves the performance of optoelectronic devices without requiring pre- and post-transfer processes. The photodetector constructed with 3D-Gr/2D-Gr/Ge shows an excellent responsivity of 1.7 AW-1 and detectivity 3.42 × 1014 cmHz1/2W?1 at a wavelength of 1,550 nm. This novel hybrid structure which incorporates 3D- and 2D-Gr into Ge-based integrated circuits and photodetectors deliver excellent performance and has large commercial potential.
关键词： Buffer layer,Germanium,Photodetectors,Built-in potential,3D/2D-graphene
更新于2025-09-23 15:19:57
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Comparative studies of CdS thin films by chemical bath deposition techniques as a buffer layer for solar cell applications
摘要： Cadmium sulfide (CdS) buffer layer that decouples the absorber layer and window layer in thin-film solar cells was synthesized by two different chemical bath deposition (CBD) techniques with varying deposition parameters. X-ray diffraction (XRD) revealed that the CdS thin film crystallizes in a stable hexagonal wurtzite structure having a preferential orientation along (002) reflection plane with a crystallite size varying from 20 to 40 nm. First longitudinal optical phonon mode was identified at Raman shift of 305 cm?1. Uniform, granular, continuous, and smooth surface with an average grain sizes (< 100 nm) as well as small roughness (< 9 nm) was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. The symmetric composition of cadmium and sulfur along with larger grains (20 nm) was observed at higher deposition temperatures and times. The optical band gap of CdS samples obtained from process one was in the range of 2.3–2.35 eV, while the band gap by the second CBD process lay in between 2.49 and 2.65 eV, showing the most stable compound of CdS. The presence of a green emission band in photoluminescence spectra (PL) demonstrated that the CdS material has better crystallinity with minimum defect density. Hall effect studies revealed the n-type conductivity of CdS thin films with a carrier concentration values in the order of 1016 cm?3. Furthermore, CdS thin films fabricated by CBD process exposed better quality that might be more suitable material as a buffer layer for thin-film solar cells.
关键词： solar cells,buffer layer,optical properties,electrical properties,chemical bath deposition,CdS thin films
更新于2025-09-23 15:19:57