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Role of Molecular and Interchain Ordering in the Formation of a δ-Hole Transporting Layer in Organic Solar Cells
摘要： Interface engineering, especially the realisation of ohmic contacts at the interface between organic semiconductors and metal contacts, is one of the essential preconditions to achieve high efficiency organic electronic devices. Here, the interface structure of polymer/fullerene blends are correlated with the charge extraction/injection properties of working organic solar cells. The model system – P3HT:PCBM – is fabricated using two different degrees of P3HT regioregularity to alter the blend interchain order and molecular packing, resulting in different device performance. Investigations by electroabsorption (EA) spectroscopy on these devices indicate a significant reduction (≈ 1 V) in the built-in potential with an increase in the P3HT regioregularity. This observation is also supported by a change in the WF of high regioregular polymer blends from photoelectron spectroscopy measurement. These results confirm the presence of a strong dipole layer acting as a δ-hole transporting layer at the polymer/MoO3/Ag electrode interface. Unipolar hole-only devices show an increase in the magnitude of the hole current in high regioregular P3HT devices, suggesting an increase in the hole injection/extraction efficiency inside device with a δ-hole transporting layer. Microscopically, near edge X-ray absorption fine structure (NEXAFS) spectroscopy was conducted to probe the surface microstructure in these blends finding a highly edge-on orientation of P3HT chains in blends made with high regioregular P3HT. This edge-on orientation of P3HT chains at the interface results in a layer of oriented alkyl side chains capping the surface which favors the formation of a dipole layer at the polymer/MoO3 interface. The increase in the charge extraction efficiency due to the formation of a δ-hole transporting layer thus results in higher short circuit currents and fill factor values, eventually increasing the device efficiency in high regioregular P3HT devices despite a slight decrease in cell open circuit voltage. These findings emphasise the significance of work function control as a tool for improved device performance, and pave the way towards interfacial optimisation based on the modulation of fundamental polymer properties, such as polymer regioregularity.
关键词： Organic solar cells,interface engineering,molecular ordering,regioregularity,interface dipole,interchain ordering,P3HT
更新于2025-09-12 10:27:22
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Facile Formation of 2D-3D Heterojunctions on Perovskite Thin Film Surfaces for Efficient Solar Cells
摘要： The interfaces between perovskite and charge transport layers greatly impact the device efficiency and stability of perovskite solar cells (PSCs). Inserting an ultrathin wide bandgap layer between perovskite and hole transport layers (HTL) has recently been shown as an effective strategy to enhance device performance. Herein, a small amount of organic halide salt, N,N’-dimethylethylene-1,2-diammonium iodide, is used to create 2D-3D heterojunctions on MAPbI3 thin film surfaces by facile solution processing. The formation of ultrathin wide bandgap 2D perovskite layer on top of 3D MAPbI3 changes the morphological and photophysical properties of perovskite thin films, effectively reduces the surface defects, and suppresses the charge recombination in the interfaces between perovskite and HTL. As a result, a power conversion efficiency of ~ 20.2%, with an open circuit voltage of 1.14 V, a short-circuit current density of 22.57 mA cm-2, and a fill factor of 0.78, is achieved for PSCs with enhanced stability.
关键词： Perovskite solar cells,2D-3D heterojunctions,interface engineering,stability,surface passivation
更新于2025-09-12 10:27:22
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Tailored interfacial crystal facets for efficient CH3NH3PbI3 perovskite solar cells
摘要： Interface engineering is generally requisite for highly efficient perovskite solar cells (PSCs). However, the current interface engineering methods inevitably introduce extra modifier layers into PSCs, which not only complex the configurations and fabrication procedures, but also increase the production cost of PSCs. Herein, we propose an interface engineering strategy for PSCs by controlling the nature of Lead halide perovskite films, and specifically their interfacial grain facets. In detail, a solution-mediated secondary growth (SSG) technology is demonstrated to tailor interfacial grain facets in CH3NH3PbI3 PSC. The precise tailoring ability of interfacial grain facets is achieved by controlling SSG temperature. When it is optimized to 60 °C, interfacial grains of CH3NH3PbI3 film can be fully transform from dodecahedral-shaped ones enclosed by (100) and (112) facets to the cubic-shaped ones enclosed by (110) and (002) facets, while maintaining the film’s crystalline phase and composition. More importantly, such transitions are accompanied by significantly improved average PCE from 16.51±0.64% to 18.40±0.67% for the optimized CH3NH3PbI3 PSCs, benefiting from the greatly suppressed recombination and enhanced extraction of carriers.
关键词： carrier dynamics,interface engineering,perovskite solar cells,crystal facets,solution-mediated secondary growth
更新于2025-09-12 10:27:22
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Visualizing and Suppressing Nonradiative Losses in High Open-Circuit Voltage n-i-p-Type CsPbI <sub/>3</sub> Perovskite Solar Cells
摘要： Since their first demonstration in PV devices in 2009, organic-inorganic hybrid metal halide perovskites have attracted tremendous attention because of their potential applications in solution-processed photovoltaics (PV). Many research efforts, such as composition engineering and interface engineering, have been dedicated to enhancing the power conversion efficiency (PCE) of perovskite-based solar cells (PSCs) to a high level of over 24%. However, operational stability issues remain a major challenge for organic-inorganic hybrid perovskites on the way towards commercialization. Alternatively, all-inorganic perovskites (CsPbX3, X = Cl, Br, I), have received increasing interest because they are theoretically stable up to their melting points (>300 °C). Especially, CsPbI3 in the cubic phase stands out because of the lowest bandgap (of ~1.75 eV) among the all-inorganic lead-based perovskites. Compared to all other all-inorganic lead-based perovskite halide semiconductors materials which have bandgaps higher than 1.90 eV, the 1.75 eV bandgap CsPbI3 is able to absorb slightly more light in the visible region and nominally is an excellent candidate for the front cell in tandem architectures with silicon as the back cell.
关键词： open-circuit voltage,CsPbI3,perovskite solar cells,interface engineering,non-radiative losses,bulk passivation
更新于2025-09-12 10:27:22
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Titanium-carbide MXenes for work function and interface engineering in perovskite solar cells
摘要： To improve the efficiency of perovskite solar cells, careful device design and tailored interface engineering are needed to enhance optoelectronic properties and the charge extraction process at the selective electrodes. Here, we use two-dimensional transition metal carbides (MXene Ti3C2Tx) with various termination groups (Tx) to tune the work function (WF) of the perovskite absorber and the TiO2 electron transport layer (ETL), and to engineer the perovskite/ETL interface. Ultraviolet photoemission spectroscopy measurements and density functional theory calculations show that the addition of Ti3C2Tx to halide perovskite and TiO2 layers permits the tuning of the materials’ WFs without affecting other electronic properties. Moreover, the dipole induced by the Ti3C2Tx at the perovskite/ETL interface can be used to change the band alignment between these layers. The combined action of WF tuning and interface engineering can lead to substantial performance improvements in MXene-modified perovskite solar cells, as shown by the 26% increase of power conversion efficiency and hysteresis reduction with respect to reference cells without MXene.
关键词： work function,charge extraction,interface engineering,perovskite solar cells,MXene,TiO2
更新于2025-09-11 14:15:04
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Interface engineering gifts CsPbI2.25Br0.75 solar cells high performance
摘要： Organic-inorganic halide perovskite (ABX3) solar cells (PSCs) have made great progress in recent years [1]. The power conversion efficiency (PCE) has increased up to 25.2% (NREL Best Research-Cell Efficiency Chart, https://www.nrel.gov/pv/cell-efficiency.html, Accessed August 2019). However, they suffer from poor thermal stability due to the volatile A-site organic cations. All-inorganic CsPbI3–xBrx perovskite materials can tolerate temperature exceeding 400 °C, while organic–inorganic halide PSCs rapidly deteriorated at greater than 200 °C [2]. The excellent thermal stability of inorganic perovskites makes them promising materials for PSCs [3]. Their relatively low PCE is due to two reasons. One is the wide bandgap, which leads to insufficient light absorption and low Jsc. Developing tandem solar cells is an effective approach to absorb sunlight as much as possible [4]. Another is the large energy loss (Eloss), leaving much room for increasing Voc. Interface engineering can reduce the Eloss and increase the PCE. Wang et al. [5] reported a 17.06% PCE by using PTABr-treated CsPbI3 as the absorber. The post-treatment with PTABr can realize gradient Br-doping and surface passivation, leading to enhanced Voc and FF. They also modified CsPbI3 surface with choline iodine (CHI), which increased the charge-carrier lifetime and improved the energy level alignment between CsPbI3 and charge-transport layers. CHI-CsPbI3 solar cells gave a PCE of 18.4% [6]. Besides, choosing electron-transport layers (ETLs) and hole-transport layers (HTLs) with suitable energy levels is also effective for improving Voc [7]. In our previous work, we applied DPPA-modified ZnO as ETL for CsPbI2.25Br0.75 solar cells, obtaining a 15.98% PCE with an enhanced Voc [8]. Yan et al. [9] used SnO2/ZnO bilayer as ETL to get high Voc. They also used PN4N-modified SnO2 as ETL and PDCBT as HTL in CsPbI2Br solar cells, obtaining a 16.2% PCE with a 1.30 V Voc [10]. In this work, we made inorganic PSCs with a structure of ITO/SnO2/ZnO/CsPbI2.25Br0.75/HTL/MoO3/Ag (Fig. 1a). PTAA doped with polymer donor PBD2T [11] was used as HTL (D-PTAA). The deep highest occupied molecular orbital (HOMO) level of PBD2T matches HOMO of CsPbI2.25Br0.75 well. Meanwhile, PBD2T can passivate the trap states on perovskite surface and suppress interfacial charge recombination. The solar cells with D-PTAA delivered a 17.37% PCE, which is the highest efficiency for Br-doped inorganic PSCs.
关键词： High performance,Solar cells,CsPbI2.25Br0.75,Interface engineering
更新于2025-09-11 14:15:04
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Enhancement of Open‐Circuit Voltage of Perovskite Solar Cells by Interfacial Modification with <i>p</i> ‐Aminobenzoic Acid
摘要： Various approaches of interface engineering are shown to be effective in improving the device performance of organic–inorganic hybrid perovskite solar cells (PSCs). The modification of the photoactive layer of PSC, CH3NH3PbI3 (MAPbI3), by spin-coating a layer of p-aminobenzoic acid (PABA), which can significantly enhance the open-circuit voltage (VOC), the fill factor (FF), and the power conversion efficiency (PCE) of PSCs, is herein reported. The champion device shows a short-circuit current ( JSC) of 22.83 mA cm?2, VOC of 1.167 V, FF of 0.768, and PCE of 20.47%. The improvement in photovoltaic performance is attributed to the suppression of carrier trap states and the improvement in the morphologies of perovskite films. This work demonstrates a simple and effective protocol to enhance the device performance, and provides an insight into the influence of PABA post-treatment on the charge carrier dynamics.
关键词： carrier dynamics,interface engineering,p-aminobenzoic acid,postdeposition treatment,organic–inorganic hybrid perovskite
更新于2025-09-11 14:15:04
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Interface engineering with a novel n-type small organic molecule for efficient inverted perovskite solar cells
摘要： Fullerene derivatives are promising electron transporting materials for low-temperature processed inverted perovskite solar cells (PSCs). However, fullerene derivatives have some disadvantages, e.g. [6,6]-phenyl C61 butyric acid methyl ester (PCBM) has unmanageable morphology, low electron mobility and easily generated non-radiative recombination, which restrict the performance of PSCs. Herein, a novel n-type small organic molecule, homologous perylene diimide tetramer (HPDT), is designed and synthesized in this work to engineer the interface properties by enhancing interface contact, decreasing energetic barrier and recombination losses. HPDT shows suitable energy levels and high electron mobility and thus will increase the electron mobility when interface engineering in the inverted PSCs. Moreover, coating HPDT on top of perovskite prior to the deposition of PCBM is helpful to achieve a homogeneous pinhole-free PCBM layer, leading to enhanced power conversion efficiency from 17.38% up to 19.75% for inverted MAPbI3 PSCs along with a negligible hysteresis. Significantly, our results undoubtedly enable new guidelines in exploring n-type organic small molecules for high-performance PSCs.
关键词： electron transport material,perovskite solar cell,interface engineering,recombination loss
更新于2025-09-11 14:15:04
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2D Phosphorene: 2D Phosphorene: Epitaxial Growth and Interface Engineering for Electronic Devices (Adv. Mater. 47/2018)
摘要： In article number 1802207, Wei Chen and co-workers highlight their recent progress in the interface engineering of 2D phosphorene for applications in both epitaxial growth and electronic devices. Their detailed investigations reveal the critical role of substrates for epitaxial growth of 2D phosphorene, demonstrate a highly efficient surface transfer doping method, and provide a comprehensive understanding of the oxidation mechanism of black phosphorus in air.
关键词： 2D phosphorene,black phosphorus,interface engineering,surface transfer doping,oxidation mechanism,epitaxial growth,electronic devices
更新于2025-09-09 09:28:46