Electrodes For Perovskite Solar Cells Research Articles

Conformal TiO2 Aerogel-Like Films by Plasma Deposition: from Omniphobic Antireflective Coatings to Perovskite Solar Cell Photoelectrodes.

The ability to control the porosity of thin oxide films is a key factor determining their properties. Despite the abundance of dry processes for synthesizing oxide porous layers, a high porosity range is typically achieved by spin-coating-based wet chemical methods. Besides, special techniques such as supercritical drying are required to replace the pore liquid with air while maintaining the porous network. In this study, we propose a new method for the fabrication of ultraporous titanium dioxide thin films at room or mild temperatures (T ≤ 120 °C) by a sequential process involving plasma deposition and etching. These films are conformal to the substrate topography even for high-aspect-ratio substrates and show percolated porosity values above 85% that are comparable to those of advanced aerogels. The films deposited at room temperature are amorphous. However, they become partly crystalline at slightly higher temperatures, presenting a distribution of anatase clusters embedded in the sponge-like open porous structure. Surprisingly, the porous structure remains after annealing the films at 450 °C in air, which increases the fraction of embedded anatase nanocrystals. The films are antireflective, omniphobic, and photoactive, becoming superhydrophilic when subjected to ultraviolet light irradiation. The supported, percolated, and nanoporous structure can be used as an electron-conducting electrode in perovskite solar cells. The properties of the cells depend on the aerogel-like film thickness, which reaches efficiencies close to those of commercial mesoporous anatase electrodes. This generic solvent-free synthesis is scalable and applicable to ultrahigh porous conformal oxides of different compositions, with potential applications in photonics, optoelectronics, energy storage, and controlled wetting.

Optimization of highly transparent DMD-films for application in perovskite solar cell

Different kinds of Dielectric/Metal/Dielectric (DMD) films have been broadly adopted as transparent electrodes of solar cells. It is crucial to simultaneously predict the D, M material and thickness which is hard accessed either by experiments or manually simulations. In this study, we employed a co-simulation approach involving transfer matrix method (TMM) and a genetic algorithm (GA) to solve this problem. It is revealed that DMD films of WO3/Ag/WO3 and AZO/Ag/AZO provide an averaged transmittance as high as ∼90% in 300–800 nm, which are expected to providing excellent front transparent electrodes for perovskite solar cells (PSCs). On this basis, 46.6% (11.8%) and 45.4% (11.3%) increment upon photocurrent and power conversion efficiency were observed compared with that of Ag (ITO) based PSC counterparts. The presented work is highly insightful for the design and application of DMD transparent electrodes, which facilitates the material and thickness of DMD films selection for future transparent electrodes of PSC.

Enhanced carbon-based back contact electrodes for perovskite solar cells: Effect of carbon paste composition on performance and stability

To address the issue of cost and instability in perovskite solar cells (PSCs), it is promising to substitute the regular hole collecting electrode i.e., spiro-OMeTAD/Au with inorganic hole transport layer (HTL)/carbon electrode. In this study, three carbon pastes were investigated with different binders: polymethyl methacrylate (PMMA), styrene-butadiene-styrene (SBS) and ethyl cellulose (EC). Carbon layers were compared in terms of mechanical stability, conductivity and performance as back contact electrodes in PSCs with an inorganic HTM composed of CuInS2 nanoparticles. To assess mechanical properties of the carbon pastes, adhesion tests by using tape, ultrasonication in the media of deionized water and acidic deionized water, and also flexibility test were performed. The carbon layer based on SBS carbon paste (SBS-CP) was intact after adhesion tests and over 1017 cycles of flexibility test. The one based on PMMA carbon paste (PMMA-CP) didn't tolerate all mechanical tests and disintegrated. The carbon layer based on EC carbon paste (EC-CP) partly damaged after adhesion tests and didn't pass the flexibility test. The best efficiency of 18.6 % was obtained for a device based on SBS-CP and significant shelf-life stability over 172 days stored in relative humidity of 40 % and dark.

Enhancing Performance and Stability of p-i-n Perovskite Solar Cells with Ag-Cu Codeposited Alloy Electrodes.

In the development of back electrodes for perovskite solar cells (PSCs), the major challenges are stability and cost. To address this, we present an innovative approach: Simultaneous evaporation of two independently controlled sources of metal materials was performed to achieve a uniform distribution of the alloy electrodes. In this study, Ag-Cu alloys (the molar ratio of Ag/Cu is 7/3) with a high-index crystal face (111) and a work function matching perovskite were prepared using a codeposition technique. These properties mitigate nonradiative carrier recombination at the interface and reduce the energy barrier for carrier migration. Consequently, compared to Ag based PSCs (22.77%), the implementation of Ag-Cu alloy (Ag/Cu is 7/3)-based PSCs resulted in a power conversion efficiency of 23.72%. In a 1500 h tracking test in ambient air, the Ag-Cu alloy (Ag/Cu is 7/3)-based PSCs maintained their initial efficiency of 86%. This can be attributed to almost no migration of elements from the Ag-Cu alloy electrode to the perovskite layer. Our work presents a vital strategy for improving the stability of PSCs and reducing the costs associated with the back electrode in PSCs.

Mass scale synthesis of graphene nanosheets using waste cardboard for application in perovskite solar cells and supercapacitors

Advanced graphene-based materials have been proficiently incorporated into next-generation solar cells and supercapacitors because of their high electrical conductivity, large surface area, excellent charge-transport ability, and exceptional optical properties. Herein, we report the synthesis of graphene nanosheets (GNs) from waste cardboard via pyrolysis, with ethyl alcohol as the growth initiator. Additionally, we demonstrated the use of GNs in energy conversion and storage applications. Using the GN electrode in perovskite solar cells resulted in an excellent power conversion efficiency of ∼10.41 % for an active area of 1 cm2, indicating an enhancement of approximately 27 % compared to conventional electrodes. Furthermore, the GNs were used as active electrode materials in supercapacitors with excellent electrochemical performance and a high gravimetric specific capacitance of 167.5 F/g at a scan rate of 2 mV/s. The developed GNs can be efficiently used for energy storage, conversion, and electrochemical sensing applications.

Transferred Metal Electrodes for Perovskite Solar Cells with Doping‐Tuned Hole‐Transporting Layer

As an alternative technology to the standard evaporated metal top electrode in perovskite solar cells, the transfer method top electrode is featured with low cost, simple process, and ease of scalability. However, as the transfer method preparation of the less expensive metal electrodes (Ag and Cu) is explored, the mismatch between the hole‐transport layer and the top electrode results in anomalous photovoltaic properties. In this study, the work function of the hole‐transporting material is adjusted by changing the dopant content to achieve a good energy‐level match with either Ag or Cu electrode material. The power conversion efficiencies of perovskite devices based on transferred Ag and Cu electrodes can reach 18.41% and 17.25%, respectively, which are comparable to the performance of the evaporated top electrode devices.

Polymer-acid-metal quasi-ohmic contact for stable perovskite solar cells beyond a 20,000-hour extrapolated lifetime

The development of a robust quasi-ohmic contact with minimal resistance, good stability and cost-effectiveness is crucial for perovskite solar cells. We introduce a generic approach featuring a Lewis-acid layer sandwiched between dopant-free semicrystalline polymer and metal electrode in perovskite solar cells, resulting in an ideal quasi-ohmic contact even at elevated temperature up to 85 °C. The solubility of Lewis acid in alcohol facilitates nondestructive solution processing on top of polymer, which boosts hole injection from polymer into metal by two orders of magnitude. By integrating the polymer-acid-metal structure into solar cells, devices exhibit remarkable resilience, retaining 96% ± 3%, 96% ± 2% and 75% ± 7% of their initial efficiencies after continuous operation in nitrogen at 35 °C for 2212 h, 55 °C for 1650 h and 85 °C for 937 h, respectively. Leveraging the Arrhenius relation, we project an impressive T80 lifetime of 26,126 h at 30 °C.

Application of Carbon Materials in Conductive Electrodes for Perovskite Solar Cells

Over the past decade, perovskite solar cells (PSCs) have achieved significant achievements. But the golden triangle problem of commercial development, which encompasses high efficiency, high stability, and low cost, remains unresolved. Carbon materials exhibit a diverse range of morphological structures and possess numerous advantages. They are extensively used in PSCs to overcome the challenges encountered during PSCs commercialization. The PSCs utilizing graphene as the top electrodes not only deliver an impressive efficiency of 22.8%, but also show exceptional long‐term stability. The PSCs using carbon nanotubes as transparent conductive electrodes obtain an efficiency of 19%, exhibiting significant potential for scalable applications. Herein, the advantages of carbon materials as conductive electrodes are overviewed. The compatibility of carbon materials as conductive electrodes in PSCs, along with the associated challenges, regulatory strategies, and device performance are systematically discussed in terms of their intrinsic characteristics. The application of carbon materials derived from petroleum by‐products and biomass in the top electrodes of PSCs are summarized in detail. Finally, the underlying reasons why PSCs using carbon electrode show a comparatively lower efficiency when compared to conventional devices is analyzed in‐depth. The potential research directions are proposed to promote the development of carbon conductive electrodes in PSCs.

Carbon Electrodes for Perovskite Photovoltaics: Interfacial Properties, Meta‐analysis, and Prospects

Carbon electrodes have gained significant attention as a cost‐effective, sustainable, stable, and scalable replacement for metal electrodes in perovskite solar cells (PSCs). However, traditional carbon‐electrode‐based PSCs (C‐PSCs) lack a hole‐selective layer (HSL) due to their incompatibility with the most effective organic HSLs employed in the PSC literature. In turn, the absence of an HSL has been identified as one of the main factors hindering the performance of C‐PSCs. Consequently, numerous studies have recognized the pivotal significance of the region between the perovskite absorber and the carbon electrode in C‐PSCs, proposing various interfacial engineering strategies to improve the performance of these solar cells. Given the rapid evolution of this field, an up‐to‐date and comprehensive review of C‐PSCs is in order. Key areas of focus of this review include the shift from high‐temperature to low‐temperature carbon electrodes, strategies to improve energetic alignment at the interface, novel approaches such as hole‐selective bilayers, and alternative carbon deposition methods to reduce solvent damage. Additionally, this review presents a comprehensive meta‐analysis—the first of its kind in the C‐PSC literature—to assess how various interfacial modifications impact critical C‐PSC performance metrics, offering valuable insights for future advancements in the field.

Probing the Key Roles of Back-Interface in Performance of Carbon-Based Hole-Transport-Layer Free Perovskite Solar Cells

Carbon electrodes have gained widespread attention as a sustainable, stable, and low-cost alternative to metal electrodes in perovskite solar cells (PSCs). However, the power conversion efficiency (PCE) of the carbon...

NiOx/PANI nanocomposite doped carbon paste as electrode for long-term stable and highly efficient perovskite solar cells.

Carbon-based perovskite solar cells (PSCs) have emerged as a hopeful alternative in the realm of photovoltaics. They are considered promising due to their affordability, remarkable durability in humid environments, and impressive electrical conductivity. One approach to address the cost issue is to use affordable counter electrodes in PSCs that do not require organic hole transport materials (HTMs). This study utilized an innovative and economical method to create NiOx/PANI nanocomposites. Later, these nanoparticles were integrated into a carbon paste to act as an HTM. This incorporation is intended to optimize charge extraction, improve interfacial contact, align energy levels, reduce energy loss, minimize charge recombination, and protect the perovskite (FAPbI3) surface from degradation. The optoelectronic properties of these devices were investigated, and all cells showed improved efficiency compared to control cells. The NiOx/PANI doped carbon (NiOx/PANI+CE) exhibited excellent performance due to strong hole conductivity, well-aligned energy levels, and the formation of stepwise band alignment at the perovskite interface.

Liquid Metal‐Based Perovskite Solar Cells: In Situ Formed Gallium Oxide Interlayer Improves Stability and Efficiency

AbstractIn this study, eutectic gallium–indium alloy (EGaIn) liquid metal is used as the rear electrode for perovskite solar cells (PSCs), where the interfacial properties of the device, particularly the beneficial roles of the surface oxide of the liquid metal, are explored. The findings demonstrate that the native oxide of the EGaIn electrode significantly affects the stability of photovoltaic performance and impedance characteristics including series and shunt resistances. Based on the results, the following hypothesis is formulated: the oxide interlayer serves two crucial functions of a barrier against metal diffusion and a tunnel for enhancing charge extraction and transfer. The results of elemental mapping and trap density calculation support the former function of the hypothesis that the oxide film can effectively prevent metal penetration into the perovskite layer. Furthermore, measurements involving capacitance−voltage and time‐resolved photoluminescence confirm that the oxide film on the liquid metal eliminates the interfacial Schottky barrier, promoting efficient charge extraction and transfer processes. Finally, the investigation is extended to develop flexible PSCs using the EGaIn electrode, which consistently exhibits stable performance during repeated bending cycles. Notably, the EGaIn rear electrode can be readily removed and collected through a straightforward acid treatment, offering a promising avenue for efficient cell recycling.

Fabrication of a Water-Stripped Free-Standing Silver Nanowire Network as the Top Electrode for Perovskite Solar Cells

Fabrication of a Water-Stripped Free-Standing Silver Nanowire Network as the Top Electrode for Perovskite Solar Cells

Influence of metal salts (Al, Ca, and Mg) on the work function and hole extraction at carbon counter electrodes in perovskite solar cells

Hole transport material-free carbon-based perovskite solar cells (HTM-free C–PSCs) are recognized as a cost-effective and stable alternative to conventional perovskite solar cells. However, the significant energy level misalignment between the perovskite layer and the carbon counter electrode (CE) results in ineffective hole extraction and unfavorable charge recombination, which decreases the power conversion efficiency (PCE). Here, we report the introduction of metal salts (Al, Ca, and Mg) into graphite/carbon black (Gr/CB) CEs to modify the work function and enhance the hole selectivity of the CE. This modification leads to improved energy level alignment, efficient hole extraction, and reduced charge recombination. The PCE of the HTM-free C-PSC based on Al-modified Gr/CB as the CE material reached 9.91%, which is approximately 12% higher than that of devices employing unmodified Gr/CB CEs. This work demonstrates that by directly incorporating metal salts into the Gr/CB CE, the energy level alignment and hole extraction at the perovskite/carbon interface can be improved. This presents a viable method for enhancing the PCE of HTM-free C–PSCs.

Quantifying and Reducing Ion Migration in Metal Halide Perovskites through Control of Mobile Ions.

The presence of intrinsic ion migration in metal halide perovskites (MHPs) is one of the main reasons that perovskite solar cells (PSCs) are not stable under operation. In this work, we quantify the ion migration of PSCs and MHP thin films in terms of mobile ion concentration (No) and ionic mobility (µ) and demonstrate that No has a larger impact on device stability. We study the effect of small alkali metal A-site cation additives (e.g., Na+, K+, and Rb+) on ion migration. We show that the influence of moisture and cation additive on No is less significant than the choice of top electrode in PSCs. We also show that No in PSCs remains constant with an increase in temperature but μ increases with temperature because the activation energy is lower than that of ion formation. This work gives design principles regarding the importance of passivation and the effects of operational conditions on ion migration.

Spiro-OMeTAD versus PTAA for single-walled carbon nanotubes electrode in perovskite solar cells

Poly(triarylamine) (PTAA)-wrapped single-walled carbon nanotubes (SWCNTs) functioned in a dual role as an efficient hole-transporting layer and electrode in perovskite solar cells (PSCs). Thanks to the well-matched energy level, increased hole-transporting mobility, and hydrophobicity rendered by dopant-free PTAA, this dual-role SWCNTs electrode applied-PSCs using dopant-free PTAA achieved a better efficiency and stability than reference standards using LiTFSI-doped Spiro-OMeTAD. This dopant-free PTAA-applied SWCNTs electrode is expected to not only give a solution for efficiently using the SWCNTs electrode in PSCs, but also unveil the mechanism of the interaction between the hole-transporting layer and SWCNTs.

Advances in the research of carbon electrodes for perovskite solar cells.

Perovskite solar cells (PSCs) were first proposed in 2009. They have the advantages of low cost, a simple manufacturing process and excellent photoelectric performance. PSC electrodes are mainly made from precious metals such as gold and silver. Still, the cost of precious metals is high and they react with the other components of the PSCs, resulting in the poor stability of the photovoltaic device. Using carbon as an electrode material can both reduce the cost and significantly improve the stability of the photovoltaic device. However, the poor interface contact between the carbon electrode and perovskite and carbon electrode resistance results in poor photovoltaic device photoelectric performance. Finding a way to successfully utilize carbon as an alternative electrode material is a key step toward moving PSCs from the laboratory to industrialization. This paper reviews the application of carbon black, graphite, graphene, carbon nanotubes (CNTs) and composite carbon electrode in PSCs, focusing on progress in the research of doping, structure, interface modification and the production process.

Unveiling and overcoming the interfacial degradation between CuSCN and metal electrodes in perovskite solar cells

The interfacial degradation at the CuSCN/Au interface due to Au–Cu alloying can be improved by replacing Au with carbon electrodes, delivering high device stability under light illumination.

Sprayed and mechanical-modified graphite layer as transferred electrode for high-efficiency perovskite solar cells

As an alternative of evaporated metal top electrode in perovskite solar cells, the transferred top electrode technique has the outstanding advantage of simple process. And in the case of carbon based transferred top electrode, the efficiency of corresponding perovskite devices can be higher than 20%. During the solid-to-solid electrode transferring process, it is essential to achieve effective contact and to avoid damage of bottom functional layers for an improved device performance. In this work, a sprayed graphite layer on conductive substrate is employed as transferred top electrode for perovskite solar cells. A simple mechanical polishing treatment is further adopted to modify the surface status of graphite layer. Compared with as sprayed graphite electrode, polished electrode shows better electrical property and optimized interface contact with hole-transporting layer. Thus, the average efficiency of perovskite device with mechanical modified electrode can significantly increase from 16.3% to 19.2%.

Synthesis and application of silver and copper nanowires in high transparent solar cells

Electrodes in new function-flexible optoelectronic devices, need to meet the requirements of foldability and high transmittance. In last decades, thousands of research about copper and silver nanowires promoted the prosperity of photovoltaic industry. In this paper, we focus on the recent progresses of silver and copper nanowires for high transparent solar cell application, including preparation and optimization techniques. In addition, the primary obstacles of nanowire transparent electrodes in perovskite solar cells, organic solar cells and dye sensitized solar cells were discussed. Finally, the application prospects of nanowire-based high transparent solar cells were outlined.