Electrodes For Perovskite Solar Cells Research Articles

Vacuum‐Assisted Laminating Preparation for Carbon Film Electrode in Perovskite Solar Cells

As an alternative to an evaporated metal top electrode, the carbon film electrode has been successfully applied to small‐area rigid and flexible perovskite solar cells by a pressing transfer method. However, the plate‐to‐plate laminating process for the carbon film electrodes deposition has some shortcomings, such as the uneven and uncertain actual loaded pressure on device. Herein, the carbon film‐based top electrode is laminated onto the perovskite device via a vacuum‐assisted pressing technique with an automatic solar panel laminator. Compared with manual and pneumatic plate pressing, the vacuum laminating process can reduce the roughness of the carbon film and increase the contact area under relatively low working pressure. Consequently, the perovskite solar cells with vacuum laminated carbon electrodes can achieve a relatively high efficiency of 18.3% and exhibit application prospect for reproducible mass fabrication.

In situ growth of graphene on both sides of a Cu–Ni alloy electrode for perovskite solar cells with improved stability

The instability of rear electrodes undermines the long-term operational durability of efficient perovskite solar cells. Here, a composite electrode of copper–nickel (Cu–Ni) alloy stabilized by in situ grown bifacial graphene is designed. The alloying makes the work function of Cu suitable for regular perovskite solar cells. Cu–Ni is the ideal substrate for preparing high-quality graphene via chemical vapour deposition, which simultaneously protects the device from oxygen, water and reactions between internal components. To rivet the composite electrode with the semi-device, a thermoplastic copolymer is applied as an adhesive layer through hot pressing. The resulting devices achieve power conversion efficiencies of 24.34% and 20.76% (certified 20.86%) with aperture areas of 0.09 and 1.02 cm2, respectively. The devices show improved stability: 97% of their initial efficiency is retained after 1,440 hours of a damp-heat test at 85 °C with a relative humidity of 85%; 95% of their initial efficiency is retained after 5,000 hours at maximum power point tracking under continuous 1 sun illumination.

Photovoltaic Properties of ZnO Films Co-Doped with Mn and La to Enhance Solar Cell Efficiency.

In the present investigation, ZnO films co-doped with Mn and La were synthesized by the sol–gel technique. XRD analysis revealed that ZnO had a hexagonal structure. Mixed hexagonal and cubic phases appeared in ZnO containing Mn (1%) and La (1.5%). The grain size, d-spacing, unit cell, lattice parameters, atomic packing fraction, volume, strain, crystallinity, and bond length of co-doped ZnO films were determined as a function of doped ion contents. Through UV analysis, it was found that pristine ZnO had Eg = 3.5 eV, and it decreased when increasing the doping concentration, reaching the minimum value for the sample with 1% Mn and 1% La. The optical parameters of the films, such as absorption, transmittance, dielectric constants, and refractive index, were also analyzed. DSSCs were fabricated using the prepared ZnO films. For pure ZnO film, the values were: efficiency = 0.69%, current density = 2.5 mAcm−2, and open-circuit voltage = 0.56 V. When ZnO was co-doped with Mn and La, the efficiency increased significantly. DSSCs with a ZnO photoanode co-doped with 1% Mn and 1% La exhibited maximum values of Jsc = 4.28 mAcm−2, Voc = 0.6 V, and efficiency = 1.89%, which is 174% better than pristine ZnO-based DSSCs. This material is good for the electrode of perovskite solar cells.

Recent Developments in Upscalable Printing Techniques for Perovskite Solar Cells.

Just over a decade, perovskite solar cells (PSCs) have been emerged as a next‐generation photovoltaic technology due to their skyrocketing power conversion efficiency (PCE), low cost, and easy manufacturing techniques compared to Si solar cells. Several methods and procedures have been developed to fabricate high‐quality perovskite films to improve the scalability and commercialize PSCs. Recently, several printing technologies such as blade‐coating, slot‐die coating, spray coating, flexographic printing, gravure printing, screen printing, and inkjet printing have been found to be very effective in controlling film formation and improving the PCE of over 21%. This review summarizes the intensive research efforts given for these printing techniques to scale up the perovskite films as well as the hole transport layer (HTL), the electron transport layer (ETL), and electrodes for PSCs. In the end, this review presents a description of the future research scope to overcome the challenges being faced in the printing techniques for the commercialization of PSCs.

Multi‐Functional MoO3 Doping of Carbon‐Nanotube Top Electrodes for Highly Transparent and Efficient Semi‐Transparent Perovskite Solar Cells

AbstractMoO3 doping of carbon‐nanotube top electrodes in perovskite solar cells is multi‐functional and facilitates p‐doping, favorable energy‐level alignment, and enhanced hole transport. The optimal layer thickness of MoO3 (8 nm) is determined for decreasing the sheet resistance of carbon‐nanotube electrodes without damaging the perovskite film. The sheet resistance decreases by approximately one‐third from its original value, which is a substantially better result than that previously reported for acid doping of carbon‐nanotube top electrodes. MoO3 deposition lowers the Fermi level of the carbon‐nanotube electrode, improving its energy‐level alignment and hole‐transfer performance. When coated with 2,2′,7,7′‐tetrakis[N,N‐di(4‐methoxyphenyl)amino]‐9,9′‐spirobifluorene (spiro‐MeOTAD), MoO3 crystallizes on the carbon nanotubes and further enhances hole collection. Semi‐transparent perovskite solar cells with MoO3‐doped carbon‐nanotube electrodes have a power conversion efficiency of 17.3% with a transmittance of approximately 60% (at a wavelength of 1000 nm). Because of their favorable transparency in the infrared region, these perovskite solar cells are evaluated for use in a tandem structure with silicon solar cells via computational simulations. The predicted device efficiency (23.7%) exceeds that of conventional indium‐tin‐oxide‐based tandem solar cells (23.0%).

Effect of Annealing in ITO Film Prepared at Various Argon-and-Oxygen-Mixture Ratios via Facing-Target Sputtering for Transparent Electrode of Perovskite Solar Cells

Normal perovskite solar cells (PSCs) consist of the following layers: transparent electrode, electron-transport layer (ETL), light-absorbing perovskite layer, hole-transport layer (HTL), and metal electrode. Energy, such as electricity, is produced through light absorbance and electron–hole generation/transport between two electrode types (metal film and transparent conducting film). Among stacked layers in a PSC, the transparent electrode plays the high-performance-power-conversion-efficiency role. Transparent electrodes should have high-visible-range transparency and low resistance. Therefore, in this study, we prepared indium tin oxide (ITO) films on a glass substrate by using facing-target sputtering without substrate heating treatment and investigate the heating-treatment effect on the ITO-film properties for perovskite solar cells (PSCs). Moreover, we fabricated PSCs with ITO films prepared at various oxygen flows during the sputtering process, and their energy-conversion properties are investigated.

Recent Development and Directions in Printed Perovskite Solar Cells

Just over a decade ago, perovskite solar cells (PSCs) established themselves as the next generation of photovoltaic technology due to their comparably higher power conversion efficiency (PCE) (25.6%), cheaper and simpler manufacturing processes to that of Silicon solar cells. Based on the potential, several methods and processes have been developed to produce high‐quality perovskite films for commercialization of PSCs. It has recently been found that printing technology is very effective in controlling film formation, resulting in a high PCE of over 21%. This review summarizes the intense research that has been done on newer printing techniques to enlarge perovskite films and other layers such as the hole transport layer (HTL), the electron transport layer (ETL), and electrodes for PSCs. At the end, the review article describes the future scope of research to address the challenges of commercializing PSCs.

Counter electrodes for perovskite solar cells: materials, interfaces and device stability

This review summarizes recent advances in rear counter electrodes for perovskite solar cells, including alternative materials, interfaces and device stability.

Laminated high-performance semi-transparent perovsktie solar cells: Enabled by sticky polyethyleminine as glue

Electric glue plays a key role in laminating top electrodes for organic and perovskite thin-film solar cells. However, there has been seldom reported for chemically reactive low–work function electrode yet. In this paper, polyethyleneimine (PEI) was developed as transparent top electrode adhesive, surface modifier for air-stable low–work function, and barrier to suppress the chemical corrosion of metal electrode in perovskite solar cells. The lamination was finished under room temperature with a pressure as low as 8 MPa, which is a very mild condition for device fabrication. The solar cells with transparent top electrode laminated for 10min had the best performances, in which the average value of PEI thickness between silver nanowires and the adjacent layer was found to play a key role in adjusting the performance of solar cells.

Low-Temperature Deposited Highly Flexible In–Zn–V–O Transparent Conductive Electrode for Perovskite Solar Cells

Inorganic–organic hybrid perovskite solar cells (PSCs) typically embrace Sn-doped In2O3 (ITO) and F-doped SnO2 (FTO) as transparent electrodes, which are rigid and brittle, retarding the commercialization of flexible PSCs (FPSCs). Here, we fabricated flexible amorphous transparent V-doped In–Zn–O (IZVO) thin films with varied concentrations of V atoms at room temperature. The impacts of V concentration on the chemical, electrical, and optical properties of IZVO thin films were thoroughly investigated. The incorporation of V into IZO was demonstrated to suppress the formation of oxygen vacancies and thus reduce the carrier concentration in IZO. The IZVO thin film affords the best electrode performance with an optimum V concentration of 0.46 atom %. In contrast to the conventional ITO transparent electrodes that require a high processing temperature, the amorphous transparent IZVO electrode deposited at a low temperature without any heating and postannealing process showed a low sheet resistance (∼22.6 Ω/□), high conductivity (∼2210 S/cm), high optical transmittance (∼88.8%), and in particular, excellent mechanical flexibility and fatigue robustness. Therefore, the amorphous transparent IZVO electrode-based perovskite solar cells (PSCs) showed superior performance (14.57%) compared to the amorphous ITO electrode-based PSCs (11.96%), due to the significantly improved short-circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF). Moreover, the IZVO electrode-based FPSC device retained 77% of its initial power conversion efficiency (PCE) after 100 bending cycles, while the PCE of the amorphous ITO electrode-based FPSC dropped by 80% after only 30 bending cycles. Combining the excellent mechanical flexibility and fatigue robustness, the flexible amorphous IZVO electrode shows great potential for highly efficient flexible photovoltaic applications.

ITO/SnO2 Interface Defect Passivation via Atomic Layer Deposited Al2O3 for High‐Efficiency Perovskite Solar Cells

Indium tin oxide (ITO) substrate is widely used as a transparent electrode in perovskite solar cells (PSCs). However, the intrinsic defects, especially on the ITO surface, are one of the most key factors to restrict the power conversion efficiency (PCE) of PSCs. Herein, a facile method to passivate the defects of the ITO/SnO2 interface using an ultrathin aluminum oxide (Al2O3) layer through atomic layer deposition, of which the film thickness is exactly regulated, is first demonstrated. With the optimized film thickness, carrier recombination at the ITO/SnO2 interface is effectively suppressed within the three‐cycle Al2O3 layer, which results in an improved charge carrier collection efficiency from the SnO2 electron transporting layer to the ITO electrode. Furthermore, a thinner Al2O3 film (one cycle) does not passivate the interface defect effectively, and a thicker Al2O3 film (five cycles) retards the charge carrier extraction at the ITO/SnO2 interface. The average PCE of the three‐cycle Al2O3‐based PSC is 19.43%, among which the champion PCE is 20.24%, showing a significant improvement compared with the counterpart with an average PCE of 18.50%.

Scalable, efficient and flexible perovskite solar cells with carbon film based electrode

Compared with traditional rigid perovskite solar cells fabricated on glass, flexible perovskite solar cells have a wider range of applications due to their lightweight and bendability, which have attracted great attention. Besides, carbon materials have shown some advantages of abundance, long-term stability and appropriate energy level as top electrode in perovskite solar cells. However, the reports of flexible devices based on carbon electrode are quite rare for the mismatch between the configuration of flexible perovskite solar cells and common carbon electrode techniques. Here, we introduce carbon film electrode into flexible perovskite solar cells for the first time. A new composite carbon film electrode is prepared on a highly conductive and flexible substrate of conductive cloth. Considerable PCEs of 15.37% and 14.05% have been obtained in small area (0.1 cm 2 ) and large area (1 cm 2 ) carbon based flexible devices, respectively. The comparable performance with standard Au electrode device, enhanced stability and suitability for roll-to-roll manufacturing reveals promising application of this low-cost composite carbon electrode. • Carbon film electrodes were introduced into flexible perovskite solar cells. • Efficiency of carbon based rigid perovskite solar cells reached 19.36%. • 15.37% and 14.05% were obtained in 0.1 cm 2 and 1 cm 2 flexible devices respectively.

Recent Progresses in Carbon Counter Electrode Materials for Perovskite Solar Cells and Modules

AbstractThough perovskite solar cells (PSCs) or modules (PSMs) are being developed at an unprecedented speed, several obstacles remain to their commercialization. One of the difficult problems is the expensive and unstable Au and Ag counter electrode. Therefore, highly effective, stable, and low‐cost counter electrode materials should be explored. Among various counter electrode materials, carbon is one of the most promising substitutes for their rich sources, low cost, outstanding electrochemical performance, and diversified surface functions. This review summarizes recent achievements of carbon counter electrode materials, which included commercial carbon paste, carbon black, graphite, graphene, carbon nanotubes and their synthetic approaches, modifications, and structure‐function relationships. Moreover, large‐scale carbon counter electrode in PSCs or PSMs are specifically discussed. Hopefully, this recapitulative analysis will draw the attention of relevant researchers to re‐understand the importance of counter electrode and clarify what should be noticed to develop qualified counter electrode materials for PSCs or PSMs.

Cellulose‐Based Oxygen‐Rich Activated Carbon for Printable Mesoscopic Perovskite Solar Cells

Carbon electrodes (CEs) are demonstrated as the most stable and cost‐effective back electrodes for perovskite solar cells (PSCs), which influence the performance of related PSCs significantly. Herein, oxygen‐rich activated carbon (AC) is synthesized from the most abundant biomass resource, cellulose, via a feasible carbonization and oxidization process and applied in CEs for hole‐conductor‐free printable mesoscopic PSCs (p‐MPSCs). The obtained cellulose‐based activated carbon (CAC) exhibits a high specific area of 477.14 m2 g−1 and possesses a high oxygen content of 11.9%, promoting the wettability and contact between CEs and perovskites. Moreover, the high oxygen content also leads to an elevated work function of CEs. As a result, p‐MPSCs filled with (5‐AVA)0.03(MA)0.97PbI3 based on CEs containing CAC give an efficiency of 15.5%, whereas those devices based on CEs with no CAC give an efficiency of 13.8%. The improved efficiency benefits from the promoted fill factor and open circuit voltage due to the optimized energy level alignment and enhanced charge extraction by CAC. This work presents a good example for the value‐added utilization of cellulose in the energy conversion systems and offers a feasible strategy for preparing oxygen‐rich CE for PSCs with enhanced performance.

Optimum silver contact sputtering parameters for efficient perovskite solar cell fabrication

The use of magnetron sputtering for deposition of the metal electrode in perovskite solar cells has been limited because of the damage to the organic hole transport layer by high kinetic energy particles during the sputtering process. In this paper, a systematic investigation into the effect of sputtering power, argon flow rate, sputtering duration, and argon pressure on the performance of the perovskite cells was conducted. The results of this work show that high power conversion efficiency of 18.35% was obtained for solution-processed, air-fabricated perovskite solar cells with Ag contact prepared using magnetron sputtering. The devices also exhibit an excellent short-current density of 22.56 mA/cm2, an open-circuit voltage of 1.10 V and a fill factor of 73.7%. The investigation reveals that sputtering power is the most critical factor that needs to be carefully controlled to minimise the damage to the hole transport layer. This study demonstrates that highly efficient perovskite solar cells can be fabricated using magnetron sputtering if the sputtering parameters are optimised.

Room-temperature carbon electrodes with ethanol solvent interlacing process for efficient and stable planar hybrid perovskite solar cells

Among the next-generation photovoltaic technologies, perovskite solar cells (PSCs) have attracted significant attention and interest. However, PSCs typically use high-vacuum processed metal electrodes, which are considerably more expensive. Furthermore, this process using noble metals, results in dramatic performance degradation after halide ion migration and thermal stress. Therefore, replacing metal electrodes with carbon electrodes is a promising way to address the stability issues of PSCs. This is due to carbon materials possessing unique qualities, such as low cost, high stability, good conductivity, and inherent water resistance. In contrast, some solvents in commercial carbon paste cause damage to the structure of perovskite films. Herein, room-temperature carbon films were successfully prepared utilizing an ethanol solvent interlacing process with time optimization. The resulting carbon films exhibited good flexibility inducing tight adhesion onto the hole transporting layer as well as excellent electrical properties. The carbon films were then applied as working electrodes in PSCs structured as FTO/TiO2/Cs0.17FA0.83Pb(I0.83Br0.17)3/spiro-OMeTAD/carbon. By optimizing time, in the ethanol solvent interlacing process, an excellent power conversion efficiency (PCE) was achieved. The devices improved up to 12.2% using the soaked carbon films at 2 h. Moreover, the device exhibits excellent long-term stability of 80% over 1000 h in air environment without encapsulation. Finally, this simple and effective technique proposes an alternate choice for developing efficient carbon-based PSCs.

Comparison of highly conductive natural and synthetic graphites for electrodes in perovskite solar cells

In this work we compare seven different types of natural and synthetic graphite particles and examine how their integration into the cathode of carbon-based perovskite solar cells (C–PSCs) is influencing their opto-electronic properties. By combining x-ray diffraction, Raman spectroscopy and 4-point probe measurements we show that the differences in graphite crystallinity significantly affect the sheet resistance of the carbon-based cathode. The most conductive carbon-based film with an exceptional sheet resistance of 4 Ω/sq. have been produced from scaly graphite with the crystallite dimensions of La = 60.6 nm and Lc = 28.6 nm. Electrochemical Impedance Spectroscopy further revealed that charge transfer resistance at the perovskite/carbon contact differ for each graphite type. Overall, the pyrolytic graphite was found to be the best compromise between high conductivity and low charge transfer resistance leading to least series resistance losses and a fill factor (FF) above 74% (in perovskite solar cells with area of 0.64 cm2). However, an overall efficient hole extraction and lower non-radiative charge recombination in C–PSCs with scaly graphite resulted in the highest average power conversion efficiency and a champion device reaching 14.63%. All the C–PSCs show exceptional moisture stability for 5,000 h under ambient condition, with a PCE decrease of less than 3%.

M13 bacteriophage-templated gold nanowires as stretchable electrodes in perovskite solar cells

This work reports stretchable gold nanowires grown on M13 bacteriophage in perovskite solar cells, which is the first demonstration of the M13 virus as a stretchable transparent electrode.

Carbon-based electrodes for perovskite solar cells

The cost-effective processability and high stability of carbon-based perovskite solar cells (C-PSCs) have shown great potential to positively devote to the development of large-scale production processes.

Recent Advances in Carbon Nanotube Utilizations in Perovskite Solar Cells

AbstractMetal halide perovskite solar cells (PSCs) have emerged as promising next‐generation photovoltaic devices with the maximum output efficiency exceeding 25%. Despite significant advances, there are many challenges to achieve high efficiency, stability, and low‐cost simultaneously. Combating these challenges depends on developing novel materials and modifying conventional device components. Carbon nanotubes (CNTs) have attracted considerable attention for fabricating efficient PSCs owing to their remarkable electrical, optical, and mechanical properties. With their multifunctional features, CNTs can play a wide range of roles and offer unique benefits in various components in PSCs to improve device performance and durability. Here, recent progress concerning the utilizations of CNTs as transparent conductive electrodes, charge‐transporter, perovskite additives, interlayers, hole‐transporting materials, and back electrodes in PSCs is comprehensively reviewed. The application of CNTs toward the development of 1D and 2D flexible PSCs is also discussed. A summary of current challenges and prospective on future research directions of employing CNTs to realize high‐performance PSCs is presented.