Efficient Carbon-based Perovskite Solar Cells Research Articles

Photo-accelerated oxidation of spiro-OMeTAD for efficient carbon-based perovskite solar cells

Photo-accelerated oxidization enables fast production of a Spiro-OMeTAD hole transport layer in perovskite solar cells. This strategy delivers high power conversion efficiency and overcomes barriers to mass manufacturing.

Ambient-air crystallization of CsPbIBr2 films with polymer towards stable and efficient carbon-based perovskite solar cells

Cesium lead mixed-halide all-inorganic perovskite solar cells (PSCs) exhibit promising balance between the efficiency and environmental stability in contrast to hybrid PSCs. Nonetheless, they face challenges due to rapid crystallization of solution processed perovskite film, resulting in elevated lattice defect density and energy loss. Therefore, a hydrophobic long-chained polymer, polypropylene carbonate (PPC) is added in varying concentrations to CsPbIBr2 precursor solution to yield a good-quality film under ambient air and low-temperature conditions. Here, the 2 % PPC added film displayed improved crystallinity and morphology and large grain-size with passivated grain-boundaries. The absorption intensity of the film was largely enhanced with reduced charge recombination and tuned energy level alignment at perovskite/carbon interface which enhanced both efficiency and stability of hole-transport layer free C–IPSCs in ambient air (humidity∼ 65–70 %). The efficiency increased upto 7.36 % which is 62.4 % higher than the bare device, attributed to its increased photovoltage (1.17 V–1.25 V), current-density (8.42 mA cm−2 to 10.25 mA cm−2), and fill-factor (46 %–57.5 %). Furthermore, optimized device has a significantly longer lifetime than bare device. Hence, this work presents a simple strategy for developing commercially feasible PSCs.

Enhanced charge extraction enabled by amide-functionalized carbon quantum dots modifier for efficient carbon-based perovskite solar cells

The effective improvement of interfacial charge extraction and inhibition of charge recombination are crucial for promoting the performance of perovskite (PVK) solar cells (PSCs). Here, the N,N’-methylenebisacrylamide-functionalized carbon quantum dots (MBA/CQDs) with defects passivation effect and appropriate energy levels are proposed as a back interface modifier for carbon-based CsPbBr3 PSCs. The functionalization of MBA molecules not only increases the content of sp2 hybrid carbon in CQDs, but also expands the passivation effect of CQDs on surface defects of PVK films by introducing carbonyl and amino groups, which improves the carrier transport and reduces the carrier nonradiative recombination. Additionally, the modification of MBA/CQDs provides an intermediate energy level at the PVK/carbon back interface, which boosts hole extraction and lowers energy loss. Finally, a leading-edge power conversion efficiency of 10.40 % is derived for the MBA/CQDs modified champion device, which is significantly improved compared to the 7.02 % efficiency for the original CsPbBr3 PSCs. Furthermore, the unpackaged CsPbBr3 PSCs with MBA/CQDs have an excellent stability, maintaining an initial efficiency of 92 % after 30 days of storage at high humidity (85 % relative humidity) and temperature (85 °C) in air.

Interface engineering toward efficient carbon-based perovskite solar cells

Interface engineering toward efficient carbon-based perovskite solar cells

Synergizing tin dioxide/perovskite interface with fluorine-doped zinc oxide for stabilized and efficient carbon-based perovskite solar cells

The new generation of solar cell technology, perovskite solar cells (PSCs), are the most promising candidates to meet global energy demands. In the current study, we improved the efficiency of their cost-effective type, i.e., carbon-based PSCs, by employing an interface engineering on the tin dioxide (SnO2) electron transport layer (ETL). A fluorine doped-zinc oxide material was used to treat the SnO2 layer and prepare a better substrate for perovskite fabrication. The fabricated perovskite layer on the treated SnO2 reveals better charge transfer, lower charge recombination, and lower leakage current. In addition, the fabricated perovskite layer on the modified ETL showed improved crystalline properties with passivated grain boundaries. As a result, a champion efficiency of 15.22% was recorded for the target carbon-based PSCs, referring to improved photovoltaic performance. Notably, the target devices showed a higher stability behavior against ambient air and kept 95% of their initial efficiency after 1658 h ageing time.

Interface engineering of Tin(IV) oxide electron transport layer with Yttrium(III) fluoride for efficient carbon-based perovskite solar cells

Carbon-based perovskite solar cells (C–PSCs) are the most promising technology to meet global energy demands at a reasonable price. In the current study, to assemble efficient and stable C–PSCs, the interface between the tin oxide electron transport layer and the mixed-cation perovskite layer was tailored by coating yttrium fluoride (YF3) material over the tin oxide layer. Results show that YF3–SnO2 ETL produces a more suitable substrate for perovskite fabrication, causing the formation of a perovskite layer with enlarged grains and a lower PbI2 residual. In addition, the results indicate that YF3 treatment could boost the conductivity of SnO2, reduce defects in the mixed-cation perovskite layer, and suppress nonradiative recombination in the C–PSCs. YF3-based interface engineering brought champion C–PSCs with an efficiency of 14.01% under simulated illumination of 100 mW cm−2, which was considerably higher than the 11.58% recorded for control C–PSCs. After 168 days of aging, the unsealed, modified C-PSC devices can demonstrate superior ambient air stability behavior conditions and retain 95% of their initial performance.

Improving the charge carrier separation efficiency at the perovskite/carbon electrode interface in HTL-free carbon-based perovskite solar cells via physical polishing

Carbon-based perovskite solar cells (C-PSCs) are favored by researchers for their low cost and support for large-scale production. However, the particles precipitated on the surface of the perovskite (PVK) film can affect the fabrication and operation of C-PSC, such as disrupting the coating of C electrode film and producing defects that can aggravate the carrier recombination. Herein a reliable and efficient C-PSC is prepared by applying a physical polishing strategy. The compact interface contact and the larger Fermi level difference at the carbon-PVK (C/PVK) interface are achieved, resulting in a 21.4% increase in power conversion efficiency compared to that without polishing. A hole-transport-layer-free C-PSC with an efficiency of 12.2% is achieved, resulting from the reduction of PVK surface roughness and defects that cause non-radiative recombination. It is revealed that the physical polishing can reduce the root mean square roughness from 15.9 nm to 1.2 nm, facilitating the screen printing of the C electrode. The carrier lifetime of the PVK film also increases from 39.9 ns to 73.3 ns, which improves the photocurrent of the solar cell. We believe that the improved C/PVK interface contact will provide a solid foundation for the future large-scale commercial production of PSCs.

Additive engineering with sodium azide material for efficient carbon-based perovskite solar cells

Electron transport layer surface modification approach to enhance overall performance of Carbon electrode based perovskite solar cell.

Impacts of plasmonic nanoparticles incorporation and interface energy alignment for highly efficient carbon-based perovskite solar cells

This work utilizes a realistic electro-optical coupled simulation to study the (i) impact of mesoporous TiO2 removal; (ii) the embedding of Ag@SiO2 and SiO2@Ag@SiO2 plasmonic nanoparticles; (iii) utilization of solution-processed inorganic p-type copper(I) thiocyanate (CuSCN) layer at the perovskite/carbon interface; and (iv) the increase of the work function of carbon electrodes (via incorporation of suitable additives/binders to the carbon ink) on the performance of carbon-based PSCs. Removal of mesoporous TiO2 increased the power conversion efficiency (PCE) of the device from 14.83 to 16.50% due to the increase in exciton generation rate and charge carriers’ mobility in the vicinity of the perovskite-compact TiO2 interface. Subsequently, variable mass ratios of Ag@SiO2 and SiO2@Ag@SiO2 plasmonic nanoparticles are embedded in the vicinity of the perovskite-compact TiO2 interface. In the optimum cases, the PCE of the devices increased to 19.72% and 18.92%, respectively, due to light trapping, scattering, and strong plasmonic fields produced by the plasmonic nanoparticles. Furthermore, adding the CuSCN layer remarkably increased the PCE of the device with a 0.93% mass ratio of Ag@SiO2 nanoparticles from 19.72 to 26.58% by a significant improvement of Voc and FF, due to the proper interfacial energy band alignment and the reduction of the recombination current density. Similar results were obtained by increasing the carbon work function, and the cell PCE was enhanced up to 26% in the optimal scenario. Our results pave the way to achieve high efficiencies in remarkably stable printable carbon-based PSCs.

Sulfur contributes to stable and efficient carbon-based perovskite solar cells

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) is already higher than those of other thin-film photovoltaic technologies, but the stability issue limits their applications. The introduction of sulfur-based compounds in PSCs could contribute to their stability. Herein, sulfur-based compounds have been embedded into each functional layer to stabilize carbon-based PSCs (C-PSCs). Results showed that the simultaneous introduction of sulfur-based compounds could decrease the trap states of perovskite film, enlarge the grain size of perovskite, and accelerate the charge transfer and extraction, leading to an improved performance. Comparing with the device without sulfide (10.77%), all sulfide C-PSCs obtained a PCE of 15.38%. The stability test showed much better resistance to humidity and thermal stress for all sulfide C-PSCs. They could retain 80% of initial PCE after aging about 700 h at relative humidity (RH) 45% ± 10% and 80 °C.

Laser fabricated carbon quantum dots in anti-solvent for highly efficient carbon-based perovskite solar cells

Additive passivation can be an effective strategy to regulate and control the properties of organic–inorganic halide perovskite film. In this article, carbon quantum dots (CQDs), fabricated by non-focused laser irradiation of carbon nanomaterial diluted in anti-solvent ethyl acetate, denoted as EACQDs, were adopted for perovskite film defect passivation and modification of carbon-based CH3NH3PbI3 perovskite solar cells (PSCs). The size of EACQDs can be tuned by manipulating the laser fluence. The morphology of perovskite film was uncovered through scanning electron microscopy and atomic force microscopy. After embedding of EACQDs, the defect in perovskite crystal was reduced, resulting in the decreased carrier recombination and accelerated carrier transportation, which were demonstrated by electrochemical impedance spectroscopy, photoluminescence and time-resolved photoluminescence. As a consequence, with the optimization of 0.01 mg/mL EACQDs (1064 nm–300 mJ·pulse−1·cm−2–10 min), the power conversion efficiency (PCE) of carbon-based PSCs achieved a maximum value of 16.43%, which improved 23.81% when compared with the pristine PSCs of 13.27%. Furthermore, the EACQDs optimized PSCs also exhibited an excellent stability and still retained 86% of its initial PCE after 50-day storage at the room atmosphere with a humidity of 30–50%.

Promoting the hole extraction and interfacial performance with MOFs derived Co3O4@NC for efficient carbon-based perovskite solar cells

Carbon-based perovskite solar cells (C-PSCs) facilitate modularization and commercialization due to their excellent thermal stability and low cost. However, C-PSCs show the poor performance that charge carrier extraction by the carbon electrode alone is not as efficient as in the case of conventional hole transport materials (HTMs) based PSCs. In this work, an inorganic hole buffer layer of nitrogen-doped carbon/Co3O4 (Co3O4@NC) nanoparticles derived from MOFs is introduced to adjust energy alignment and passivate perovskite (PSK) grain boundaries (GBs). Moreover, a simple processing method on the Co3O4@NC nanoparticles manipulated by controllable ultraviolet/ozone (UVO) treatment is employed, to further improve the interfacial performance of MAPbI3/Co3O4@NC and reduce the hysteresis. Through interface engineering, it is found that Co3O4@NC inorganic hole buffer layer effectively promotes photo‐generated charge separation and extraction, and suppresses charge recombination at the MAPbI3/Carbon electrode (CE) interface, resulting in improved photovoltaic performance. Consequently, the optimal C-PSCs without encapsulation achieved a maximum PCE of 14.63%, which is 22.3% more efficient than the pristine device (11.96%), and exhibited outstanding long-term stability.

Enhancing the optical, morphological and electronic properties of the solution-processed CsPbIBr2 films by Li doping for efficient carbon-based perovskite solar cells

CsPbIBr2 perovskite exhibits the most balanced bandgap and durability features among all the inorganic perovskites, showing great potential in the photoelectric field. Nevertheless, the poor film quality of the traditionally spin-coated CsPbIBr2 restricts the further improvement of the device performance. Here, we develop a novel lithium (Li) doping strategy to promote the optical, morphological and electronic properties of the solution-processed CsPbIBr2 perovskites. Upon incorporating Li+ ions into CsPbIBr2 lattice, highly crystallized and well-oriented CsPbIBr2 crystals are obtained. The as-prepared Li-doped CsPbIBr2 exhibits a higher film coverage over the substrate with larger grains and less grain boundaries compared to the none-doped counterparts. The trap-state densities in the CsPbIBr2 film are also effectively alleviated while the carrier lifetimes are elongated by Li doping, contributing to a lower energy loss and a higher charge collection efficiency. The optimized Li-doped perovskite solar cells (PSCs) demonstrate an excellent champion power conversion efficiency (PCE) of 9.25%, much higher than that of the none-doped devices (7.41%). Furthermore, the unencapsulated devices present a superior air and thermal stability under the protection of the hydrophobic CuPc layer and carbon electrode. Our work provides a new opportunity to fabricate cost-effective and highly efficient CsPbIBr2 PSCs in a facile way.

The synergistic effect of non-stoichiometry and Sb-doping on air-stable α-CsPbI3 for efficient carbon-based perovskite solar cells.

α-CsPbI3 with the most suitable band gap for all-inorganic perovskite solar cell (PSC) application faces an issue of phase instability at low temperature in an air atmosphere. Herein, through stoichiometric investigation, α-CsPbI3 is successfully obtained with excess CsI at 110 °C in an air atmosphere. By doping α-CsPbI3 with Sb, phase stability is further enhanced and the film morphology is also improved. Carbon-based perovskite solar cells (C-PSCs) based on CsPb0.96Sb0.04I3 achieve a promising power conversion efficiency (PCE) of 5.18%, a record value for α-CsPbI3-based PSCs without hole transport materials. Significantly, the CsPb0.96Sb0.04I3 C-PSCs retain 93% of the initial PCE after 37 days of storage in an air atmosphere. Therefore, the synergistic effect of non-stoichiometry and Sb-doping presents a promising strategy to design all-inorganic lead halide PSCs with high performance and stability.