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Due to the loss of organic amine cations and lead ions in the structure of the iodine–lead methylamine perovskite solar cell, there are a large number of defects within the film and the recombination loss caused by grain boundaries, which seriously hinder the further improvement of power conversion efficiency and stability. Herein, a novel carbon nitride C3N3 incorporated into the perovskite precursor solution is a multifunctional strategy, which not only increases the light absorption strength, grain size, and hydrophobicity of the perovskite film, but also effectively passivates the bulk and interfacial defects of perovskite and verified by the first‐principles density functional theory calculations. As a result, the efficiency and stability of perovskite solar cells are improved. The device with 0.075 mg mL−1 C3N3 additive delivers a champion power conversion efficiency of 19.91% with suppressed hysteresis, which is significantly higher than the 18.16% of the control device. In addition, the open‐circuit voltage of the modified device with the maximum addition as high as 1.137 V is 90.96% of the Shockley–Queisser limit (1.25 V). Moreover, the power conversion efficiency of the modified device without encapsulation can maintain nearly 90% of its initial value after being stored at 25 °C and 60% relative humidity for 500 h. This work provides a new idea for developing additives to improve the power conversion efficiency and stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have achieved unprecedented power conversion efficiency improvements, and further development is stepping to industrialization. In terms of industrial manufacturing, simplifying the solar cell structure is critical in both fabrication process design and cost control. Due to the bipolar charge transport nature of perovskites, the elimination of the charge carrier transport layer is possible. Herein, EMIMPF6 ionic liquid is incorporated into the perovskite film to modulate the energy‐level alignment and the charge transfer kinetics, demonstrating a high‐performance electron transport layer‐free (ETL‐free) PSC. The integrated EMIMPF6 assisted the internal charge collection and favored the interfacial charge transfer from perovskite to FTO substrate, contributing to the high performance of ETL‐free PSCs. The ETL‐free PSCs showed a conversion efficiency of 16.2%, which is comparable with its conventional counterpart. This work provides a solution to simplify the PSC structure and would have an impact on designing a scalable manufacturing process for PSCs. [ABSTRACT FROM AUTHOR]

Hole transport layers (HTLs) play a key role in perovskite solar cells (PSCs), particularly in the inverted PSCs (IPSCs) that demand more in its stability. In this study, samarium‐doped nickel oxide (Sm:NiOx) nanoparticles are synthesized via a chemical precipitation method and deposited as a hole transport layer in the IPSCs. Sm3+ doping can reduce the formation energy of Ni vacancy and naturally increase the density of Ni vacancies, thereby rendering increased hole density. Thenceforth, the electronic conductivity is enhanced significantly, and work function enlarged in the Sm:NiOx film in favor of extracting holes and suppressing charge recombination. Consequently, the Sm:NiOx‐based IPSCs attain outstanding power conversion efficiencies as high as 20.71%. Even when it is applied in flexible solar cells, it still outputs efficiency as high as 17.95%. More importantly, the Sm:NiOx is compatible with large‐scale processing whereby the large area IPSCs of 1.0 cm2 and 40 × 40 mm2 deliver high efficiencies of 18.51% and 15.27%, respectively, all are among the highest for the inorganic HTLs based IPSCs. This research demonstrates that, while revealing the doping effect in depth, Sm:NiOx can be a promising hole transport material for fabricating efficient, large‐area, and flexible IPSCs in the future. [ABSTRACT FROM AUTHOR]

With the power conversion efficiencies of perovskite solar cells (PSCs) exceeding 25%, the PSCs are a step closer to initial industrialization. Prior to transferring from laboratory fabrication to industrial manufacturing, issues such as scalability, material cost, and production line compatibility that significantly impact the manufacturing remain to be addressed. Here, breakthroughs on all these fronts are reported. Carbon‐based PSCs with architecture fluorine doped tin oxide (FTO)/electron transport layer/perovskite/carbon, that eliminate the need for the hole transport layer and noble metal electrode, provide ultralow‐cost configuration. This PSC architecture is manufactured using a scalable and industrially compatible electrospray (ES) technique, which enables continuous printing of all the cell layers. The ES deposited electron transport layer and perovskite layer exhibit properties comparable to that of the laboratory‐scale spin coating method. The ES deposited carbon electrode layer exhibits superior conductivity and interfacial microstructure in comparison to films synthesized using the conventional doctor blading technique. As a result, the fully ES printed carbon‐based PSCs show a record 14.41% power conversion efficiency, rivaling the state‐of‐the‐art hole transporter‐free PSCs. These results will immediately have an impact on the scalable production of PSCs. [ABSTRACT FROM AUTHOR]

Inorganic cesium lead halide perovskite solar cells (PSCs) have been widely explored due to their outstanding thermal stability and photovoltaic performance. However, the application and development of CsPbIBr2‐based PSCs is still hindered by major challenges such as high fabrication temperature and large voltage loss. To address these difficulties, additive engineering is conducted using n‐butylammonium iodide (BAI). It is found that it not only improves the crystallization and morphology of perovskite layers but also substantially decreases the annealing temperature. In addition, the BAI incorporation decreases trap state density and restrains nonradiative recombination. As such, a high power conversion efficiency (PCE) of 10.78% is achieved, 21% higher compared with that of the control sample (8.88%). It should be noted that this is particularly high for the CsPbIBr2 PSCs fabricated at low temperatures (<200 °C) that are required for flexible devices based on polymeric substrates. [ABSTRACT FROM AUTHOR]

Herein, a superhydrophobic coating with high transparency and ultrahigh adhesive force was designed and prepared for use on the glass covers of solar cells, which exhibited excellent thermal stability and strong acid–base corrosion resistance. SiO2, as the bottom layer, was prepared via plasma enhanced chemical vapor deposition (PECVD), and then glycidoxypropyltrimethoxysilane (KH560) hydrolysis condensation resulted in the formation of hydroxyl groups at the two ends, which were used to form a network structure as the middle connecting layer. The top superhydrophobic layer was obtained via the hydrophilic modification of SiO2 by hexamethyldisilazane (HMDS). The structure of this superhydrophobic surface is similar to the bilayer structure of the phospholipids in the cell membrane. The superhydrophobic coating exhibited high optical transmittance, which reached 94% in the visible region. The results show that the superhydrophobic coating has an excellent self-cleaning performance (WCA = 153°). Moreover, its surface showed remarkable stability against strong acid, strong alkali, and the impact of water drops and sand. Finally, a simple simulation of silicon-based superhydrophobic glass solar cells was carried out, and a long-term outdoor experiment was performed to test their photoelectric conversion efficiency. During the two-month study period, the power conversion efficiency (PCE) of the solar cell module without the coating was reduced to 13.01% due to the natural deposition of dust, which was significantly lower than that of the superhydrophobic coating-covered module with self-cleaning function (PCE was 14.21%). [ABSTRACT FROM AUTHOR]

A double-layer composite film (DLCF) that consists of upconversion composite La(OH)3:Er3+/Yb3++P25 (UC + P25) as underlayer and large TiO2 spheres (LS-TiO2) as overlayer is designed as the photoelectrode of dye-sensitized solar cells (DSSCs). The upconversion luminescent material La(OH)3:Er3+/Yb3+ can convert near-infrared region to visible light to improve the light absorption, and LS-TiO2 has been used as light-scattering layer to increase the optical length in the film and enhance light harvesting. The DLCF with lower absorbed dye achieved the highest conversion efficiency due to the synergistic effect of the upconversion luminescent layer and the light-scattering layer, and with an optimum mixing ratio, a conversion efficiency of 9.24% is attained, which is a significant improvement of 68.3% compared with the pure P25 film photoelectrode. [ABSTRACT FROM AUTHOR]

Low Pt-loaded graphene nanocomposites were prepared using a two-step reduction process. Graphene dispersion was first prepared from graphene oxide using hydrazine hydrate as a reducing agent. Pt-reduced graphene oxide composites were then synthesized in the aqueous graphene dispersion at 90 °C without the need for another reductant. Pt/graphene composite films were then deposited on fluorine-doped tin oxide substrates using a simple drop-casting method at room temperature and subsequently used as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Cyclic voltammetry and electrical impedance analysis show that the composite electrodes have high electrocatalytic activity toward iodide/triiodide reduction. The energy conversion efficiency of the Pt/graphene CE-based DSSC was found to be 1.9 % lower than that of cells with a Pt-based CE. [ABSTRACT FROM AUTHOR]

Preparation of graphene composite material suitable for drop-coating on FTO conductive glasses in ambient conditions is reported. Highly dispersed PEDOT:PSS/graphene composites were synthesized by in situ polymerization of 3,4-ethylenedioxythiophene (EDOT) using aqueous graphene dispersions as a precursor without the need for further reducing steps. The structural properties of the PEDOT:PSS/graphene were investigated by transmission electron microscope and FT-IR spectrometry. Graphene sheets as the support material likely provided increased active sites for the polymerization of EDOT. The graphene sheets were homogeneously coated by PEDOT:PSS. Drop-coating the solution of PEDOT:PSS/graphene nanocomposites onto FTO glass yielded graphene composite counter electrodes (CEs) useful for dye-sensitized solar cells (DSSCs). Both in cyclic voltammetry measurements and electrochemical impedance spectroscopy, the composite CEs exhibited good catalytic activity. The DSSCs based on PEDOT:PSS/graphene CEs showed a conversion efficiency of 4.66 %, comparable to platinum CE-based cells which showed a conversion efficiency of 5.94 %. [ABSTRACT FROM AUTHOR]

Abstract: Graphene films with controllable thicknesses, electrical and optical properties are fabricated on variable substrates at room temperature by a simple, efficient and low-cost solution-based method. This process is completely compatible with flexible substrates (polyethylene terephthalate, PET), fluorine-doped tin oxide (FTO) conductive glasses, and even glassy carbon electrodes. The graphene films show excellent conductivity and electrochemical activity. The films prepared on FTO conductive glasses, as an alternative to ubiquitously employed platinum-based counter electrodes (CEs) for dye-sensitized solar cells (DSSCs), are demonstrated. The results suggest a new start in the direction of graphene CEs for the development of next generation of optoelectronics. [Copyright &y& Elsevier]

It is important to lower the cost and stability of the organic–inorganic hybrid perovskite solar cells (PSCs) for industrial application. The commonly used hole transport materials (HTMs) such as Spiro-OMeTAD, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and poly(3-hexylthiophene-2,5-diyl) (P3HT) are very expensive. Here, 3,4-ethylenedioxythiophene (EDOT) monomers are in-situ polymerized on the surface of graphene oxide (GO) as PEDOT-GO film. Compared to frequently used polystyrene sulfonic acid (PSS), GO avoids the corrosion of the perovskite and the use of H2O solvent. The composite PEDOT-GO film is between carbon pair electrode and perovskite layer as hole transport layer (HTL). The highest power conversion efficiency (PCE) is 14.09%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acetate ion functionalized polar ionic liquid (IL), 1-allyl-3-methylimidazolium acetate (AMIMOAc), has firstly been used not only as an additive in MAPbI 3 perovskite film but also as an interfacial modification layer between SnO 2 and MAPbI 3 in carbon counter electrode-based perovskite solar cells. • The appropriate content of IL can reduce the number of trap states in MAPbI 3 perovskite film to inhibit non-radiative recombination and increase carrier lifetime, further improve the PCE to 15.16%. • The stability of the devices has been improved remarkably. The device with AMIMOAc IL has retained 93% of its initial PCE after storing for 500 h. The potential of perovskite solar cells as a representative alternative to silicon-based solar cells has become significant owing to their unparalleled advancement in efficiency. However, the intrinsic instability of perovskite still hinders their large-scale commercial application, particularly of the decomposition of perovskite during device operation. To address this issue, an acetate-ion-functionalized polar ionic liquid, 1-allyl-3-methylimidazolium acetate (AMIMOAc), is used as an additive in MAPbI 3 film. FTIR spectroscopy measurements show that AMIMOAc can anchor the organic cations via hydrogen bonding and enhance the Pb–O interaction in modified MAPbI 3 , leading to a continuous and dense morphology to increase the stability of MAPbI 3. After optimizing the concentration of AMIMOAc, an additional interfacial modification layer accelerates the electron extraction and transport. By the synergy of both additive engineering and interface modification, the device not only achieves a high efficiency of 15.16%, but also maintains 93% of the initial PCE after 500 h, showing significantly improved stability. These results pave the way to a new strategy to improve efficiency and long-term stability of carbon counter electrode-based PSCs. [ABSTRACT FROM AUTHOR]

Hole-conductor-free carbon-based perovskite solar cells (C-PSCs) are known for their low-cost and superstability. In this work, different mesoporous structures, namely, mesoporous TiO 2 + Al 2 O 3 (mp-TiO 2 + Al 2 O 3), mp-TiO 2 + ZrO 2 , mp-Al 2 O 3 , mp-TiO 2 , and blocking compact layer of TiO 2 (bl-TiO 2), were investigated and systematically compared. Results revealed that the performance of PSCs with double-layer mesoporous structure was better than that of the other mesoporous structures, especially PSC with the structure of mp-TiO 2 + Al 2 O 3 obtained the open-circuit voltage (V oc) of 0.97 V and the current density (J sc) of 23.77 mA cm−2, respectively, the photoelectric conversion efficiency (PCE) reached 11.3% because of the function of the mesoporous layer in separating TiO 2 and carbon, thereby avoiding direct contact and reducing the leakage of the current. Al 2 O 3 and ZrO 2 are insulating materials that could effectively prevent electrons from transmitting back to C. The mesoporous structure of the device based on mp-TiO 2 + Al 2 O 3 was evenly distributed, the perovskite crystal particles based on mp-TiO 2 + Al 2 O 3 were enlarged, uniform, and relatively tight, and the grain boundaries between the perovskite crystal particles were remarkably reduced. Among the films, the perovskite film of mp-TiO 2 + Al 2 O 3 structure had the highest absorption intensity. This study provided a new basis for commercializing low-cost PSCs. • Mesoporous layer promotes perovskite film formation and separates TiO 2 and C. • Insulating material prevents the electrons from transmitting back to C. • Device with mesoporous TiO 2 + Al 2 O 3 obtained the best efficiency of 11.3%. [ABSTRACT FROM AUTHOR]

Hole-transport-layer-free organic-inorganic halide perovskite solar cells are attracted wide attention due to low cost, good reproducibility and long-time stability. However, this type of perovskite solar cell still requires the high process temperature beyond 400 °C. Here, the planar perovskite solar cells with the structure of glass-FTO/ZnO/perovskite/Carbon are successfully fabricated at low temperature. The pristine CH 3 NH 3 PbI 3 device exhibits the current density of 19.91 mA cm−2 and a power conversion efficiency of 12.81%. Meaningfully, when ammonium chloride is added to the solution of iodide methylamine, the current density and power conversion efficiency of the resulting device can be improved to 20.21 mA cm−2 and 13.62%, respectively. The high performances of device are mainly attributed to compact and smooth surface of perovskite film due to NH 4 Cl additive. More importantly, the cells also demonstrate good reproducibility, good illumination stability and good long-time stability. The unencapsulated cells can maintain over 90% of the initial power conversion efficiency at 25–28 °C in an ambient environment with 45–60% humidity over 1200 h. The present study can provide a facile and low cost approach to fabricate highly efficient and highly stable perovskite solar cells for the future application. Image 1 • Hole-transport-layer-free perovskite solar cell with carbon electrode is fabricated. • The whole fabrication process of devices is under low temperature. • An additive of NH 4 Cl is introduced to improve the quality of MAPbI 3 film. • The champion device shows the high power conversion efficiency of 13.26%. [ABSTRACT FROM AUTHOR]

This work demonstrates the fabrication of a high-efficiency, hole-conductor-free, solid-state perovskite solar cell with TiO 2 -nanorod arrays (NRAs) as photoanodes and commercial carbon ink as counter-electrodes. TiO 2 -NRA films of various thicknesses were deposited on FTO electrodes through hydrothermal method for different reaction durations. The effect of the thickness of TiO 2 -NRA films on device performance was investigated in detail. The TiO 2 NRAs/CH 3 NH 3 PbI 3 /C devices based on 688 nm-thick TiO 2 -NRA films exhibited the optimal performance and power conversion efficiency (PCE) of as high as 8.56%. This value is comparable with the PCE of the recently reported TiO 2 NRA/Perovskite/HTM/Au solar cell. [ABSTRACT FROM AUTHOR]

In this work, perovskite solar cells (PSCs) were fabricated in the ambient air, with a scaffold layer composed of TiO 2 /ZrO 2 double layer as the mesoscopic layer and carbon as the counter electrode. The effect of ZrO 2 thin film thickness on the photovoltaic performances of PSCs was also studied in detail. Results showed that the photoelectric properties of as-prepared PSCs largely depend on the thin film thickness due to a series of factors, including surface roughness, charge transport resistance, and electron-hole recombination rate. The power conversion efficiency of PSCs increased from 8.37% to 11.33% by varying the thin film thickness from 75 nm to 305 nm, and the optimal power conversion efficiency was realized up to the 11.33% with a thin film thickness of 167 nm. This research demonstrates a promising route for the high-efficiency and low-cost photovoltaic technology. [ABSTRACT FROM AUTHOR]

The organic–inorganic perovskite compound (CH 3 NH 3 ) 3 Bi 2 I 9 (MBI) has lower toxicity and higher stability than lead-based perovskite. In this work, we fabricated MBI perovskite-based solar cells (PSCs) through a two-step sequential-solution process by using rutile TiO 2 nanorod array (NRA) films as the electron transporting layer (ETL) for the first time. The thickness, roughness, and crystal structure of the rutile TiO 2 NRAs prepared by hydrothermal method with different reaction times were thoroughly characterized and correlated with the photovoltaic performance of PSCs. Results of morphological and structural analyses, as well as time-resolved photoluminescence studies, indicated the effect of TiO 2 NRA film thickness on the carrier recombination and photovoltaic performance of MBI-based PSCs. The MBI-based device was also stable in an environment with >50% humidity for more than 67 days. [ABSTRACT FROM AUTHOR]

ABX 3 -type organic lead halide perovskites have gained increasing attention as light harvester for solar cells due to their high power conversion efficiency (PCE). Recently, it has become a trend to avoid the use of expensive hole-transport materials (HTMs) and precious metals, such as Au, to be competitive in future commercial development. In this study, we fabricated mixed-cation perovskite-based solar cells through one-step spin-coating using methylammonium (CH 3 NH 3 + ) and formamidinium (HN = CHNH 3 + ) cations to extend the optical absorption range into the red region and enhance the utilization of solar light. The synthesized hole-conductor-free cells with carbon electrode and mixed cations exhibited increased short-circuit current, outperforming the cells prepared with pure methylammonium, and PCE of 10.55%. This paper proposes an efficient approach for fabricating high-performance and low-cost perovskite solar cells. [ABSTRACT FROM AUTHOR]

Defects at the surface and grain boundaries of three-dimensional (3D) organic-inorganic metal halide perovskite films lead to the non-radiative recombination of charge carriers and accelerate perovskite decomposition. In turn, this deteriorates the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Herein, p -methylphenylmethylammonium iodide (p -MePMAI) was reacted with a 3D perovskite to in - situ form a two-dimensional (2D) perovskite upper layer. This upper layer passivated the surface and grain boundary defects of the 3D perovskite film, improving its surface hydrophobicity. As a result, a carbon counter electrode (CE)-based 2D/3D PSC achieved a maximum PCE of up to 15.63%, which was much higher than that of an unmodified 3D MAPbI 3 PSC (12.16%). Moreover, the unencapsulated 2D/3D device maintained 80% of its initial PCE after exposure to air for 700 h with a relative humidity (RH) of 40 ± 5%. This research opens a new pathway for the successful construction of stable and efficient 2D/3D PSCs with organic ammonium salts. [Display omitted] • The p -MePMAI treatment can effectively passivate surface/interface defects and improve the performance of PSCs. • The champion device has a PCE of 15.63% with J sc of 22.15 mA cm−2, V oc of 1.101 V, and FF of 0.64. • The 2D hybrid passivation layer can further increase the stability by preventing contact of water with the 3D perovskite. [ABSTRACT FROM AUTHOR]

[Display omitted] • This review summarizes the application of rare earth material in solar cells. • The rare earth material application of perovskite solar cells is introduced. • The rare earth material improvement of solar cell is discussed. Organic-inorganic lead halide based perovskite solar cell has received broad interest due to their merits of low cost, a low temperature solution process, and high power conversion efficiency. Rare earth ion doped nanomaterials can be used in perovskite solar cell to expand the range of absorption spectra and improve the stability due to its up conversion and down conversion effect. This article reviews recently progress in using rare earth ion doped nanomaterials in mesoporous electrodes, perovskite active layers, and as an external function layer of perovskite solar cell. Finally, we discuss the challenges facing the effective use of rare earth ion doped nanomaterials in perovskite solar cell and present some prospects for future research. [ABSTRACT FROM AUTHOR]

Interface modification g-C 3 N 4 nanosheets to perovskite solar cells. [Display omitted] • Graphitic carbon nitride (g-C 3 N 4) nanosheets were successfully prepared. • g-C 3 N 4 nanosheets were modified on the electron transport layer (ETL) interface. • g-C 3 N 4 nanosheets can effectively coordinate the unreacted lead ions to reduce the bulk defects of the perovskite layer. • An effective strategy to improve the efficiency of device by optimizing the crystal quality of perovskite film. • The efficiency of device was making synergistic efforts to improve from 9.55% to 11.37%. The passivation strategy is considered to be one of the most effective methods to suppress the non-radiative recombination of perovskite solar cells (PSCs), resulting in excellent photovoltaic performance. Herein, it reported a valid strategy to enhance the photoconversion efficiency (PCE) of PSCs by modifying graphitic carbon nitride (g-C 3 N 4) nanosheets into an electron transport layer interface. It is able to optimize surface morphology and crystal quality of perovskite film, which makes synergistic efforts to improve the PCE from 9.55% to 11.37% with these devices. [ABSTRACT FROM AUTHOR]

SnO 2 has attracted extensive attention in planar perovskite solar cells (PSCs) owing to its outstanding photoelectric properties and low temperature preparation. However, pinholes are easy to appear in the annealing process of SnO 2 films, which limits its application in planar PSCs. Here lists a simple and low-cost method: Urea-complexed tin oxide in deionized water can effectively control the concentration of SnO 2. This process is conducive to forming a compact surface morphology. Meanwhile, the work explored the effect of the properties of PSCs with different thicknesses of SnO 2 layers. The system analysis showed that PSCs based on 60 nm SnO 2 layer and the methamphetamine lead iodide (MAPbI 3) light absorber yielded the highest power conversion efficiency (PCE) over 18%, a fill factor (FF) of 0.793, and good stability. Therefore, we believe our study provides an effective way for preparing electron transport layers. [ABSTRACT FROM AUTHOR]

Methylammonium bismuth iodide ((CH 3 NH 3) 3 Bi 2 I 9 , MBI) is a promising alternative to perovskite solar cells (PSCs) due to its air stability and low-toxicity. Herein, a two-stage electric-field-assisted reactive deposition method has been introduced to prepare MBI films for the first time. PSCs based on MBI films were fabricated and characterized. The influences of electric parameters (applied voltage mode, pulse and time, etc.) on the morphology and crystal structure of MBI film correlated with the photovoltaic performance of PSCs have also been investigated systematically in detail. Through adjusting the voltage mode, crystal growth can be completely controlled, leading to a compact MBI film with large grain size. Moreover, the MBI film prepared by electrochemical deposition required no annealing. This work determined that the optimal performance of PSCs is based on the MBI film deposited by square-wave (AC) voltage mode (−7.3 V/+1 V, 5 Hz, 5 min). All devices exhibited long-term stability in ambient air (humidity of >50%) for more than 300 h. This study will inspire further research on the application of electrochemical deposition technique for other lead-free PSCs. Image 1 • A two-stage electric-field-assisted reactive deposition method has been introduced to prepare (CH 3 NH 3) 3 Bi 2 I 9 films for the first time. • The influences of electric parameters on MBI film morphology and crystal structure correlating with the photovoltaic performance of PSCs have been investigated systematically. • The proposed electrochemical deposition method is facile, controllable, and repeatable, and significant to the commercial production of perovskite. • The proposed electrochemical deposition involves an annealing-free fabrication, thus simplifying the process and promoting production efficiency. [ABSTRACT FROM AUTHOR]