CH3NH3PbI3 Perovskite Solar Cells Research Articles

Effects of neodymium or ytterbium addition to CH3NH3PbI3 perovskite solar cells inserted with decaphenylcyclopentasilane

Perovskite solar cells have attained high photoconversion efficiencies by changing chemical compositions of the perovskites and layered structures of the devices. However, the perovskite compounds easily decompose in air atmosphere even at the room temperature, and the photovoltaic properties are degraded by the formed defects. The motivation of this work is to solve these instability problems, and the objective the present work is to improve the film quality of the perovskite compounds by introducing lanthanide elements and decaphenylcyclopentasilane (DPPS), which were expected to contribute to decrease of the defects by the passivation effects. Here, effects of neodymium trifluoride (NdF3) or ytterbium trifluoride (YbF3) addition to CH3NH3PbI3 perovskite solar cells inserted with DPPS were investigated. Introduction of NdF3 or YbF3 increased the lattice constants and promoted crystal growth of the perovskites, and surface treatment by DPPS suppressed the PbI2 formation as surface passivation. Combined additions of NdF3 or YbF3 and DPPS contributed to the improvement of both the conversion efficiencies of the present perovskite devices and the stabilities of the photovoltaic properties by inhibiting the decomposition.

Effects of guanidinium iodide surface treatment on CH3NH3PbI3 perovskite solar cells with added decaphenylcyclopentasilane

The effects of guanidinium iodide surface treatment (GST) on CH3NH3PbI3 perovskite solar cells with decaphenylcyclopentasilane (DPPS) were investigated. GST decreases the carrier trap density and improves the photovoltaic characteristics. The X-ray diffraction results showed that the lattice constants of the perovskite crystals were increased by the insertion of GST and guanidinium into the methylammonium defects. The thermal stability of the unlaminated devices was tested in the air at 85 °C. The device prepared using GST exhibited the highest conversion efficiency. First-principles calculations supported these experimental results.

Effects of ethylammonium and rubidium addition to guanidinium-based CH3NH3PbI3 perovskite photovoltaic devices prepared at 190 °C in ambient air

Effects of the addition of rubidium (Rb) and ethylammonium (CH3CH2NH3, EA) to guanidinium [C(NH2)3, GA]-based CH3NH3PbI3 perovskite solar cells were investigated. Lattice constants and the (100)-orientation of EA- and Rb-modified perovskite crystals increased compared with those of as-prepared perovskite. Abnormal increases of lattice constants of the GA- and EA-modified perovskite crystals prepared at 190 °C for 10 min in ambient air were also observed during the room temperature aging, which was due to crystal growth of the perovskites, and these features contributed to increased conversion efficiencies of devices based on the modified perovskites. Addition of GA and EA also effectively improved the photovoltaic properties of the device under indoor light conditions using white light-emitting diodes. First-principles calculations of the density of states and band structures indicated a reduction of the total energy through the addition of Rb or EA, suggesting that the current density was improved by the reduced band gap.

Wrapped quantum Dot/PBDT-TIPS-DTNT-DT nanostructures in high-level perovskite photovoltaics

ABSTRACT Graphene quantum dot (GQD) and carbon quantum dot (CQD) nanoparticles and their supramolecules, including wrapped poly[bis(triiso-propylsilylethynyl) benzodithiophene-bis(decyltetradecyl-thien) naphthobisthiadiazole] (PBDT-TIPS-DTNT-DT)/GQD and wrapped PBDT-TIPS-DTNT-DT/CQD nanostructures, were prepared and employed in CH3NH3PbI3 perovskite solar cells. All positive features of wrapped nano-hybrids had a synergetic effect on photovoltaic features. Owing to more mature configuration of GQD-based wrapped supramolecules, somewhat better results were obtained compared to CQD-based nanoparticles. The highest short circuit current density (Jsc), fill factor (FF), open circuit voltage (Voc) and, consequently, power conversion efficiency (PCE) parameters were acquired for perovskite + wrapped PBDT-TIPS-DTNT-DT/GQD solar cells (20.13 mA/cm2, 73%, 0.94 V and 13.81%).

Effects of Co-Addition of Guanidinium and Cesium to CH3NH3PbI3 Perovskite Solar Cells

The effects of guanidinium (C(NH2)3, GA) and cesium (Cs) co-additions on methylammonium lead iodide (CH3NH3PbI3, MAPbI3) perovskite solar cells were investigated. The first-principles calculations on the density of the states and band structures showed a reduction in the total energy by the GA addition. Although the calculation showed that the co-addition of the GA/Cs to the MAPbI3 perovskite could decrease the carrier mobilities, and the addition of GA/Cs improved the device performance. This result would be due to a facilitation of grain growth and a suppression of the defects from the GA/Cs addition. The changes to the conversion efficiencies of the device with the best performance were small, which indicates that the present co-addition of GA/Cs is effective for the stability of the devices.

Performance research of perovskite solar cell with light conversion electron transport layer utilizing prism scattered lights

TiO2 conversion luminescent materials doped with Er3+ and Yb3+ are used as electron transport layer to enhance photoelectric performance of CH3NH3PbI3 perovskite solar cells (MAPbI3 PSC) under scattered solar light irradiation by prism. The composition, morphology and optical property of the films were characterized by XRD, XPS, SEM, UV–vis and PL. The up-conversion TiO2 luminescent film absorbs multiple low energy infrared photons and converts them into one visible photon, while the down-conversion TiO2 luminescent film absorbs one high-energy ultraviolet photon and converts it into multiple visible photons. The obtained visible photons can effectively excite the MAPbI3 perovskite to produce more photo-generated electron-hole pairs, thus improving the incident light utilization and power conversion efficiency (PCE) of MAPbI3 PSC. The MAPbI3 PSC with up-conversion TiO2, TiO2 and down-conversion TiO2 electron transport layer (UTD-MAPbI3 PSC) can effectively utilize the infrared, visible and ultraviolet lights obtained from the sunlight dispersed by a prism, respectively. Under the scattered solar light irradiation, the PCE of UTD-MAPbI3 PSC is increased by 11.22%, compared with that of the MAPbI3 PSC with un-doped TiO2 as the electron transport layer (TiO2-MAPbI3 PSC). This may provide a new idea to enhance the utilization ratio of sunlight for solar cells.

Metallophtalocyanine Used Interface Engineering for Improving Long‐Term Stability of Methylammonium Lead Triiodide Perovskite

CH3NH3PbI3 perovskite solar cells using metal phthalocyanines (MPcs) with decaphenylcyclopentasilane (DPPS) are fabricated and characterized. The effect of addition of MPcs on the photovoltaic properties is investigated by changing the central element of the MPc and depositing MPc and DPPS successively on the perovskite layer. When silicon phthalocyanine is used to the cell, the microstructure of the perovskite film improves, which results in improvement of the open‐circuit voltage, fill factor, and photoconversion efficiency. For cells with only MPcs as the hole‐transport layer, the conversion efficiency increases by passivation with the phthalocyanine and crystal growth at room temperature.

Enhanced performance of inverted hybrid perovskite solar cells with interfacial passivation filler

Defects at the interface between the perovskite and charge transport layers in perovskite solar cells serve as sites for non-radiative charge recombination as they are the main energy loss channels that reduce the open-circuit voltage. In this study, we used a small molecule, N-methyl-4-piperidone (NMPD), as an interfacial passivation filler between the perovskite and electron transport layers in inverted organic–inorganic hybrid CH3NH3PbI3 perovskite solar cells. The filler deactivates the charge traps at the interface, which are responsible for non-radiative charge recombination, and improves the electron extraction efficiency. Consequently, it enhanced the power conversion efficiency (PCE) from 16.3% to 20.1% by increasing both the open-circuit voltage and short-circuit current. Furthermore, after 800 h of aging without encapsulation at 35% humidity and 25 °C temperature, the device with NMPD filler retained 78.4% of the initial PCE. This indicates that the interfacial modification filler, with a single carbonyl group, can effectively improve the efficiency as well as the stability of perovskite devices.

Direct Tracking of Charge Carrier Drift and Extraction from Perovskite Solar Cells by Means of Transient Electroabsorption Spectroscopy.

The best perovskite solar cells currently demonstrate more than 25% efficiencies, yet many fundamental processes that determine the operation of these devices are still not fully understood. In particular, even though the device performance strongly depends on charge carrier transport across the perovskite layer to selective electrodes, information about this process is still very controversial. Here, we investigate charge carrier motion and extraction from an archetypical CH3NH3PbI3 (MAPI) perovskite solar cell. We use the ultrafast electric-field-modulated transient absorption technique, which allows us to evaluate the electric field dynamics from the time-resolved electroabsorption spectra and to visualize the motion of charge carriers with subpicosecond time resolution. We demonstrate that photogenerated holes drift across the mesoporous TiO2/perovskite layer during hundreds of picoseconds. On the other hand, their extraction into the spiro-OMeTAD hole transporting layer lasts for more than 1 nanosecond, suggesting that the hole extraction is limited by the perovskite/spiro-OMeTAD interface rather than by the hole transport through the perovskite layer. Additionally, we use the ultrafast time-resolved fluorescence technique that reveals fluorescence decay during tens of picoseconds, which we attribute to the spatial separation of electrons and holes.

Study on light absorption of CH3NH3PbI3 perovskite solar cells enhanced by gold nanobipyramids

Perovskite solar cell is a third-generation solar cell with great potential. A method for reducing light energy loss and enhancing light absorption without changing the thickness of perovskite layer need to be developed urgently. In this paper, the gold nanobipyramids were applied in CH3NH3PbI3 perovskite solar cells, and their light absorption enhancement efficiency was calculated using the finite difference time domain method. The results show that the plasmon effect of gold nanobipyramids can significantly enhance the light absorption efficiency of the absorption layer with an increase of 45.48%. Further studies show that gold nanobipyramid arrays with different depths and layers remarkably influence the improvement of light absorption efficiency of the perovskite solar cells. The mechanism was verified by calculating the electric field enhancement and light reflectivity. Finally, an optimization scheme of gold nanobipyramid arrangement in perovskite layer was discussed. This study provides a new idea for enhancing the light absorption capacity and improving the photoelectric conversion efficiency of perovskite solar cells. This method has potential applications in other solar cells.

Cutting-edge stability in perovskite solar cells through quantum dot-covered P3HT nanofibers

ABSTRACT Graphene and carbon quantum dot (GQD and CQD) nanoparticles as well as their related supramolecules, entitled as poly(3-hexylthiophene) (P3HT) nanofiber NF/GQD and P3HT NF/CQD, were prepared via decoration of QDs onto P3HT nanofibers, and applied in CH3NH3PbI3 perovskite solar cells. CH3NH3PbI3 photovoltaic cells represented performance of 10.61%, but completely lost function after 150 days air exposure. Instead, P3HT NF/QD supramolecules considerably promoted and stabilized perovskite photovoltaics. Efficacies of (20.15 and 18.90%) and (12.73 and 10.96%) were reached within 0 and 150 days exposure to air at 30°C and 35% humidity for P3HT NF/GQD and P3HT NF/CQD modified devices, respectively.

Simulation study of significant optical absorption enhancement for “n-i-p” structured perovskite solar cells with optimized periodic nano texture

We report a significant enhancement of the ultimate efficiency, η, of CH3NH3PbI3 (abbr.: MAPbI3) perovskite solar cells (PSCs) with optimized periodic poly(methyl methacrylate) (PMMA) nano texture, owing to the light trapping effect. With the finite difference time domain (FDTD) simulations, we investigated the η of the nano-textured PSCs (NT-PSCs) when the MAPbI3 layer thickness, dp, ranges from 31.25 nm to 2 μm. The optimized ultimate efficiency, ηm, is defined as the η optimized over the geometric parameters of the nano texture. When dp is approximately 125–500 nm, compared with that of the planar ones, ηm of the PSCs with optimized nano texture is significantly improved by ca. 11.5%–32.8%. Notably, when dp is 125 nm, ηm of the optimized NT-PSCs achieves 24.3%, which is relatively 32.8% larger than that of the planar PSCs. It is very potential to fabricate optimized PMMA nano texture in PSCs to enhance their PCE.

Revealing fundamentals of charge extraction in photovoltaic devices through potentiostatic photoluminescence imaging

Revealing fundamentals of charge extraction in photovoltaic devices through potentiostatic photoluminescence imaging

Effects of Cu, K and Guanidinium Addition to CH3NH3PbI3 Perovskite Solar Cells

Effects of Cu, K and Guanidinium Addition to CH3NH3PbI3 Perovskite Solar Cells

Additive effect of lanthanide compounds into perovskite layer on photovoltaic properties and electronic structures

Fabrication and characterization of lanthanide compound doped CH3NH3PbI3 (MAPbI3) perovskite solar cells have been performed for improving the photovoltaic properties with long-term stabilities of conversion efficiency. The purpose of this research is to investigate additive effect of formamidinium iodine (FAI) and lanthanide compound into the perovskite layer for improving carrier diffusion and mobility in the perovskite layer. Incorporation of FAI and europium chloride (EuCl2) into the perovskite crystals maintained the stability of conversion efficiency for 30 days. The photovoltaic properties were based on the crystal growth and orientation with suppression of decomposition, thermodynamic stabilities, and the narrow band dispersion with decrease of effective mass. In contrast case, addition of samarium or terbium compound reduced the stabilities, and suppressed the carrier mobility owing to the flat band dispersion of localized d orbital of samarium atom or 4 f orbital of terbium atom near valence band state. The annealing treatment improved the crystal orientation related to the carrier diffusion with inhibiting recombination, improving short circuit current density and external quantum efficiency. The perovskite crystal doped with EuCl2 and FAI have high advantage to apply for practical use of the photovoltaic devices with long-term stability.

Fabrication and characterization of CH3NH3PbI3 solar cells with added guanidinium and inserted with decaphenylpentasilane

In this work we investigated the effects of the addition of guanidinium [C(NH2)3; GA] on CH3NH3PbI3 perovskite solar cells fabricated at a high temperature of 190°C in atmospheric air. The addition of GA iodide and the insertion of decaphenylpentasilane between the perovskite and hole transport layer improved the external quantum efficiency and short-circuit current density, and the conversion efficiencies were stable after 1 month. X-ray diffraction showed that the lattice constant of the perovskite crystals was increased by the addition of GA, and addition of GA also improved the surface morphology. First-principles calculations on the density of states and band structures showed reduction of the total energy by the addition of GA and the effectiveness of the nitrogen atoms in GA.

Oxidized Nickel to Prepare an Inorganic Hole Transport Layer for High-Efficiency and Stability of CH3NH3PbI3 Perovskite Solar Cells

In this study, we report a perovskite solar cell (PSC) can be benefited from the high quality of inorganic nickel oxide (NiOx) as a hole transport layer (HTL) film fabricated from the physical vapor deposition (PVD) process. The power conversion efficiency (PCE) of PSC is found to depend on the thickness of NiOx HTL. The NiOx thickness is optimized via quantitative investigation of the structure, optical and electrical properties. With an active area of 11.25 cm2, a PSC module (25 cm2) with a PCE of 15.1% is demonstrated, while statistically averaged PCE = 18.30% with an open voltage (Voc) 1.05 V, short-circuit current density (Jsc) 23.89 mA/cm2, and fill factor (FF) 72.87% can be achieved from 36 devices with smaller active areas of 0.16 cm2. After the stability test at 40% relative humidity (RH) and 25 °C for 1200 h, the highest performance NiOx-based PSC is shown to be about 1.2–1.8 times superior to PEDOT:PSS organic HTL based PSC at the same environment.

Electronic structure of Li+@C60 adsorbed on methyl-ammonium lead iodide perovskite CH3NH3PbI3 surfaces

Jeon et al. [Angew. Chem., 2018, 57, 4607] showed that air stability for over 1000 hours under light illumination can be achieved in CH3NH3PbI3 perovskite solar cells when Li+ is replaced by Li+@C60 in a dopant material used in the p-type donor layer.

Moisture Stability of Perovskite Solar Cells Processed in Supercritical Carbon Dioxide.

Performance degradation under environmental conditions currently limits the practical utility of perovskite-based solar cells. The moisture stability of CH3NH3PbI3 perovskite films and solar cells was measured during exposure to three different levels of relative humidity. The films were crystallized at two different temperatures with and without simultaneous exposure to supercritical carbon dioxide. The film crystallinity, optical absorption, and device photoconversion efficiency was measured over time for three relative humidity levels and both crystallization methods. It was determined that film crystallization in supercritical CO2 resulted in significant improvement in moisture stability for films processed at 50 °C, but negligible improvement in stability for films processed at 100 °C.

A methylammonium iodide healing method for CH3NH3PbI3 perovskite solar cells with high fill factor over 80%

Repressing the thermal decomposition during the process of heat treatment plays an indispensable part in the preparation of perovskite films. Here, a methylammonium iodide healing method was applied to prevent the volatilization of the organic component inside the perovskite structure during the heat treatment. High-quality CH3NH3PbI3 film with a much larger grain size over 800 nm was successfully fabricated via this healing method. Besides, the absorption and photoluminescence intensity were also both improved. Finally, the best power conversion efficiency of 18.89% with a fill factor over 80% was realized in an n–i–p configuration while possessing outstanding stability. This work suggests that methylammonium iodide healing method is a reliable way to promote crystal growth and improve the photovoltaic performance and humidity stability of the CH3NH3PbI3 solar cells.