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The addition of copper bromide to the perovskite precursor solutions increased the conversion efficiencies of the devices. On the other hand, the short-circuit current densities decreased with an increase in the added amounts of copper (Cu). From first-principles calculations, the partial substitution of lead with Cu resulted in the formation of a Cu d orbital energy level in the forbidden band, which worked as a recombination center, causing the generated carriers to disappear. Experiments and calculations show the effects of Cu substitution on the electronic structures and the ability of the addition of Cu compounds to further improve the device performance. [ABSTRACT FROM AUTHOR]

First-principle calculation analysis on electronic structures and molecular dynamics was performed to investigate the addition of gadolinium ion into a formamidinium lead iodine (FAPbI3) perovskite crystal for use in the application of photovoltaic devices with stability of performance. Band dispersion, density of state, enthalpy, and kinetic energy were predicted during the relaxation process. The Gd2+-doped FAPbI3 perovskite crystal had an effective mass ratio of 0.02 in narrow band dispersion, consisting of 5d and 4f orbitals of gadolinium ion, a 6p orbital of lead ion, and a 5p orbital of iodine ion, supporting the charge transfer and carrier diffusion related to carrier mobility as a photovoltaic parameter. The molecular dynamics of the Gd2+-doped perovskite crystal indicate dynamic stability while suppressing decomposition, with separation between nitrogen and hydrogen ions on FA in the crystal. The first-principle calculation predicts that it is advantageous to apply the Gd2+-doped FAPbI3 perovskite crystal to the perovskite solar cell, providing stability of photovoltaic performance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

CH3NH3PbI3 perovskite compounds are unstable in air due to the migration of CH3NH3. The purpose of the present work is to investigate the effects of addition of guanidinium C(NH2)3 (GA) and cesium (Cs) on CH3NH3PbI3 perovskite solar cells. The addition of GA/Cs 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. First-principles calculations on the density of states and band structures showed reduction in the total energy by the GA addition. [ABSTRACT FROM AUTHOR]

Copper, alkali metals, and organic cations were added to perovskite precursor solutions to enhance the photovoltaic conversion properties and durability of perovskite solar cells. Device properties were improved by the co-addition of copper and sodium. The enhancement of open-circuit voltage by bromine substitution also contributed to the improvement of conversion efficiency. First-principles calculations indicated that the energy levels derived from the Cu d orbital would function as an acceptor level. While the conversion efficiency of the device increased, the durability of the device decreased. Considering the results of the first-principles calculation, the decrease in device durability was attributed to the instability of the crystal structure due to the Cu and sodium substitutions. To enhance the crystal stability, ethylammonium was introduced as a stable organic cation, and the addition of ethylammonium to the perovskite precursor solution significantly enhanced the device's durability while maintaining conversion efficiency. [ABSTRACT FROM AUTHOR]

In this study, the stabilities and conversion efficiencies of perovskite solar cells including cesium (Cs) or formamidinium (FA) at the CH₃NH₃ site were investigated. The additive effects on the photovoltaic properties and crystalline structures were investigated via current–voltage measurements, X-ray diffraction, and scanning electron microscopy. The simultaneous co-addition of Cs and FA to the CH3NH3PbI3 perovskite crystal improved the photovoltaic properties, which may be due to the suppression of the decomposition of the perovskite crystals and the promotion of crystal growth. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskite solar cells have the advantage of being able to implement a high conversion efficiency, easy fabrication process and low cost to commercial products of photovoltaic devices. The perovskite solar cells have a photovoltaic performance with reduced durability due to the volatility of organic cations and toxic lead in the perovskite crystal as an active layer. The purpose of this research is to investigate the effect of additives such as cupper chloride and potassium iodide in the perovskite crystal on the photovoltaic properties and electronic structure. The distribution of 3d orbital of cupper ion conjugated with 5p orbital of iodine ion at the valence band, and 6p orbital of lead ion at the conduction band, influences the charge generation and transfer, as well as the carrier mobility with a narrowing band gap. The addition of potassium iodide delocalizes the charge distribution near the cupper, iodide, and lead ions, which promotes the charge generation and carrier diffusion, yielding an increase in the short circuit current density relating to the conversion efficiency. [ABSTRACT FROM AUTHOR]

Perovskite photovoltaic devices added with tin (Sn) dichloride and copper (Cu) bromide were fabricated and characterized. The thin film devices were prepared by an ordinary spin-coating technique using an air blowing method in ambient air. A decaphenylcyclopentasilane layer was coated at the surface of perovskite layer and annealed at a high temperature of 190 °C. Conversion efficiencies and short-circuit current densities were improved for devices added with Sn and Cu compared with the standard devices. The energy gap of the perovskite crystal decreased through the Sn addition, which was also confirmed by first-principles calculations. [ABSTRACT FROM AUTHOR]

Perovskite solutions with added potassium iodide (KI) and ethylammonium bromide (EABr) were used to fabricate perovskite solar cells in ordinary air at 190 °C. The addition of EABr and KI induced (100)-oriented perovskite crystals, which resulted in the improvement in short-circuit current densities and conversion efficiencies. The short-circuit current density, open circuit voltage, and conversion efficiency of the best device were 21.0 mA cm−2, 0.942 V, and 12.88%, respectively. First-principles calculations also indicated a decrease in total energy per cell and an increase in energy gaps, which agreed with the improved results of device stabilities and photovoltaic properties. [ABSTRACT FROM AUTHOR]

In this study, CH3NH3PbI3 perovskite solar cells with added copper (Cu) and potassium (K) or guanidinium (GA) were fabricated and characterized. The effects of the additives on the photovoltaic properties, morphology and crystalline structure were investigated, and the electronic structures and thermodynamic stabilities are discussed. The stability and conversion efficiency of the perovskite solar cell improved by incorporating Cu at the lead site and K or GA at the CH3NH3 organic cation site in the cubic crystal. Simultaneous addition of Cu and K to the perovskite crystal suppressed decomposition of the crystal by desorption of methylammonium (MA), which led to improvement of the stability of the photovoltaic device. After 28 days, the conversion efficiency of the device with co-added Cu and K was still 10.8%, whereas that of the standard device decreased to 10.1%. [ABSTRACT FROM AUTHOR]

First-principles electronic band calculations were used to investigate the effects of alkali metals and organic cations added to Cu-based perovskite solar cells. The copper d-orbital band was slightly above the valence-band maximum and functioned as an acceptor level for carrier generation. Excitation from iodine p-orbitals and copper d-orbitals to alkali metal s-orbitals could suppress carrier recombination and promote carrier transport. Experimental solar conversion efficiencies increased after adding both Cu and Na, in agreement with the calculations. Total-energy calculations indicated that the perovskite crystal stability increased with the addition of ethyl ammonium, although the total energy decreased with the addition of Cu and Na. [ABSTRACT FROM AUTHOR]

Fabrication and characterization of methylammonium lead iodide perovskite solar cells incorporated with methylammonium bromide (MABr), formamidinium bromide (FABr), and decaphenylcyclopentasilane (DPPS) were performed. Additive effect of MABr or FABr into the perovskite layers inserted with DPPS as hole-transporting layer was investigated. Addition of 5% MABr or FABr into the perovskite layer improved the short-circuit current density, shunt resistance, and open-circuit voltages, which depended on the uniform morphologies while suppressing defects and pinholes in the perovskite layer. The stabilities of the photovoltaic performance depended on the degree of incorporation of MABr or FABr with the DPPS layer, which suppressed decomposition in the perovskite layer. [ABSTRACT FROM AUTHOR]

CH3NH3PbI3 (MAPbI3) perovskite solar cells with guanidinium (C(NH2)3+, GA+) are fabricated at 150 °C using 3CH3NH3I:PbCl2 starting composition in ambient atmosphere, and characterized. Their photoconversion efficiencies and stabilities are improved by the addition of a small amount of GA+. Lattice volumes are increased by the addition of GA+, which confirms the occurrence of GA+ substitution at the CH3NH3 site. Energy gaps are decreased by the addition of GA+, which agrees well with the results of molecular orbital calculation and band calculation. The carrier trap density is reduced by the GA+ addition, which suggests that lattice defects are suppressed by the GA+ doping. Two‐year stabilities of the devices in ordinary air are also investigated, which indicate the effectiveness of GA addition. [ABSTRACT FROM AUTHOR]

Ni- and Co-incorporated CH3NH3PbI3 perovskite solar cells were fabricated and characterized to optimize the photovoltaic and optical properties related to surface morphology, crystal growth and orientation, and electronic structures. Partially replacing Pb with Ni or Co in the perovskite crystals improved the photovoltaic performance and carrier mobility based on the effective mass in the band structure. In particular, the addition of both Ni and Rb compounds to perovskite improved the long-term stability of the photovoltaic cells, which depended on surface modification and coverage, crystal growth, and the high (100) orientation in the perovskite layer. The short-circuit current density of the cells was increased by promoting the generation and mobility of photoinduced carriers, which were inversely proportional to the effective mass ratio. Electron correlation was associated with the promotion of charge transfer owing to the hybridization between the 3d orbitals of Ni and the 5p orbitals of the I atoms near the valence band state. [ABSTRACT FROM AUTHOR]

The effects of doping with alkali metals and formamidinium cations on CH3NH3(Rb)Pb(Cu)I3(Cl,Br) perovskite photovoltaic cells were investigated. Lattice constants were slightly decreased and increased by K and Na doping, respectively. This indicated that Na atoms occupied interstitial sites in the perovskite crystal. The conversion efficiencies for most of the devices decreased after one year. However, the conversion efficiency for the CH3NH3(Na,Rb)Pb(Cu)I3(Cl,Br) photovoltaic cell was unchanged after one year. The Na-doped perovskite provided the smallest carrier trap density, which suggested that lattice defects were suppressed by Na doping. First principles calculations supported these experimental results. [ABSTRACT FROM AUTHOR]

Perovskite compound-based solar cells using methylammonium lead iodine (CH3NH3I), lead iodine (PbI2) and formamidinium chloride (HC(NH2)2Cl: FACl) were fabricated and characterized for improving the photovoltaic performance. Additive effects of FACl into the methylammonium-lead-halide perovskite layer on the photovoltaic properties were investigated. The slight additive of FACl into the perovskite layer promoted the crystal nucleation and growth with the monodispersed domain as the surface morphologies, which improved the photovoltaic performance with external quantum efficiency over ultra-violet–visible–near infrared region. The photovoltaic performance was improved by the surface morphology with the monodispersed crystal growth in the homogenous phase for promoting the photo-induced carrier-generation and extension of the carrier diffusion with suppression of the carrier recombination and trapping near pinholes, defects, voids, cracks and interface between the domains in the perovskite layer. [ABSTRACT FROM AUTHOR]

Effects of polysilane additions on CH3NH3PbI3 perovskite solar cells were investigated. Photovoltaic cells were fabricated by a spin-coating method using perovskite precursor solutions with polymethyl phenylsilane, polyphenylsilane, or decaphenyl cyclopentasilane (DPPS), and the microstructures were examined by X-ray diffraction and optical microscopy. Open-circuit voltages were increased by introducing these polysilanes, and short-circuit current density was increased by the DPPS addition, which resulted in the improvement of the photoconversion efficiencies to 10.46%. The incident photon-to-current conversion efficiencies were also increased in the range of 400~750 nm. Microstructure analysis indicated the formation of a dense interfacial structure by grain growth and increase of surface coverage of the perovskite layer with DPPS, and the formation of PbI2 was suppressed, leading to the improvement of photovoltaic properties. [ABSTRACT FROM AUTHOR]

Fabrication and characterization of lanthanide compound doped CH 3 NH 3 PbI 3 (MAPbI 3) 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 (EuCl 2) 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 EuCl 2 and FAI have high advantage to apply for practical use of the photovoltaic devices with long-term stability. [Display omitted] • Addition of FAI and EuCl 2 promoted crystal orientation, improving J sc related to η. • Incorporation of Eu2+ caused thermodynamic stabilities, maintaining η for 30 days. • Substitution of Eu2+ narrowed band dispersion with decrease of effective mass. • Addition of Sm2+ or Tb3+ ion reduced thermodynamic stabilities as decomposition. • Localization of d, f-orbital of Sm2+ or Tb3+ ions suppressed the carrier diffusion. [ABSTRACT FROM AUTHOR]

CH3NH3PbI3 perovskite photovoltaic devices treated with a polysilane layer were fabricated and characterized. Decaphenylcyclopentasilane (DPPS) in chlorobenzene solution was deposited at the surface of the perovskite layer, and the resulting device was annealed at 140–260 °C. The photoconversion efficiencies of the DPPS-treated device remained high even after 255 days in ambient air. Raman scattering spectroscopy and ab initio molecular orbital calculations of DPPS suggested that it increased hole transport efficiency in the treated devices, which was confirmed from the high shunt resistances of the DPPS-treated devices. [ABSTRACT FROM AUTHOR]

Polysilane-inserted CH3NH3PbI3 perovskite photovoltaic devices combined with potassium and formamidinium iodides were fabricated and characterized. Decaphenylcyclopentasilane layers were inserted at the perovskite/hole transport interface and annealed across a temperature range of 180–220 °C. These polysilane-coated cells prevented PbI2 formation, and the conversion efficiencies were improved over extended periods of time. [ABSTRACT FROM AUTHOR]

Photovoltaic characteristics of solar cell devices in which ethylammonium (EA) and formamidinium (FA) were added to CH3NH3PbI3 perovskite photoactive layers were investigated. The thin films for the devices were deposited by an ordinary spin-coating technique in ambient air, and the X-ray diffraction analysis revealed changes of the lattice constants, crystallite sizes and crystal orientations. By adding FA and EA, surface defects of the perovskite layer decreased, and the photoelectric parameters were improved. In addition, the highly (100) crystal orientations and device stabilities were improved by the EA and FA addition. [ABSTRACT FROM AUTHOR]

• Decaphenylcyclopentasilane-inserted perovskite solar cells were characterized. • Conversion efficiencies of DPPS-inserted cells were improved by annealing at 220 °C. • Surface coverage of the perovskite layer was improved by the DPPS insertion. • The DPPS layer suppressed the PbI 2 formation and improved the device stability. • After 4 weeks, the 190 °C-heated device provided the highest conversion efficiency. Perovskite solar cells, in which decaphenylcyclopentasilane (DPPS) layers were formed on the surface of the CH 3 NH 3 PbI 3 perovskite layer, were fabricated and characterized. The photovoltaic properties were improved by controlling the annealing temperature of the perovskite layer. For perovskite layers annealed at high temperatures of ~200 °C, the perovskite crystals were densely formed and the surface coverage of the perovskite layer was improved. The DPPS-laminated devices suppressed the formation of PbI 2 crystals and the stability was improved by the DPPS layer. [ABSTRACT FROM AUTHOR]

• Potassium compound-added perovskite solar cells were fabricated and characterized. • The conversion efficiencies were improved by addition of KCl. • The lattice constant of the perovskite increased by the KCl addition. • The addition of the K salts resulted in fine grained perovskite crystals. • The K occupied the MA/FA defects within the perovskite crystals. Perovskite solutions that were doped with potassium (K) salts (CH 3 NH 3) 0.8 (HC(NH 2) 2) 0.1 K 0.1 PbI 3 (MA 0.8 FA 0.1 K 0.1 PbI 3 (Cl)) were used to fabricate perovskite solar cells. The addition of the K salts resulted in fine grained perovskite crystals that were separated by very small gaps. These materials were used to fabricate solar cells that improved short circuit current densities, which resulted in an enhanced conversion efficiency, compared with standard materials. The K occupied the (CH 3 NH 3)/(HC(NH 2) defects within the perovskite crystals, which caused the lattice constant to increase. Additionally, the presence of K in the perovskite solutions promoted the growth of grains within the perovskite crystals. [ABSTRACT FROM AUTHOR]