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Abstract Organic-inorganic hybrid perovskite with single or multiple ions is extensively investigated as light-harvesting material in fabricating high-efficiency photovoltaic cells. There is much less effort into the understanding of the structure and electronic properties than into device optimization. The highest efficiency usually appears some time (a couple of days) after the device fabrication, but the underlying mechanism is rarely in the limelight. Here we study device performance under different storage environments. We utilize X-ray diffraction, time-resolved photoluminescence, transient absorption spectrometer, and single-carrier diode measurement to understand the structure and electronic properties of perovskite films for the time scale of weeks. We observe enhanced crystallinity and crystallite size, referred to age-induced recrystallization. Based on the structural changes, the charge trap and recombination are suppressed, while charge transport and collection are enhanced, ultimately improving device efficiency. Graphical abstract Image 1 Highlights • Efficiency improvement in perovskite solar cells under different storage environments. • Planar-structure device efficiency 20% with V oc of 1.19 V. • The crystallinity and crystallite size is enhanced in the age-induced recrystallization. • The charge trap and recombination is suppressed, and charge transport is enhanced. [ABSTRACT FROM AUTHOR]

In recent years, some minor elements are added into silver paste in order to improve the Ag/Si contact properties for crystalline silicon solar cells. Nevertheless, along with the addition of minor elements, the early discoloration of silver electrode appears on solar cells. In this work, the deteriorated silver alloy electrode on crystalline silicon solar cells was analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results prove that there exists a small amount of bismuth sulfide on the surface of the deteriorated electrode compared with normal electrode. An important finding is that the photocatalytic reaction of bismuth sulfide can accelerate the early discoloration of the silver alloy electrode. Then, the effect of silver alloy electrode deterioration on the peel force of ribbon for solar cells was investigated. The results indicate that the peel strength between ribbons and solar cells is decreased sharply due to the poor solderability of the deteriorated electrode. Additionally, it is found that the deteriorated silver alloy electrode can be recovered at 450 °C annealing for 60 s in a sintering furnace. After recovery experiments, the average peel force of ribbons attached to recovered busbars is up to 85% of normal busbars. The peel force of ribbon is significantly improved. The results obtained in this paper indicate that more attention should be given to the negative effect of minor elements on the electrode, when minor elements are added into silver paste to improve its performance. • Photocatalytic reaction results in the early deterioration of Ag alloy electrode. • The photocatalytic reaction is caused by the additive composition in silver paste. • It is confirmed that the deteriorated Ag alloy electrode can be recovered. [ABSTRACT FROM AUTHOR]

We adsorbed fluorinated-alkyl (F m SAM) and hydrogenated-alkyl (H m SAM) phosphonic acids with different molecular lengths on anodes of bulk-heterojunction polymer solar cells. We found the fill factors and series resistances of devices having F m SAMs to more steeply depend on molecular length than those having H m SAMs. We attribute this phenomenon to the smaller tunneling decay factor of H m SAM compared to F m SAM, which is consistent with DFT calculations that reveal differences in the extents of electron density localization of the highest occupied molecular orbitals of these species. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigate the power degradation for crystalline silicon solar cells. [•] The binding force between silver paste and silicon should not be less than 2.0 N. [•] The hollowed-out silver busbar weaks the binding force. [ABSTRACT FROM AUTHOR]

Due to the non-homogeneous defect structure of the multicrystalline silicon material, the distribution of the electrical parameters in monolithic multicrystalline silicon solar cell depends on the quality of the material. In this paper, the distribution of the electrical parameters in monolithic multicrystalline silicon solar cell is investigated. The experimental evidence suggests that gettering and silicon nitride passivation can enhance the uniformity of the electrical parameters in monolithic multicrystalline silicon solar cell, even if impurity gettering is not effective when the dislocation density is above a threshold value of about 106 cm−2. Response to gettering of different regions of a multicrystalline silicon wafer is different. The experiments give us some hints that when we dice a large area multicrystalline silicon solar cell made by the mid and low quality multicrystalline silicon into small pieces needed by application, we should add some special process such as phosphorus gettering. [Copyright &y& Elsevier]

Minority carrier trapping centers frequently exist in solar grade multicrystalline silicon, such trapping centers cause a drastic increase in photoconductance at carrier injection levels equal to and below the trap density, this phenomenon leads to higher open circuit voltage for multicrystalline silicon solar cells at illumination levels below about 0.2 suns compared to high performance crystalline silicon solar cells. In this paper, the open circuit voltage of multicrystalline silicon solar cells are investigated at low illumination levels, the experiments prove that some multicrystalline silicon solar cells which have higher trap density have higher open circuit voltage at weak illumination levels, and have lower efficiency, so a new method is presented to analyze quality of multicrystalline silicon by measuring open circuit voltage at weak illumination levels in-line, this makes cells manufacturers gain insight into the quality of multicrystalline silicon wafer from different multicrystalline silicon manufacturers easily with the same cell process before screenprinting and firing. [Copyright &y& Elsevier]

• There exist electrochemical reactions in solar module exposed to system voltage. • A novel model was developed to quantify ions migration in silicon solar module. • The TEM reveals that there exist Na+ ions in solar cells. In this paper, the electrochemical reactions and ions migration of crystalline silicon solar module were investigated. Based on the different polarity system voltage, the equations of electrochemical reactions in crystalline silicon solar module were given out for the first time. A novel model was developed to quantify ions migration in crystalline silicon solar module. The outcome of calculation indicates that the migration time is mainly associated with the applied electric field and ambient temperature without regard to humidity. And the migration time across n+-p junction is far larger than that across SiN x :H layer, which suggests the migration of Na+ ions in perfect silicon is harder than that in SiN x :H layer, unless there exists stacking faults in n+-p junction. Finally, the transmission electron microscopy (TEM) was performed and that proves there exists a sparse distribution of Na+ ions in solar cells. The obtained results in this paper are beneficial to understand the electrochemical aging of module in the field. [ABSTRACT FROM AUTHOR]

Abstract: This article focuses on the electronic structure of the poly(3-hexylthiophene):phenyl-[6,6]-C61 butyric acid methyl ester (P3HT:PCBM) blend, widely used in bulk heterojunction (BHJ) solar cells. Given the fact that the surface of the blend film is a nearly pure P3HT wetting layer, we use a lift-off method to access the originally buried surface, which is rich in both P3HT and PCBM and thus representative of the BHJ. The combination of direct and inverse photoemission spectroscopy on this surface leads to a determination of the energy gap between the lowest unoccupied molecular orbital (LUMO) of the acceptor and the highest occupied molecular orbital (HOMO) of the donor. The gap is ∼1.4eV, which implies a 0.5–0.6eV interface dipole barrier between the two materials. The energy gap is found to be stable versus in situ annealing up to 100°C. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) metal halide perovskites (MHPs) incorporated with two-dimensional (2D) MHPs have been demonstrated to be a facile way to approach the high performance of perovskite photovoltaics (PPVs). In this study, we report high-performance PPVs, in terms of efficiency, detectivity, stability, and photocurrent hysteresis, based on the 3D mixed with 2D MHPs composites (termed as the 2D:3D mixed MHPs composites), where 4-fluoro-phenethylammonium, which possesses larger dipole moment compared to phenethylammonium, is used to create 2D MHPs. Systematically studies indicate that the 2D:3D mixed MHPs composites possess larger crystals, higher crystallinity, and enhanced charge transport compared to 3D MHPs thin film. As a result, the PPVs based on the 2D:3D mixed MHPs composites exhibit over 21.16 ± 0.53% power conversion efficiency with suppressed photocurrent hysteresis, over 1016 cm Hz1/2W−1 detectivity, and dramatically boosted stability. Our results indicate that we provide a facile way to approach high-performance PPVs. [Display omitted] • Three- and two-dimensional mixed (3D:2D) metal halide perovskite composites are prepared for approaching high-performance perovskite photovoltaics. • Perovskite solar cells based on the 3D:2D mixed halide perovskites composite thin film exhibit a power conversion efficiency of over 21.16 ± 0.53% and dramatically boosted stability. • Perovskite photodetectors based on the 2D:3D mixed perovskite composite thin film exhibit over 1016 cm Hz1/2W−1 detectivity and a linear dynamic range of 110 dB. [ABSTRACT FROM AUTHOR]

Metal halide perovskites are considered the most promising candidates for solar cells of the decade due to their exceptional optical and electronic properties. The power conversion efficiency of metal halide perovskites, when incorporated as the active layer of solar cells, has become comparable to that observed for conventional silicon solar cells. However, the stability, scaleup, green solvent usage, and fabrication in ambient conditions of metal halide perovskites need to be solved for commercial applications. Here, we report the fabrication of blade-coated methylammonium lead iodide (MAPbI 3) perovskite thin films using methylamine and acetonitrile as "green" solvents under ambient conditions. Our perovskite films are initially prepared from low purity PbI 2 (99%) and are blade-coated in dry air at relative humidity (RH) levels above 30%. A significant advantage of fabricating our perovskite thin films via blade-coating protocols is that there is a minimal amount of precursors (5 μL) used compared to spin-coating methods (50μL–60μL) for a 4 cm2 substrate. With the addition of a small amount of an organic halide salt, namely, phenethylammonium chloride, the film crystallinity is improved and non-radiative recombination is suppressed, resulting in power conversion efficiencies over 20%. In addition, the device maintains more than 95% of its initial efficiency after 500 h under continuous light illumination of 1-sun at open circuit conditions, 50 °C and 60% RH. The above method leads a path towards the commercial fabrication of perovskite solar cells. [Display omitted] • Low purity lead iodide is used to grow high quality perovskite films from blade coating method. • Volatile green solvents are used to prepare precursor to make dense, uniform, compact, and dark perovskite films. • Stable devices with efficiency over 20% are fabricated in ambient environment by adding phenethylammonium chloride. [ABSTRACT FROM AUTHOR]

Decreasing the thickness of perovskite absorption layer is significant for obtaining semi-transparent, tandem and flexible photovoltaic devices with high performance. However, the light harvesting would be influenced due to the limited absorption. Introducing plasmonic metal nanoparticles into perovskite solar cells (PSCs) is regarded as a promising approach on the development of ultra-thin PSCs. In this work, gold nanostars (Au NSs) with strong local electromagnetic field and SnO 2 surface modification layer were successfully incorporated into ultra-thin PSCs. This design increased light harvesting and carrier transporting. Furthermore, we systematically investigated the plasmon effect of Au NSs on the power conversion efficiency (PCE) of the PSCs with different thicknesses of the perovskite layer and observed that the deceased thickness of perovskite layer led to more intense PCE improvement as the same Au NSs were introduced. The ultra-thin PSCs with 250-nm perovskite layer show a PCE improvement from 15.34 to 18.50% after Au NSs/SnO 2 modification, accounting for a maximum enhancement factor of 20.60%. Simultaneously, the modified PSCs with 400-nm perovskite layer exhibit a best reported PCE of 20.06% for the plasmonic PSCs, with an enhanced factor of 13.70% and enhanced light stability. More importantly, flexible, large area and semi-transparent PSCs were also achieved. The flexible devices show more than 90% of their initial PCE values after 100 bending cycles. Our result promises a facile way for developing efficient, flexible and semi-transparent PSCs with ultra-thin absorption layer. Image 1 • The structure with FTO/c-TiO 2 /m-TiO 2 /Au NSs/SnO 2 /CsFAMA/Spiro-OMeTAD/Au is firstly fabricated. • Au NSs and SnO 2 modification layer increase light harvesting and carrier transporting. • The ultra-thin PSCs show a PCE of 18.50%, accounting for a maximum enhancement factor of 20.6%. • Modified PSCs exhibit a best reported PCE of 20.06% for the plasmonic PSCs. • Flexible, large area and transparent PSCs were achieved. [ABSTRACT FROM AUTHOR]

To make the jump from laboratories to commercial production for perovskite solar cells, it is necessary to develop devices in an ambient environment using materials and methods that can be scalable. Here, blade coating followed by vacuum quenching is used to manufacture the FACs-based perovskite solar cells with the additive of MACl under an ambient environment (30%–57% RH), where FA is formamidinium and MA is methylammonium. The vacuum allows quick removal of solvent to initiate the nucleation process and create the intermediate phase. To control the nucleation and crystallization, the additive MACl is utilized to manipulate the intermediate phase. Besides perovskites, another key component is the hole transport material. Although nickel oxide exhibits good photostability and can be scalable for the inverted device architecture, the main drawback is low cell efficiency. This work solves it by tuning the cation ratio of Pb2+ to A+ and light soaking, achieving a champion efficiency of 19.5%. The encapsulated solar cells exhibit long-term photostability, maintaining 96% of their original efficiency and 91.5% of their maximum efficiency over 648 h under one sun at 45°C and 50%–60% relative humidity. This work demonstrates an economical and highly scalable process, promising for commercial-scale manufacturing. Highly scalable FACs-based perovskite solar cells with additive of MACl are developed. Perovskite film is blade coated in air, assisted by vacuum quenching. The substrate also needs to be scalable with a low price, so hot spray prepared NiOx is the choice. We overcome its drawback of low open-circuit voltage by tuning the Pb-A ratio and light soaking, achieving efficiency close to 20%. [Display omitted] • Blade coating and vacuum-assisted method for making perovskite solar cells in air. • MACl is used to manipulate the intermediate phase during vacuum-assisted method. • Open-circuit voltage is improved by tuning organic cation/Pb ratio on NiOx. • Carrier lifetime at NiOx/perovskite interface becomes longer after light soaking. [ABSTRACT FROM AUTHOR]

The viability of commercial Ga-doped silicon PERC solar cell is decided by its efficiency, cost and reliability. In this article, the viability of Ga-doped Cz-Si PERC solar cells has been investigated systematically from an industrial perspective. Firstly, the relationship of wafer resistivity, contact fraction and variation of series resistance for PERC solar cell has been established for increasing the usage rate of Ga-doped crystal. Then, based on the relationship, an average efficiency of 22.21% for the PERC cells with five busbars fabricated from the whole Ga-doped CZ crystal has been achieved. The statistical results of electrical parameters show that the PERC cells fabricated on Ga-doped Cz-Si wafers with a wide resistivity variation (0.5–2.0 Ω⋅cm) are highly comparable with that of PERC cells made from B-doped Cz-Si wafers with typical resistivity (0.5–1.0 Ω⋅cm). The obtained results demonstrated that the full range of resistivity values produced from a Ga-doped Cz crystal can be used to fabricate quality, cost-effective PERC solar cells. Meanwhile, a comparative study of initial degradation for optimized Ga-doped PERC solar cells and stabilized B-doped PERC solar cells was carried out in accumulative irradiation of 20 kWh/m2 at 50 °C and 80 °C. The results indicate that Ga-doped PERC cells are more stable than stabilized B-doped PERC cells even though at high temperature. The results obtained in this paper demonstrate the viability of Ga- instead of B-doped Cz-Si wafer as substrate to fabricate cost-effective PERC solar cells. • The viability of Ga-doped Cz-Si PERC solar cells has been investigated systematically from an industrial perspective for the first time. • It has been demonstrated that the full range of resistivity values produced from a Ga-doped Cz crystal can be used to fabricate a quality, cost-effective PERC solar cell. • The relationship of wafer resistivity, contact fraction and variation of series resistance for PERC solar cell has been established, and it has been demonstrated experimentally. • The results of degradation show that Ga-doped PERC cells are more stable than stabilized B-doped PERC cells. [ABSTRACT FROM AUTHOR]