Intrinsic thermal stability of inverted perovskite solar cells based on electrochemical deposited PEDOT

Thermal stability of perovskite materials is an issue impairing the long-term operation of inverted perovskite solar cells(PSCs). Herein, the thermal attenuation mechanism of the MAPb I3films that deposited on two different hole transport layers(HTL), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS) and poly(3,4-ethylenedioxythiophene)(PEDOT), is comprehensively studied by applying a heat treatment at 85℃. The thermal stress causes the mutual ions migration of I, Pb and Ag through the device, which leads to the thermal decomposition of perovskite to form Pb I2. Interestingly, we find that I ions tend to migrate more towards electron transport layer(ETL) during heating, which is different with the observation of I ions migration towards HTL when bias pressure is applied. Moreover, the use of electrochemical deposited PEDOT as HTL significantly decreases the defect density of MAPb I3films as compared to PEDOT:PSS supported one. The electrochemical deposition PEDOT has good carrier mobility and low acidity, which avoids the drawbacks of aqueous PEDOT:PSS. Accordingly, the inverted PSCs based on PEDOT show superior durability than that with PEDOT:PSS. Our results reveal detailed degradation routes of a new kind of inverted PSCs which can contribute to the understanding of the failure of thermal-aged inverted PSCs.

Double Layer Composite Electrode Strategy for Efficient Perovskite Solar Cells with Excellent Reverse-Bias Stability

Perovskite solar cells(PSCs)have become the represent-atives of next generation of photovoltaics;nevertheless,their stability is insufficient for large scale deployment,particularly the reverse bias stability.Here,we propose a transparent conducting oxide(TCO)and low-cost metal composite electrode to improve the stability of PSCs without sacrificing the efficiency.The TCO can block ion migrations and chemical reactions between the metal and perovskite,while the metal greatly enhances the conductivity of the composite electrode.As a result,composite electrode-PSCs achieved a power conversion efficiency(PCE)of 23.7%(certified 23.2%)and exhibited excellent stability,maintaining 95%of the initial PCE when applying a reverse bias of 4.0 V for 60 s and over 92%of the initial PCE after 1000 h continuous light soaking.This composite electrode strategy can be extended to different combinations of TCOs and metals.It opens a new avenue for improving the stability of PSCs.

Suppressed recombination for monolithic inorganic perovskite/silicon tandem solar cells with an approximate efficiency of 23%

Potentially temperature-resistant inorganic perovskite/silicon tandem solar cells(TSCs)are promising devices for boosting efficiency past the single-junction silicon limit.However,undesirable non-radiative recombination generally leads to a significant voltage deficit.Here,we introduce an effective strategy using nickel iodide,an inorganic halide salt,to passivate iodine vacancies and suppress non-radiative recombination.NiI_(2)-treated CsPbI_(3-x)Br_(x) inor-ganic perovskite solar cells with a 1.80 eV bandgap exhibited an efficiency of 19.53%and a voltage of 1.36 V,corresponding to a voltage deficit of 0.44 V.Importantly,the treated device demonstrated excellent operational stability,maintaining 95.7%of its initial efficiency after maximum power point tracking for 300 h under continuous illumination in a N_(2) atmosphere.By combining this inorganic perovskite top cell with a narrower bandgap silicon bottom cell,we for the first time achieved monolithic inorganic perovskite/silicon TSCs,which exhibited an effi-ciency of 22.95%with an open-circuit voltage of 2.04 V.This work provides a promising strategy for using inorganic passivation materials to achieve efficient and stable solar cells.

Perovskite Solar Cells Yielding Reproducible Photovoltage of 1.20 V

High photovoltages and power conversion efciencies of perovskite solar cells(PSCs)can be realized by controlling the undesired nonradiative charge carrier recombination.Here,we introduce a judicious amount of guanidinium iodide into mixed-cation and mixed-halide perovskite flms to suppress the parasitic charge carrier recombination,which enabled the fabrication of>20%efcient and operationally stable PSCs yielding reproducible photovoltageas high as 1.20 V.By introducing guanidinium iodide into the perovskite precursor solution,the bandgap of the resulting absorber material changed minimally;however,the nonradiative recombination diminished considerably as revealed by time-resolved photoluminescence and electroluminescence studies.Furthermore,using capacitance-frequency measurements,we were able to correlate the hysteresis features exhibited by the PSCs with interfacial charge accumulation.Tis study opens up a path to realize new record efciencies for PSCs based on guanidinium iodide doped perovskite flms.

Chemically tailored molecular surface modifiers for efficient and stable perovskite photovoltaics

Perovskite solar cells(PSCs)have attracted intense attention based on their high power conversion efficiency and low production cost.However,due to the polycrystalline nature and the intrinsic hydrophilicity of the metal halide perovskite moieties,the photovoltaic performance of PSCs is largely limited by defects within the polycrystalline perovskites and the sensitivity to moisture.In this perspective,we focus on the chemically tailored interface materials to passivate the defects and improve the moisture stability of PSCs.First,we provide a brief overview of various molecular interface modifiers.Thereafter we provide examples from our recent work on organic ammonium halide‐based passivation materials as representatives to illustrate the design strategies and the modification effects.In the end,we shed light on the future devel-opment of organic ammonium halides for applications in PSCs.

Regulated CO adsorption by the electrode with OH^(-) repulsive property for enhancing C–C coupling

Electrochemical CO_(2) reduction driven by renewable electricity is one of the promising strategies to store sus-tainable energy as fuels.However,the selectivity of value-added multi-carbon products remains poor for further application of this process.Here,we regulate CO adsorption by forming a Nafion layer on the copper(Cu)electrode that is repulsive to OH^(-),contributing to enhanced selectivity of CO_(2) reduction to C_(2) products with the suppression of C 1 products.The operando Raman spectroscopy indicates that the local OH^(-)would adsorb on part of active sites and decrease the adsorption of CO.Therefore,the electrode with repulsive to OH^(-)can adjust the concentration of OH^(-),leading to the increased adsorption of CO and enhanced C–C coupling.This work shows that electrode design could be an effective strategy for improving the selectivity of CO_(2) reduction to multi-carbon products.

Mechanistic Insight into Supramolecular Polymerization in Water Tunable by Molecular Geometry

Supramolecular self-assembly in water based on non-covalent bonding is attracting major attention due to the potential of hydrogels and aqueous polymers in biomedical applications.Although supramolecular polymerization in organic solvents is well established,the key design features,the assembly mechanisms in water and achieving control over the aggregate structures remain challenging.Here,we present the assembly and disassembly of geometrical isomers of a stiff-stilbene bis-urea amphiphile(SA)in pure water.A remarkable feature of this system is that the(E)-isomer forms supramolecular polymers in both pure water and organic solvents.Taking advantage of this unique property,the hydrophobic effect was studied by comparing the supramolecular assembly in both systems.The assembly process inwater follows an enthalpy-driven nucleation-elongation(cooperative)supramolecular polymerization mechanism with a standard Gibbs free energy(ΔG°=−53 kJ mol^(−1))double the value of the one found in toluene.We attributed this distinctive feature to the hydrophobic effect in water.Furthermore,we discovered an isomer-dependent assembly process,which can be used to control aggregation in aqueous media.Due to the substantial geometric difference between(E)-SA and(Z)-SA,we compared their assembly in water to study the influence of different driving forces involved in the process.The supramolecular polymerization of(E)-SA was cooperatively influenced by hydrogen bonding,π-stacking,and hydrophobic effects,whereas the assembly of(Z)-SAwasmainly driven by hydrophobic effects.As a result,the fiber length of(E)-SA in water is much longer than that of(Z)-SA,presenting opportunities for geometrical control of aggregation in aqueousmedia.