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.

Brominated PEAI as Multi-Functional Passivator for High-Efficiency Perovskite Solar Cell

The interfaces of perovskite solar cells(PSCs)are well known to be rich in deep-level carrier traps,which serve as non-radiative recombination centers and limit the open-circuit voltage(Voc)and power conversion efficiency(PCE)of PSCs.Defect chemistry and surface passivators have been researched extensively and mainly focused on the neutralization of uncoordinated lead or anion defects.Herein,a novel brominated passivator 2-bromophenethylammonium iodide(2-Br-PEAI)is introduced for a multi-functional passivation effect at the perovskite interface.The brominated species readily form 2D perovskite on top of the 3D perovskite and multi-interact with the 3D perovskite surface.Apart from the halide vacancy filling and anion bonding ability,the Br atoms on the benzene ring can interact with the FA cations via strong hydrogen bonding N-H…Br and interact with the[PbI_(6)]^(4−)inorganic framework.The interface defects in the PSCs are well passivated,minimizing non-radiative recombination and enhancing device performance.As a result,a champion PCE of 24.22%was achieved with high V_(oc)and fill factor.In addition,modified devices also showed enhanced operational stability(retention of>95%initial PCE after 400 h)and humidity resistance(>90%initial PCE maintained after 1500 h under~50%RH).

Defects engineering for high-performance perovskite solar cells

Metal halide perovskites have achieved great success in photovoltaic applications during the last few years.The solar to electrical power conversion efficiency(PCE)of perovskite solar cells has been rapidly improved from 3.9%to certified 22.7%due to the extensive efforts on film deposition methods,composition and device engineering.Further investigation on eliminating the defect states in perovskite absorbers is necessary to push forward the PCE of perovskite solar cells approaching the Shockley-Queisser limit.In this review,we summarize the defect properties in perovskite films and present methodologies to control the defects density,including the growth of large size crystals,photo-curing method,grain boundary and surface passivation,and modification of the substrates.We also discuss the defects-related stability and hysteresis issues and highlight the current challenges and opportunities in defects control of perovskite films.

Multifunctional succinate additive for flexible perovskite solar cells with more than 23%power-conversion efficiency

Flexible perovskite solar cells(FPSCs)have emerged as power sources in versatile applications owing to their high-efficiency characteristics,excellent flexibility,and relatively lowcost.Nevertheless,undesired strain in perovskite films greatly impacts the power-conversion efficiency(PCE)and stability of PSCs,particularly in FPSCs.Herein,a novel multifunctional organic salt,methylammonium succinate,which can alleviate strain and reinforce grain boundaries,was incorporated into the perovskite film,leading to relaxed microstrain and a lower defect concentration.As a result,a PCE of 25.4%for rigid PSCs and a record PCE of 23.6%(certified 22.5%)for FPSCs have been achieved.In addition,the corresponding FPSCs exhibited excellent bending durability,maintaining
85%of their initial efficiency after bending at a 6 mm radius for 10000 cycles.

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.