Superior Carrier Lifetimes Exceeding 6 µs in Polycrystalline Halide Perovskites

Abstract

such as charge-carrier lifetimes and diffusion lengths in perovskite films should be maximized, which are sensitive to the density of sub-bandgap trap states acting as nonradiative recombination centers. [12,13] Long carrier lifetimes and diffusion lengths imply a reduction in trap densities constituted by multidimensional defects that can be broadly observed at the grain boundaries and surfaces of polycrystalline perovskite films. Therefore, defect modulation to efficiently suppress the undesired nonradiative recombination pathways in perovskite films have resulted in dramatically enhanced carrier lifetimes and diffusion lengths, which can be translated into higher open-circuit voltage (V OC) of photovoltaic devices. [14-18] Recently, surface post-treatments, such as depositing a layer of ammonium salts onto the perovskites, are the most frequently employed strategies, passivating the defects in the topmost area of the perovskite films. [19-22] However, the additional depositing procedure is considered to bring much uncertainty to the original perovskite films. [23,24] Recently, Yoo et al. demonstrated that the commonly used solvents (e.g., isopropanol) for dissolving ammonium salts, due to their strong polarity, had negative effects on the underlying perovskite films. [25] Lead halide perovskite films have witnessed rapid progress in optoelectronic devices, whereas polycrystalline heterogeneities and serious native defects in films are still responsible for undesired recombination pathways, causing insufficient utilization of photon-generated charge carriers. Here, radiationenhanced polycrystalline perovskite films with ultralong carrier lifetimes exceeding 6 μs and single-crystal-like electron-hole diffusion lengths of more than 5 μm are achieved. Prolongation of charge-carrier activities is attributed to the electronic structure regulation and the defect elimination at crystal boundaries in the perovskite with the introduction of phenylmethylammonium iodide. The introduced electron-rich anchor molecules around the host crystals prefer to fill the halide/organic vacancies at the boundaries, rather than form low-dimensional phases or be inserted into the original lattice. The weakening of the electron-phonon coupling and the excitonic features of the photogenerated carriers in the optimized films, which together contribute to the enhancement of carrier separation and transportation, are further confirmed. Finally the resultant perovskite films in fully operating solar cells with champion efficiency of 23.32% are validated and a minimum voltage deficit of 0.39 V is realized. Polycrystalline halide perovskites are of enormous excitement to be applied in highly efficient solar cells, [1-3] light-emitting diodes, [4] lasers, [5,6] and high-sensitivity photodetectors [7,8] due to their low fabricating costs [9,10] and excellent optoelectronic properties. [11] In order for these optoelectronic devices to access their theoretical performance limits, key metrics

Surfactant Sodium Dodecyl Benzene Sulfonate Improves the Efficiency and Stability of Air‐Processed Perovskite Solar Cells with Negligible Hysteresis

“…[ 77,78 ] As shown in the band alignment diagram of Figure 7c, the optimized band alignment could improve the driving force of electron injection from the perovskite layer to the SnO 2 ETL, and enables a facilitated transportation of electrons. [ 79,80 ]…”

Dually‐Passivated Perovskite Solar Cells with Reduced Voltage Loss and Increased Super Oxide Resistance

“…Perovskite films fabricated via traditional solution process are prone to produce defects at the surfaces and GBs, which serve as non‐radiative recombination centers leading to an overall reduction of efficiencies and poor stability of the device [10] . The chemical passivation of those defects can be rationalized into two main strategies: i. mixing additive substances in the precursor solutions [11, 12] or antisolvents [13–16] to control perovskite growth and/or passivate defects in perovskite GBs; ii. surface modification via coating functional molecules on the preformed perovskite layer.…”

Buried Interfaces in Halide Perovskite Photovoltaics

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Halide perovskite photovoltaics have gained enormous attention because of their ever-increasing power conversion efficiencies (PCEs) over the past few years. [1][2][3][4][5][6] Further improvements in the performance of perovskite photovoltaics are hampered by a lack of in-depth understanding of the heterojunction interfaces and optimal interface designs, [7][8][9] specifically the buried interfaces within polycrystalline perovskite films. [10][11][12][13][14] Studies to date have focused on the top surfaces, [15][16][17] yet undesirable non-radiative losses that hinder the device power outputs are known to exist at the interfaces with bottom contact layers due to the accumulation of deep-level trap states.

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