This review summarizes the recent achievements in flexible OLEDs involving transparent conductive electrodes, device fabrication, light extraction technologies, as well as encapsulation methods.
Organometal halide perovskites exhibit a bright future for applications in solar cells, as efficiency has achieved over 22%. The long‐term stability remains a major obstacle for commercialization. Here, it is found that three cationic compositional engineered perovskites, MAPb(I0.83Br0.17)3, FA0.83MA0.17Pb(I0.83Br0.17)3, and Cs0.1(FA0.83MA0.17)0.9Pb(I0.83Br0.17)3, undergo severe degradation under white‐light illumination in ultrahigh vacuum (UHV) environment, but the rate of degradation is significantly lower for the mixed cation perovskites. This is attributed to the defect‐induced trap states that trigger the strong coupling between the photoexcited carriers and the crystal lattice. The observed behavior supports the view of the mixed cations suppressing the photoinduced degradation. It is further demonstrated that UHV environment remarkably accelerates the degradation of the perovskite films under illumination, which delivers a very important message that the current hybrid perovskite materials and their optoelectronic devices are not suitable for application in outer space. Moreover, the applied UHV environment can be an accelerated test method to estimate the photostability of the perovskites.
Organometal mixed-halide perovskite materials hold great promise for next-generation solar cells, light-emitting diodes, lasers, and photodetectors. Except for the rapid progress in the efficiency of perovskite-based devices, the stability issue over prolonged light illumination has severely hindered their practical application. The deterioration mechanism of organometal halide perovskite materials under light illumination has seldom been conducted to date, which is indispensable to the understanding and optimization of photon-harvesting process inside perovskite-based optoelectronic devices. Here, explicit degradation pathways and comprehensive microscopic understandings of white-light-induced degradation have been put forward for two organometal mixed-halide perovskite materials (e.g., MAPbICl and MAPbBrCl) under high vacuum conditions. In situ compositional analysis and real-time film characterizations reveal that the decomposition of both mixed-halide perovskites starts at the grain boundaries, leading to the formation of hydrocarbons and ammonia gas with the residuals of PbI(Cl), Pb, or PbClBr in the films. The degradation has been correlated to the localized trap states that induce strong coupling between photoexcited carriers and the crystal lattice.
perovskite materials. [1][2][3][4][5][6][7] Since 2009, rapid progress has been made on the performance of methylammonium lead halide perovskite (CH 3 NH 3 PbX 3 , X = Cl, Br, I)based PeSCs with a substantial increase in power conversion efficiency (PCE) from 3.8% to a stunning value of more than 22%. [8][9][10] Typically, a PeSC is composed of a perovskite absorber layer sandwiched between the hole and the electron transport layers (HTLs and ETLs, respectively). [11] Upon the absorption of incident light, carriers will generate in the perovskite absorber and transport to HTL or ETL, and finally are collected by the corresponding electrodes. To achieve highly efficient and low-cost PeSCs, great efforts have been devoted to optimizing the perovskite material design, device structures and relevant processing techniques. [1][2][3][4][5][6][7][8][9][12][13][14][15] Apart from the major emphasis on perovskite film processing and interface modification for efficient charge collection, it is still of great challenges to achieve maximum light trapping within the devices and then make the majority of incident light for photoelectric conversion. For instance, the photocurrent density of the reported PeSCs were still lower than the theoretical one of ≈26 mA cm −2 , [16] indicating that quite a large fraction of incident light still remains unused for photocurrent generation. The increased physical thickness of the perovskite absorber allows for better light absorption, which however certainly reduces the charge collection efficiency due to the increased recombination current. To alleviate this contradiction, light-trapping schemes are imperative for effectively enhancing light harvesting efficiencies in PeSCs by increasing the internal scattering and absorption of incident light with lower recombination currents.To date, numerous light manipulation strategies using periodic or random structures have been proposed such as plasmonic structures, [17] microlens array, [18] metal nanoparticles, [19] aperiodic arrays, [20][21][22] microresonators, [23] and optical cavities. [24,25] By introducing these schemes to the appropriate interfaces in thin-film solar cells, light absorption can be effectively enhanced by guiding and retaining the incident light through the enhancement of optical path length or the spatial redistribution of light intensity due to surface plasmon resonances (SPRs). Nevertheless, most of these schemes are limited for the practical adoption in large-area solar cell fabrication Light management holds great promise of realizing high-performance perovskite solar cells by improving the sunlight absorption with lower recombination current and thus higher power conversion efficiency (PCE). Here, a convenient and scalable light trapping scheme is demonstrated by incorporating bioinspired moth-eye nanostructures into the metal back electrode via soft imprinting technique to enhance the light harvesting in organic-inorganic lead halide perovskite solar cells. Comparedto the flat reference cell with a methylammonium le...
Rapid progress in the power conversion efficiency (PCE) of polymer solar cells (PSEs) is beneficial from the factors that match the irradiated solar spectrum, maximize incident light absorption, and reduce photogenerated charge recombination. To optimize the device efficiency, a nanopatterned ZnO:Al O composite film is presented as an efficient light- and charge-manipulation layer (LCML). The Al O shells on the ZnO nanoparticles offer the passivation effect that allows optimal electron collection by suppressing charge-recombination loss. Both the increased refractive index and the patterned deterministic aperiodic nanostructure in the ZnO:Al O LCML cause broadband light harvesting. Highly efficient single-junction PSCs for different binary blends are obtained with a peak external quantum efficiency of up to 90%, showing certified PCEs of 9.69% and 13.03% for a fullerene blend of PTB7:PC BM and a nonfullerene blend, FTAZ:IDIC, respectively. Because of the substantial increase in efficiency, this method unlocks the full potential of the ZnO:Al O LCML toward future photovoltaic applications.
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