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Second‐order distributed feedback (DFB) resonators are widely used for thin‐film lasers as they combine low lasing thresholds with ease of manufacturing. Here, the grating design parameters are varied to map the lasing characteristics of lead halide perovskite films deposited on a single substrate that contains hundreds of high‐quality silicon nitride surface gratings. The lowest lasing threshold (≈130 µJ cm−2) is identified through the aid of near‐field and far‐field imaging spectroscopy in a four‐dimensional design space composed of grating period, duty cycle, active layer thickness, and cavity length. Moreover, it is shown that antisymmetric modes support high‐quality lasing (Q up to ≈10800) in the second‐order DFBs. The multi‐dimensional experimental analysis is accompanied by a thorough theoretical study with a semi‐empirical model based on coupled wave equations, which is used to investigate the lasing characteristics beyond the manufacturing range. The results can be applied to a broad range of thin‐film DFB resonators, enabling the design of more complex laser stack configurations including light‐emitting devices for current‐injection lasing. [ABSTRACT FROM AUTHOR]

As the threshold for stimulated emission is significantly reduced at cryogenic temperatures, cooling of perovskite light emitting diodes (PeLEDs) is considered an essential strategy for reaching injection lasing in perovskite diodes. In this work, we demonstrate the intense electrical pulsing of a PeLED stack up to a few kA cm−2 at cryogenic conditions. A high external quantum efficiency (EQE) of 2.9% at 1 kA cm−2 and a radiance >1.95 × 105 W Sr−1 m−2 are achieved when exciting the device with 250 ns electrical pulses at 77 K, showing three times enhancement in comparison with room temperature operation. Furthermore, we provide a comprehensive understanding on how the ion distribution can affect the PeLED characteristics and show that ion motions can be manipulated at cryogenic conditions. This opens new routes for novel material and device designs for further improving PeLED performance. [ABSTRACT FROM AUTHOR]

Although perovskite light emitting diodes (PeLEDs) have shown fast advances in external quantum efficiency (EQE), their operational stability is still low compared to other LED devices. Here, stable PeLEDs are demonstrated with high radiance primarily by using 6,6′‐phenyl‐C61‐butyric acid methyl ester (PCBM) and magnesium‐doped Zinc oxide (ZnMgO) injection layers to reduce the driving voltage. Through different characterizations, it is revealed that the use of PCBM/ZnMgO electron injection layer can effectively mitigate Joule heating, block the migration of Al electrode towards perovskite layer as well as avoid the breakdown of main perovskite crystal structure under prolonged operation. Combining the PCBM/ZnMgO electron injection layer with a formamidinium‐based perovskite light emitter, the optimal device shows an EQE of 11.4% at 330 mA cm−2 and a radiance of 399 W Sr−1 m−2 at 3.1 V. The device remains above 50% of the maximum performance after operating for 525 and 118 h at constant current densities of 50 and 100 mA cm−2, respectively. Thus, this work presents a substantial improvement in the stability of PeLEDs and the methods to consolidate this progress even further. [ABSTRACT FROM AUTHOR]

The reproducibility of results is one of the cornerstones of scientific research. However, in emerging technologies, the reported results often tend to be sensitive to the chosen measurement protocol. This can stem from measurement artifacts or from unknown complex underlying phenomena. Metal halide perovskites have emerged as an exciting material system for optoelectronic devices. The anomalous hysteresis in the current density–voltage (J–V) characteristics of perovskite solar cells has triggered wide discussions on how to report their power conversion efficiency to achieve consistency between different research groups. However, less attention is so far given to the anomalous effects that can affect the reporting of the characteristics of perovskite light emitting diodes (PeLEDs). Here, it is shown that even for PeLEDs with little J–V hysteresis, the transient response and hysteresis of electroluminescence (EL), likely caused by ion migration, heat accumulation, and device degradation under electrical excitation, can lead to significantly different device characteristics depending on the measurement procedures for the same device. Therefore, a method based on pulsed excitation that allows for better reproducibility and interpretation of the measured device characteristics is proposed. Furthermore, suggestions are also provided on reporting PeLED characteristics, as input for further discussions in the scientific community. [ABSTRACT FROM AUTHOR]

Thin‐film photovoltaic technology, based on hybrid metal halide perovskites, has achieved 25.2% and 16.1% certified power conversion efficiencies for solar cell and solar module devices, respectively. Still, the gap between power conversion efficiency of small area solar cells and large area solar modules is greater than for any other photovoltaic technology. Analysis of loss mechanisms in n‐i‐p solution processed devices defined layer inhomogeneity loss and inactive area loss as the two most prominent loss mechanisms in upscaling. In this study, we focus on minimizing inactive area loss. We analyze the point contact interconnections design and demonstrate it on perovskite thin‐film solar modules to achieve a geometrical fill factor of up to 99%. Numerical and analytical simulations are utilized to optimize interconnections and solar module design and balance inactive area loss, series resistance loss, and contact resistance loss. [ABSTRACT FROM AUTHOR]

Perovskite‐based multijunction solar cells can potentially overcome the power conversion efficiency (PCE) limits of established solar cell technologies. The technology combines high‐efficiency perovskite top solar cells with crystalline silicon (c‐Si) and copper indium gallium diselenide (CIGS) single‐junction solar cells enabling a more efficient harnessing of solar energy. In this work, we present high‐efficiency and scalable perovskite‐CIGS and perovskite‐Si multijunction solar modules in a four‐terminal configuration. We design the multijunction solar modules for minimal optical losses through careful optical engineering. In addition to optimized light coupling, the solar modules are fabricated in a scalable device design. Starting from lab‐scale cells of 0.13 cm2, we scale up the multijunction devices by two orders of magnitude to 16 cm2 and investigate the various losses affecting the PCE of large‐area multijunction solar modules, thus providing valuable insights into scalability of the technology. The champion perovskite‐CIGS and perovskite‐Si multijunction solar modules exhibit higher PCE than the stand‐alone devices on sizes up 16 cm2, paving the way for high‐effiency perovskite‐based multijunction photovoltaics. This work brings to forth relevant upscaling aspects of perovskite‐based multijunction solar cell technology, which is a key milestone in the road to commercial feasibility of the perovskite‐based multijunction solar cell technology. [ABSTRACT FROM AUTHOR]

Abstract: Stability is one of the key challenges for industrial scale commercialization of perovskite solar cells. In this work, a degradation mechanism that depends on materials and bias conditions of the device during light‐soaking is proposed. The observed degradation is linked to the additive 4‐tert‐butyl pyridine (tBP), crucial to the hole transport layer of most perovskite solar cells, and gold. This conclusion is reached through the statistical analysis of multiple compositional profiles of light‐soaked and nonlight‐soaked devices and by selective replacement of material layers of the device. Moreover, the rate of the light‐induced degradation is enhanced by operation at forward bias, which is required for power generation. Thus, this work stresses the need for the development of transport layers that do not require tBP, and to replace gold to produce high‐performing devices that are also stable under operating conditions. [ABSTRACT FROM AUTHOR]

Abstract: Photovoltaic cells and modules are exposed to partially rapid changing environmental parameters that influence the device temperature. The evolution of the device temperature of a perovskite module of 225 cm2 area is presented during a period of 25 days under central European conditions. The temperature of the glass–glass packaged perovskite solar module is directly measured at the back contact by a thermocouple. The device is exposed to ambient temperatures from 3 to 34 °C up to solar irradiation levels exceeding 1300 W m−2. The highest recorded module temperature is 61 °C under constant high irradiation levels. Under strong fluctuations of the global solar irradiance, temperature gradients of more than 3 K min−1 with total changes of more than 20 K are measured. Based on the experimental data, a dynamic iterative model is developed for the module temperature evolution in dependence on ambient temperature and solar irradiation. Furthermore, specific thermal device properties that enable an extrapolation of the module response beyond the measured parameter space can be determined. With this set of parameters, it can be predicted that the temperature of the perovskite layer in thin‐film photovoltaic devices is exceeding 70 °C under realistic outdoor conditions. Additionally, perovskite module temperatures can be calculated in final applications. [ABSTRACT FROM AUTHOR]

Multijunction solar cells employing perovskite and crystalline-silicon (c-Si) light absorbers bear the exciting potential to surpass the efficiency limit of market-leading single-junction c-Si solar cells. However, scaling up this technology and maintaining high efficiency over large areas are challenging as evidenced by the small-area perovskite/c-Si multijunction solar cells reported so far. In this work, a scalable four-terminal multijunction solar module design employing a 4 cm2 semitransparent methylammonium lead triiodide perovskite solar module stacked on top of an interdigitated back contact c-Si solar cell of identical area is demonstrated. With a combination of optimized transparent electrodes and efficient module design, the perovskite/c-Si multijunction solar modules exhibit power conversion efficiencies of 22.6% on 0.13 cm2 and 20.2% on 4 cm2 aperture area. Furthermore, a detailed optoelectronic loss analysis along with strategies to enhance the performance is discussed. [ABSTRACT FROM AUTHOR]

The fabrication of high-quality cesium (Cs)/formamidinium (FA) double-cation perovskite films through a two-step interdiffusion method is reported. Cs xFA1- xPbI3-y(1- x)Bry(1- on the properties of the resulting perovskite films and on the performance of the corresponding perovskite solar cells are systematically studied. Small area perovskite solar cells with a power conversion efficiency (PCE) of 19.3% and a perovskite module (4 cmx)) with an aperture PCE of 16.4%, using the Cs/FA double cation perovskite made with 10 mol% CsI and 15 mol% FABr (Cs+ and Br− on the properties of the resulting perovskite films and on the performance of the corresponding perovskite solar cells are systematically studied. Small area perovskite solar cells with a power conversion efficiency (PCE) of 19.3% and a perovskite module (4 cm2) with an aperture PCE of 16.4%, using the Cs/FA double cation perovskite made with 10 mol% CsI and 15 mol% FABr (Cs0.1) are achieved. The Cs/FA double cation perovskites show negligible degradation after annealing at 85 °C for 336 h, outperforming the perovskite materials containing methylammonium (MA). [ABSTRACT FROM AUTHOR]0.9PbI2.865Br0.135) are achieved. The Cs/FA double cation perovskites show negligible degradation after annealing at 85 °C for 336 h, outperforming the perovskite materials containing methylammonium (MA). [ABSTRACT FROM AUTHOR]

Cost-effective production of perovskite solar cells on an industrial scale requires the utilization of exclusively inexpensive materials. However, to date, highly efficient and stable perovskite solar cells rely on expensive gold electrodes since other metal electrodes are known to cause degradation of the devices. Finding a low-cost electrode that can replace gold and ensure both efficiency and long-term stability is essential for the success of the perovskite-based solar cell technology. In this work, we systematically compare three types of electrode materials: multi-walled carbon nanotubes (MWCNTs), alternative metals (silver, aluminum, and copper), and transparent oxides [indium tin oxide (ITO)] in terms of efficiency, stability, and cost. We show that multi-walled carbon nanotubes are the only electrode that is both more cost-effective and stable than gold. Devices with multi-walled carbon nanotube electrodes present remarkable shelf-life stability, with no decrease in the efficiency even after 180 h of storage in 77% relative humidity (RH). Furthermore, we demonstrate the potential of devices with multi-walled carbon nanotube electrodes to achieve high efficiencies. These developments are an important step forward to mass produce perovskite photovoltaics in a commercially viable way. [ABSTRACT FROM AUTHOR]

Replacing toxic solvents with nonhazardous solvents is one of the key challenges for industrial scale commercialization of thin film perovskite photovoltaics. Here, nonhazardous solvent/alcohol/acid systems are presented for the single-step deposition of pinhole-free perovskite layers with combined lead halide precursors of Pb(CH3CO2)2·3H2O, PbCl2, and CH3NH3I. Comparable performance to standard hazardous inks is achieved: devices with 15.1% power conversion efficiency are demonstrated and maintain 13.5% tracked for 5 min at maximum power point. Blade coated 4 cm2 solar modules fabricated with highest performing device ink attain 11.9% in power conversion efficiency. [ABSTRACT FROM AUTHOR]

Perovskite light emitting diodes (PeLEDs) have reached external quantum efficiencies (EQEs) over 21%. Their EQE, however, drops at increasing current densities (J) and their lifetime is still limited to just a few hours. The mechanisms leading to EQE roll‐off and device instability require thorough investigation. Here, improvement in EQE, EQE roll‐off, and lifetime of PeLEDs is demonstrated by tuning the balance of electron/hole transport into a mixed 2D/3D perovskite emissive layer. The mixed 2D/3D perovskite layer induces exciton confinement and beneficially influences the electron/hole distribution inside the perovskite layer. By tuning the electron injection to match the hole injection in such active layer, a nearly flat EQE for J = 0.1–200 mA cm−2, a reduced EQE roll‐off until J = 250 mA cm−2, and a half‐lifetime of ≈47 h at J = 10 mA cm−2 is reached. A model is also proposed to explain these improvements that account for the spatial electron/hole distributions. [ABSTRACT FROM AUTHOR]

Determining the accurate power output of perovskite‐based thin film solar cells is dependent on measuring conditions and parameters. In article no. 1800287, Lucija Rakocevic and co‐workers show how the choice of measuring parameters can alter the measured performance in maximum power point tracking. A measuring procedure for comparison of different perovskite‐based nip architectures is proposed. [ABSTRACT FROM AUTHOR]

In article number 1600386, Jeffrey G. Tait and co ‐ workers develop non ‐ hazardous ink systems, based on solvENt ‐ alcohol ‐ acid, for coating perovskite photovoltaic films in a single step. Coating was further developed from spin to blade, while the high yield process produced efficiENt 4 cm2 modules. [ABSTRACT FROM AUTHOR]

An accurate electrical device characterization of hybrid organic-inorganic halide perovskite solar cells (PSCs) is an important prerequisite for further improvement and industrial transfer of this promising photovoltaic technology. In this work, we study the nonlinearity of current versus irradiance as well as the temperature dependence of PSCs in a spectrally resolved manner by highly accurate differential external quantum efficiency (EQE) measurements. We investigate three different types of PSCs fabricated by different research groups. The nonlinearity of all samples is found to be spectrally invariant, which significantly simplifies spectral mismatch corrections. We demonstrate that misinterpretation of EQE measurements can result in a more than 10% relative error in efficiency measurements, if solar simulators are adjusted to photocurrents determined from differential EQEs. For obtaining an accurate integrated photocurrent from EQEs, we introduce a new, convenient approach that accounts for cell nonlinearities but avoids the time-consuming full analysis of spectrally resolved nonlinearity. Moreover, for the samples investigated here, it is shown that the differential EQE measured at 0.35 suns bias irradiance represents a reasonably good estimate of the actual EQE at 1 sun. Furthermore, we determine spectrally resolved temperature coefficients (TCs) and show how the band gap blue shift varies with perovskite absorber and temperature. [ABSTRACT FROM AUTHOR]

Scalable sheet-to-sheet slot die coating processes have been demonstrated for perovskite solar cells and modules. The processes have been developed on 6 in. × 6 in. glass/ITO substrates for two functional layers: the perovskite photo-active layer and the Spiro-OMeTAD hole transport layer. Perovskite solar cells produced using these slot die coating processes demonstrate device performances identical to the spin coated devices. All manufactured devices illustrate a high level of reproducibility. The developed slot die coating processes were also used for the manufacturing of perovskite PV modules. Large area modules of 12.5 × 13.5 cm 2 were realized by slot die coating on 6 in. × 6 in. substrates in combination with newly developed laser ablation processes for conventional P1-P2-P3 monolithic cell interconnections. The modules demonstrate power conversion efficiencies above 10%, with a power output of 1.7 W. This achievement is an important milestone in the development of up-scalable manufacturing technologies for perovskite PV modules. [ABSTRACT FROM AUTHOR]