Search

Following the rapid increase of organic metal halide perovskites toward commercial application in thin-film solar cells, inorganic alternatives attracted great interest with their potential of longer device lifetime due to the stability improvement under increased temperatures and moisture ingress. Among them, cesium lead iodide (CsPbI3) has gained significant attention due to similar electronic and optical properties to methylammonium lead iodide (MAPbI3), with a band gap of 1.7 eV, high absorption coefficient, and large diffusion length, while also offering the advantage of being completely inorganic, providing a higher thermal stability and preventing material degradation. On a device level, however, it seems also essential to replace organic transport layers by inorganic counterparts to further prevent degradation. In addition, devices are mostly fabricated by spin coating, limiting their reproducibility and scalability; in this case, exploring all-evaporated devices allows us to improve the quality of the layers and to increase their reproducibility. In this work, we focus on the deposition of CsPbI3 by CsI and PbI2 co-evaporation. We fabricate devices with an all-inorganic, all-evaporated structure, employing NiO and TiO2 as transport layers, and evaluate these devices for both photodetector and solar cell applications. As a photodetector, low leakage current, high external quantum efficiency (EQE) and detectivity, and fast rise and decay times were obtained, while as a solar cell, acceptable efficiencies were achieved. These all-inorganic, all-evaporated devices represent one step forward toward higher stability and reproducibility while enabling large area compatibility and easier integration with other circuitry and, in future, the possible commercialization of perovskite-based technology. ispartof: ACS Applied Electronic Materials vol:3 issue:7 pages:3023-3033 ispartof: location:United States status: Published online

Image sensors are must-have components of most consumer electronics devices. They enable portable camera systems, which find their way into billions of devices annually. Such high volumes are possible thanks to the complementary metal-oxide semiconductor (CMOS) platform, leveraging wafer-scale manufacturing. Silicon photodiodes, at the core of CMOS image sensors, are perfectly suited to replicate human vision. Thin-film absorbers are an alternative family of photoactive materials, distinguished by the layer thickness comparable with or smaller than the wavelength of interest. They allow design of imagers with functionalities beyond Si-based sensors, such as transparency or detectivity at wavelengths above Si cutoff (e.g., short-wave infrared). Thin-film image sensors are an emerging device category. While intensive research is ongoing to achieve sufficient performance of thin-film photodetectors, to our best knowledge, there have been few complete studies on their integration into advanced systems. In this paper, we will describe several types of image sensors being developed at imec, based on organic, quantum dot, and perovskite photodiode and show their figures of merit. We also discuss the methodology for selecting the most appropriate sensor architecture (integration with thin-film transistor or CMOS). Application examples based on imec proof-of-concept sensors are demonstrated to showcase emerging use cases.

The next generation of tunable photonics requires highly conductive and light inert interconnects that enable fast switching of phase, amplitude, and polarization modulators without reducing their efficiency. As such, metallic electrodes should be avoided, as they introduce significant parasitic losses. Transparent conductive oxides, on the other hand, offer reduced absorption due to their high bandgap and good conductivity due to their relatively high carrier concentration. Here, we present a metamaterial that enables electrodes to be in contact with the light active part of optoelectronic devices without the accompanying metallic losses and scattering. To this end, we use transparent conductive oxides and refractive index matched dielectrics as the metamaterial constituents. We present the metamaterial construction together with various characterization techniques that confirm the desired optical and electrical properties.

High voltage cathodes suffer from degradation phenomena that are challenging to be observed and identified during cell operation. Dense and smooth sputtered thin films electrodes with absence of binders and conductive additives allow a direct study of the active material upon Li insertion and extraction at surface and bulk. Using an operando spectroscopic ellipsometry set-up combined with a customized electrochemical-optical cell (EC-SE), the evolution of the optical absorption and thickness of LiMn2O4 and LiNi0.5Mn1.5O4 thin-film electrodes was monitored upon cycling. Mixed Mn3+/4+ valence in the electrodes and evident layer dissolution associated to Transition Metal (TM) dissolution in the non-aqueous electrolyte at the applied polarization potentials was observed. Our results reaffirm EC-SE as a convenient method to study degradation phenomena in cobalt-free transition metal oxide electrodes.

Perovskite solar cells (PSCs) are among the most promising emerging photovoltaic technologies, demonstrating power conversion efficiencies (PCEs) close to 24%. The major challenge hampering commercialization of this technology is the low stability toward inevitable stress factors of PV modules such as temperature variations. Temperature variations are reported to induce a decline in photocurrent of up to 80%, depending on the device architecture, the charge transport layers, and the perovskite absorber material. The effect is particularly pronounced in methylammonium lead iodide-based PSCs, with TiO2 as the electron transport layer (ETL) and spiro-MeOTAD as the hole transport layer (HTL). This article reports on three different strategies to overcome the temperature-variation-induced degradation by altering the interfaces. The charge selective transport layers, the perovskite absorber layer composition, and the perovskite deposition technique are varied. We find that the interface between the ETL and the perovskite layer is the key to temperature-variation-induced degradation. We demonstrate stable PSCs with regard to temperature variations with PCEs as high as 19.5%. Finally, the relevance of the temperature-variation-induced degradation for outdoor applications is shown by stressing PSCs with real outdoor temperature profiles (between 21 and 75 °C).

The black perovskite phase of CsPbI

Device optimization of light-emitting diodes targets the most efficient conversion of electrically injected charges into emitted light. Where charges recombine and where light is emitted from is known as the emission zone. Determining its form is key to better understanding the physical processes determining device performance. However, a thorough measurement study has not been shown. Here we present an accessible technique to visualize the emission zone in unprecedented detail at all luminescing current densities. Only a single emission spectrum must be measured (at normal direction to the device layers with no additional optics) and compared with the simulated emission spectrum. This method allows physical understanding based, instead of speculative, optimisation of LED device architectures. We demonstrate its impact by examining the device structure – emission zone – lifetime relationships of a thermally activated delayed fluorescence OLED to achieve an ultralong 4500 hour T95 lifetime at 1000 cd/m2 with 20% external quantum efficiency.

Device optimization of light-emitting diodes (LEDs) targets the most efficient conversion of electrically injected charges into emitted light. The emission zone in an LED is where charges recombine and light is emitted from. It is believed that the emission zone is strongly linked to device efficiency and lifetime. However, the emission zone size is below the optical diffraction limit, so it is difficult to measure. An accessible method based on a single emission spectrum that enables emission zone measurements with sub-second time resolution is shown. A procedure is introduced to study and control the emission zone of an LED system and correlate it with device performance. A thermally activated delayed fluorescence organic LED emission zone is experimentally measured over all luminescing current densities, while varying the device structure and while ageing. The emission zone is shown to be finely controlled by emitter doping because electron transport via the emitter is the charge-transport bottleneck of the system. Suspected quenching/degradation mechanisms are linked with the emission zone changes, device structure variation, and ageing. Using these findings, a device with an ultralong 4500 h T95 lifetime at 1000 cd m-2 with 20% external quantum efficiency is shown. ispartof: ADVANCED MATERIALS vol:34 issue:29 ispartof: location:Germany status: published

ispartof: ADVANCED OPTICAL MATERIALS vol:10 issue:15 status: published

The coming of age of AR, VR and MR applications and usage scenarios relies on the development of ever-improved advanced light management systems, both for sensing (camera) and actuation (display), e.g., solid-state dToF or FMCW scanning or flash LiDAR, polarimetric imaging or resettable structured light illumination for 3D mapping, directional imager for light field registration, plasmonic or dielectric color filters and directors for efficient spectroscopic information acquisition. Indeed, optics remains the dominant user interface modality while large portions of required information can be retrieved in optical domain. These systems rely on the emergence of mature mass-manufacturing integrated photonics platforms in near infrared and visible wavelength ranges. This presentation introduces developments at imec of diffractive components for reflective, transmissive and guided applications on opaque (Si/CMOS) and transparent (quartz) substrates, relying on sub-wavelength nano-patterning techniques (from DUV dry and wet (immersion) lithography through 200mm wafer-scale e-beam, nano-imprint lithography, block-co-polymer to EUV), novel CMOS-compatible material toolbox beyond Si and SiN (passive, active, resettable and tunable) and high-aspect ratio re-filling to enable stacking of optical features to define complex functional system. In particular, we will report on pixel-integrated Fresnel phase plates for local eQE optimization, on process complexity trade-off enabled by optical meta-materials, aspherical and non-cylindrical optical components for directed light, tunable structured light scanners, plasmonic and dielectric-based color filters and directors, optical beamformer in near infrared, sub-wavelength spatial light modulator in the visible and finally novel developments for 2D optical waveguides.

Following the rapid increase of organic metal halide perovskites toward commercial application in thin-film solar cells, inorganic alternatives attracted great interest with their potential of longer device lifetime due to the stability improvement under increased temperatures and moisture ingress. Among them, cesium lead iodide (CsPbI

ispartof: ADVANCED OPTICAL MATERIALS vol:9 issue:15 status: published

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.

We provide insight into the driving mechanisms and requirements to create an electro-optic spatial light modulator based on a Barium Titanate waveguide and an optically transparent electrode cladding layer. This cladding is made from alternating pillars of transparent conductive oxides and index matched dielectrics. We have developed a generic framework of electric field simulations and non-linear optics to create any desired modulation in an area of interest, applicable for liquid crystals, Pockels and Kerr cells. Targeting our device structure, we have evaluated several design parameters of the arbitrarily reprogrammable SLM, capable of optical beamforming and high-quality holograms. ispartof: Proceedings Volume 11484, Optical Modeling and Performance Predictions XI; 114840D (2020) vol:11484 ispartof: Proc SPIE :Optical Modeling and Performance Predictions XI location:(online only) date:24 Aug - 4 Sep 2020 status: Published online

The reproducibility of results is one of the corner stones 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 (PCE) 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, we show 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, we propose a method based on pulsed excitation that allows better reproducibility and interpretation of the measured device characteristics. Furthermore, we also provide suggestions on reporting PeLED characteristics, as input for further discussions in the scientific community. ispartof: Advanced Optical Materials vol:8 issue:23 status: Published online

Capacitive touchscreens are increasingly widespread, featuring in mobile phones and tablets, as well as everyday objects such as cars and home appliances. As a result, the interfaces are uniquely placed to provide a means of communication in the era of the Internet of Everything. Here we show that commercial touchscreens can be used as reader interfaces for capacitive coupled data transfer. The transfer of data to the touchscreen is achieved using a 12-bit thin-film capacitive radio frequency identification tag powered by a thin-film battery or a thin-film photovoltaic cell that converts light from the screen. The thin-film integrated circuit has a 0.8 cm2 on-chip monolithic antenna, employs 439 transistors, and dissipates only 31 nW of power at a supply voltage of 600 mV. The chip has an asynchronous data rate of up to 36 bps, which is limited by the touchscreen readout electronics. ispartof: NATURE ELECTRONICS vol:2 issue:12 pages:606-611 ispartof: location:England status: published

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 cm2 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.

© 2018 The Royal Society of Chemistry. Perovskite-silicon tandem solar cells are potentially attractive, inexpensive solutions to surpass the power conversion efficiency limits of market-leading silicon solar cells. While such tandem solar cells have been demonstrated to reach high efficiencies, they require advanced light management to utilise the solar spectrum efficiently. Moreover, area upscaling with minimal optical losses is necessary to transfer the properties of lab scale devices to commercial scale products. Here, we demonstrate four-terminal perovskite-silicon tandem solar modules with efficient light management. With rigorous optical simulations of the complete tandem stack, we design light management concepts that minimise overall reflection and enhance complementary absorption of the subcells. The optical optimisation results in four-terminal tandem power conversion efficiencies of 25.3% on 0.13 cm2 and 23.9% on 4 cm2, both exceeding the stand-alone silicon solar cell power conversion efficiency of 23.0%. ispartof: ENERGY & ENVIRONMENTAL SCIENCE vol:11 issue:6 pages:1489-1498 status: published

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.

This paper reports on the analysis and comparison of mechanical and laser patterning in the fabrication of perovskite thin-film photovoltaic modules. Besides stability, device upscaling and module fabrication is a key challenge for the commercialization of perovskite photovoltaics. Here, the focus is on the optimization of the P2 interconnection that represents the electrical connection between serially connected cells in a module. The specific contact resistivity for P2 interconnection is determined by using an enhanced transmission line method. Mechanical or laser patterning are used to fabricate 4 cm $^{2}$ modules with aperture area efficiencies of up to 15.3% and geometrical fill factors as high as 94%. With the application of a simulation program with an integrated circuit emphasis-based electrical device model, the interconnection losses are quantified, and optimal designs for perovskite modules are presented.

All-thin film perovskite/CIGS multijunction solar modules, combining a semi-transparent perovskite top solar module stacked on a CIGS bottom solar module, are a promising route to surpass the efficiency limits of single-junction thin-film solar modules. In this work, we present a scalable thin-film perovskite/CIGS photovoltaic module with an area of 3.76 cm2 and a power conversion efficiency of 17.8%. Our prototype outperforms both the record single-junction perovskite solar module of the same area as well as the reference CIGS solar module. The presented perovskite/CIGS thin-film multijunction solar module makes use of the “4-terminal architecture”, which stacks the perovskite solar module in superstrate configuration on top of the CIGS solar module in substrate configuration. Both submodules apply a scalable interconnection scheme that can accommodate scale-up towards square meter scale thin-film multijunction solar modules. In order to identify the future potential of the presented stacked perovskite/CIGS thin-film solar module, we quantify the various losses in the presented prototype and identify the key challenges of this technology towards very high power conversion efficiencies.

Commercially available phenyl-C61-butyric acid methyl ester (PCBM) is crosslinked with 1,6-diazidohexane (DAZH), resulting in films resistant to common solvents used in perovskite solar cell processing. By using crosslinked PCBM as an interlayer and (HC(NH2)2)0.66(CH3NH3)0.34PbI2.85Br0.15 as the active layer, we achieve small area devices and modules with a maximum steady-state power conversion efficiency of 18.1% and 14.9%, respectively.

Low-cost solar technologies such as perovskite solar cells are not only required to be efficient, but durable too, exhibiting chemical, thermal and mechanical stability. To determine the mechanical stability of perovskite solar cells, the fracture resistance of a multitude of solution-processed organometal trihalide perovskite films and cells utilizing these films were studied. The influence of stoichiometry, precursor chemistry, deposition techniques, and processing conditions on the fracture resistance of perovskite layers was investigated. In all cases, the perovskites offered negligible resistance to fracture, failing cohesively below 1.5 J/m2. The solar cells studied featured these perovskites and a variety of organic and inorganic charge transporting layers and carrier-selective contacts. These ancillary layers were found to significantly influence the overall mechanical stability of the perovskite solar cells and were repeatedly the primary source of mechanical failure, failing at values below those measured for the isolated fragile perovskite films. A detailed insight into the nature of perovskite and perovskite solar cell fracture is presented and the influence of grain size, device architecture, deposition techniques, environmental variables, and molecular additives on these fracture processes is reported. Understanding the influence of materials selection, deposition techniques and processing variables on the mechanical stability of perovskite solar cells is a crucial step in their development.

ispartof: PROGRESS IN PHOTOVOLTAICS vol:27 issue:8 pages:733-738 status: published

With the realization of highly efficient perovskite solar cells, the long-term stability of these devices is the key challenge hindering their commercialization. In this work, we study the temperature-dependent stability of perovskite solar cells and develop a model capable of predicting the lifetime and energy yield of perovskite solar cells outdoors. This model results from the measurement of the kinetics governing the degradation of perovskite solar cells at elevated temperatures. The individual analysis of all key current-voltage parameters enables the prediction of device performance under thermal stress with high precision. An extrapolation of the device lifetime at various European locations based on historical weather data illustrates the relation between the laboratory data and real-world applications. Finally, the understanding of the degradation mechanisms affecting perovskite solar cells allows the definition and implementation of strategies to enhance the thermal stability of perovskite solar cells. ispartof: ACS APPLIED MATERIALS & INTERFACES vol:11 issue:18 pages:16517-16526 ispartof: location:United States status: published

To guarantee a long lifetime of perovskite-based photovoltaics, the selected materials need to survive relatively hightemperature stress during the solar cell operation. Highly efficient ni-p perovskite solar cells (PSCs) often degrade at high operational temperatures due to morphological instability of the hole transport material 2,2',7,7'-tetrakis (N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (Spiro-OMeTAD). We discovered that the detrimental large-domain spiro-OMeTAD crystallization is caused by the simultaneous presence of tert-butylpyridine (tBP) additive and gold (Au) as a capping layer. Based on this discovery and our understanding, we demonstrated facile strategies that successfully stabilize the amorphous phase of spiro-OMeTAD film. As a result, the thermal stability of n- i-p PSCs is largely improved. After the spiro-OMeTAD films in the PSCs were stressed for 1032 h at 85 degrees C in the dark in nitrogen environment, reference PSCs retained only 22% of their initial average power conversion efficiency (PCE), while the best target PSCs retained 85% relative average PCE. Our work suggests facile ways to realize efficient and thermally stable spiro-OMeTAD containing n-i-p PSCs. European Union's H2020 Program for research, technological development, and demonstration [764047]; Kuwait Foundation for the Advancement of Sciences [CN18-15EE-01]; Research Foundation.Flanders (FWO)[G031416N]

Hybrid metal-halide perovskite-based thin-film photovoltaics (PVs) have the potential to become the next generation of commercialized PV technology with certified power conversion efficiencies reaching 24% on devices having 0.1 cm(2) area. Recent efforts in upscaling this technology result in an efficiency of 12.6% for 354 cm(2) modules. However, upscaling loss for perovskite-based PVs is higher than for any other PV technology. In this study, upscaling losses of devices with aperture area 0.1, 4, and 100 cm(2) are investigated, with a focus on layer inhomogeneities. Electroluminescence, dark lock-in thermography, microphotoluminescence spectroscopy, and electron spectroscopy are used to analyze and group layer inhomogeneities with a minimal size of 10 mu m and to compare loss mechanisms for radial and linear deposition techniques. Analysis results help to identify current processing pitfalls, where understanding and control of perovskite crystal formation plays the crucial role.

We report on a perovskite solar module with an aperture area of 4 cm2 and geometrical fill factor of 91%. The module exhibits an aperture area power conversion efficiency (PCE) of 13.6% from a current–voltage scan and 12.6% after 5 min of maximum power point tracking. High PCE originates in pinhole-free perovskite films made with a precursor combination of Pb(CH3CO2)2·3H2O, PbCl2, and CH3NH3I.

The scaling of thin film photovoltaics to a commercially viable size relies on the series connection of multiple small cells into modules. These interconnections are typically formed by three patterning steps, each of which have an impact on the series resistance and consequently on the total module performance. Here, we implement the transmission line method for the complete analysis of the P2 patterning step of the photoactive layer in organic photovoltaic modules. Devices are investigated with a sample design that allows for a comparative study of the P2 connection on the solar cell performance. We compare subtractive mechanical scribing to a newly developed additive pre-patterning method for the P2 step. Aerosol Jet printed pre-patterning lines of low surface energy and conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) modified with a fluorosurfactant repel the subsequently spray coated photoactive layer. Furthermore, the influence of MoO3 in the P2 pattern is elucidated, displaying a substantial increase in series resistance and decrease in device performance.

Recently, large area hybrid silicon heterojunction cells (SHJ) with nickel/copper (Ni/Cu) plated front contacts were shown to benefit from a simpler processing sequence than n-PERT cells featuring a boron diffused rear emitter. Hybrid refers here to the combination of a diffused front surface field (FSF) and a SHJ rear emitter. In this work, further process simplifications for such hybrid SHJ cells are evaluated. Based on reflectance and adhesion considerations, stacks of tin-doped indium oxide and copper (ITO/Cu) and chromium/silver (Cr/Ag) are tested as alternative to the previously chosen ITO/Ag rear contact stack. Using ITO/Cu/Al as rear contact stack, average efficiencies of 20.8±0.2% are presented on 6-inch wafers. We also demonstrate that the excimer laser annealing step previously employed to form nickel silicides at the front side can be skipped without comprising solder tab adhesion quality.

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. ispartof: GLOBAL CHALLENGES vol:2 issue:7 ispartof: location:Germany status: published

We present four-terminal perovskite-Si and perovskite-CIGS tandem solar modules that are fully scalable to commercial dimensions. Starting from small cells of 0.13 cm_2, we scale up the tandem devices by a factor of 30 to modules of 4 cm_2. By using a low-loss module design and optimized light coupling, we demonstrate perovskite-Si and perovskite-CIGS tandem solar modules which outperform the stand-alone devices on the large area, representing a key milestone for perovskite-based tandem photovoltaics. Moreover, the tandem solar module architecture is compatible with industrially scalable fabrication techniques, thus opening the route towards production of high-performance large-area perovskite-based tandem solar modules.

Perovskite solar cells (PSCs) are one of the most promising emerging photovoltaic technologies, demonstrating high efficiencies and low fabrication costs. This work reports on the stability of high-efficient PSCs stressed with realistic temperature variations. The photocurrent is found to reversibly decline below 20% of the initial value in the most common device architecture based on a TiO 2 electron transport layer, upon cycling the temperature between 10°C and 60°C. In contrast, the photocurrent stabilizes for constant temperatures. The degradation can be prevented by replacing the electron transport layer with more stable materials. Finally, the impact of this degradation for outdoor application is shown by stressing PSCs with a real outdoor temperature profile.

This paper reports on the impact of outdoor temperature variations on the performance of organo metal halide perovskite solar cells (PSCs). It shows that the open-circuit voltage (VOC) of a PSC decreases linearly with increasing temperature. Interestingly, in contrast to these expected trends, the current density (JSC) of PSCs is found to decline strongly below 20% of the initial value upon cycling the temperatures from 10 to 60 °C and back. This decline in the current density is driven by an increasing series resistance and is caused by the fast temperature variations as it is not apparent for solar cells exposed to constant temperatures of the same range. The effect is fully reversible when the devices are kept illuminated at an open circuit for several hours. Given these observations, an explanation that ascribes the temperature variation-induced performance decline to ion accumulation at the contacts of the solar cell because of temperature variation-induced changes of the built-in field of the PSC is...

© 2018 The Royal Society of Chemistry. Thin film perovskite photovoltaic devices combine high power conversion efficiencies with low weight, large area, high speed production capabilities and high versatility in form factor. With this paper, an additional feature is added to the device property portfolio: optical transparency. Results on translucent perovskite modules with selectively tuned levels of transparency are reported by applying the industrially established fabrication process of partial area ablation to high efficiency opaque devices. After process completion, the final devices consist of opaque areas that absorb the light, and transparent areas that permit neutral light transmission. We compare the effectiveness of using two active area removal techniques: mechanical scribing and laser ablation, and determine the factors that limit the maximum transparency and power conversion efficiency. Moreover, we show how the choice of the ablation method and design of the active area removal pattern affect and limit the maximum light utilization efficiency ratio that can be achieved with this fabrication process. The resulting 4 cm2 translucent modules cover a range of visible light transparency from 7 to 37% with a corresponding power conversion efficiency of 5 to 13%. ispartof: JOURNAL OF MATERIALS CHEMISTRY C vol:6 issue:12 pages:3034-3041 status: published

With lab-scale solution-processed thin fi lm photovoltaic (TFPV) devices attaining market relevant effi ciencies, the demand for environmentally friendly and scalable deposition techniques is increasing. Replacing toxic halogenated solvents is a priority for the industrialization of solution-processed TFPV. In this work, a generalized fi ve-step process is presented for fabricating high-performance devices from nonhalogenated inks. Resulting from this process, several new solvent systems are introduced based on thiophene, tetralin, 1,2,4-trimethylbenzene, o -xylene, and anisole for blade coating of three different diketopyrrolopyrrole-based (pDPP5T-2, pPDPP5T-2S, and P390) bulk heterojunctions applied in organic photovoltaic devices. Devices based on pDPP5T-2S and P390 attain 5.6% and 6.1% effi ciency, respectively, greater than the effi ciency either material reached when processed from the halogenated solvent system commonly used. These processes are implemented without post-deposition annealing treatments or additives. The Hansen solubility parameters of the pDPP5T-2 material are obtained, and are used, along with wettability data on a variety of substrates, to determine optimum solvent combinations and ratios for deposition. This generalized fi ve-step process results in new nonhalogenated solvent pathways for the scalable deposition of thin fi lm photovoltaic materials.

The TiO2 layer made by electron beam (e-beam) induced evaporation is demonstrated as an electron transport layer (ETL) in high efficiency planar junction perovskite solar cells. The temperature of the substrate and the thickness of the TiO2 layer can be easily controlled with this e-beam induced evaporation method, which enables the usage of different types of substrates. Here, perovskite solar cells based on CH3NH3PbI3−xClx achieve power conversion efficiencies of 14.6% on glass and 13.5% on flexible plastic substrates. The relationship between the TiO2 layer thickness and the perovskite morphology is studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Our results indicate that the pinholes in the thin TiO2 layer lead to pinholes in the perovskite layer. By optimizing the TiO2 thickness, perovskite layers with substantially increased surface coverage and reduced pinhole areas are fabricated, increasing overall device performance.