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We report on the improved operational stability of unencapsulated perovskite solar cells (PSCs) aged in ambient atmosphere at elevated temperatures (70 C) for >1000 hours under constant illuminati...

Towards scalable manufacturing of perovskite solar panels, high-performance planar p-i-n perovskite solar cells (PVSCs) and modules have been demonstrated with blade-coating and rapid thermal proce...

Low-bandgap Sn/Pb ABX3 perovskites have reached photovoltaic power conversion efficiencies >20%, but they usually have poor stability due to the common use of acidic poly(3,4-ethylenedioxythiophene...

Tuning band gaps with three halides Tandem solar cells can boost solar cell efficiency by using two active layers to absorb the solar spectrum more completely, provided that the two cells are current-matched. Inorganic-organic perovskites tuned to the appropriate wide band gap (∼1.7 electron volts) as top cells that contained iodine and bromine or bromine and chlorine have short carrier diffusion lengths and undergo photo-induced phase segregation. Xu et al. now report a method for incorporating chloride that allows for fabrication of stable triple-halide perovskites with a band gap of 1.67 electron volts. Two-terminal tandem silicon solar cells made with this material had a power conversion efficiency of 27%. Science , this issue p. 1097

Tandem or multijunction solar cells are able to convert sunlight to electricity with greater efficiency than single junction solar cells by splitting the solar spectrum across sub-cells with different bandgaps. With the efficiencies of many common single-junction solar cell materials leveling off near their theoretical efficiency limits, there is renewed interest in applying this approach. However, there is ongoing debate as to the best approach for interconnecting sub-cells in series, or whether it is preferable to operate them independently. In this paper, we provide the first experimental demonstration of a tandem cell architecture with three terminals: one on top of the tandem cell, and two beneath it, in interdigitated back contact configuration. The two cells are interconnected with a transparent conductive adhesive, which is compatible with rough surfaces and exhibits negligible series resistance. Combining GaInP and Si sub-cells in this manner allows us to achieve a GaInP/Si tandem cell with a two-terminal efficiency of 26.4 ± 1.0%. We then show that utilizing all three terminals results in an efficiency boost of 0.9 ± 0.2%, to an efficiency of 27.3 ± 1.0%, and discuss the operation of the cell and its two interacting circuits.

Perovskite solar cells have now become the most efficient of all multicrystalline thin film photovoltaic technologies, reaching 25.2% in 2019. This outstanding figure of merit has only been achieved on small lab-scale devices, with significantly lower performance when processed on larger more industrially relevant substrate sizes. Perovskite modules, connecting several smaller area cells together, are commonly demonstrated with a superstrate monolithic interconnection method. However, several other module designs exist and remain largely unexplored by the perovskite community. In this work, we review and highlight those alternatives and discuss their advantages and limitations. We propose that a singulated substrate-oriented module design, using metallic substrates, could provide a quicker path to seeing highly efficient, lightweight, and flexible perovskite modules on the market, while mitigating near-term technical risks. As an experimental starting-point towards this design, we demonstrate a substrate-oriented all-perovskite 2-terminal tandem with 18% efficiency.

Summary Realizing photovoltaic devices that achieve the full potential of the metal halide perovskite material will require improved insight regarding the role of selective contacts and how key interfaces operate when mobile defects are present. However, measuring interface properties in typical device stacks where the perovskite layer is thin and sandwiched between two contacts has been a challenge. Here, we fabricate p-i-n and p-n lateral heterojunctions with nickel oxide/titanium oxide all back contacts, permitting us to employ a comprehensive analysis approach, including ultraviolet and X-ray photoemission spectroscopy (UPS/XPS), angle-resolved X-ray absorption spectroscopy (XAS), Kelvin probe force microscopy (KPFM), surface photovoltage (SPV), hyperspectral imaging (HSI), and time-resolved fluorescence lifetime imaging microscopy (TR-FLIM) to discern the role of selective contacts. Specifically, we tune the selectivity of the contacts, changing the gradient in the carrier concentration across the surface of the active layer, which is connected to carrier extraction at the buried interface, and thus the device functionality.

In this work, we fabricated halide perovskite-based lateral heterojunction devices with nickel oxide/titanium oxide all back contacts, allowing us to access the perovskite surface directly for analysis with various advanced techniques, including ultraviolet and X-ray photoemission spectroscopy (UPS/XPS), Kelvin probe force microscopy (KPFM), and surface photovoltage (SPY), to discern the role of selective contacts. Specifically, by tuning of the selectivity of the contacts, e.g., through varying the level of nickel oxidation, we show that the selectivity of the contacts induces a gradient in carrier concentration across the surface of the active layer that is connected to carrier extraction at the buried interface and hence to device functionality.

This research is focused on the development of a thermally stable perovskite cell designed for operation in space. We describe the methodology used to test both perovskite cells and component materials, in preparation for eventual space qualification.

Summary Multijunction all-perovskite solar cells offer a route toward efficiencies of III-V materials at low cost by combining the advantages of low thermalization loss in multijunction architectures with the beneficial properties of perovskites—namely, low processing cost, high-throughput fabrication, and compatibility with flexible substrates. However, there are two main challenges for enabling high-efficiency tandems: (1) design of a recombination layer to efficiently combine two perovskite subcells while also preventing bottom cell damage during top cell processing and (2) achieving high open-circuit voltage of the wide-gap subcell. Herein, we overcome both of these challenges. First, we demonstrate a nucleation layer consisting of an ultra-thin polymer with nucleophilic hydroxyl and amine functional groups for nucleating a conformal, low-conductivity aluminum zinc oxide layer by atomic layer deposition (ALD). This method enables ALD-grown recombination layers that reduce shunting as well as solvent degradation from solution processing on top of existing perovskite active layers. Next, we demonstrate a band-gap tuning strategy based on A-site cations of mismatched size (dimethylammonium and cesium) to enable a 1.7 eV perovskite with high, stable voltages. By combining these advances, we fabricate two-terminal all-perovskite tandem solar cells with 23.1% power conversion efficiency on rigid substrates and 21.3% on flexible plastic substrates.

Band offsets at the back contact and front window layer in CdTe-based solar cells affect photovoltaic performance and challenge standard characterization methods. By analyzing the temperature and excitation dependence of both open circuit voltage and absolute photoluminescence intensity, we show that the effects band offsets can be separated from the effects of recombination and shunting. Solar cells were grown with MgZnO window layers and compared to cells with CdS window layers containing varying amounts of oxygen. It was demonstrated that band alignment rather than reduced recombination velocity is the reason for the success of MgZnO as a front interface contact. An assortment of thin back contact interlayers were also deposited, and a PbTe interlayer showed some promise as an Ohmic contact to the CdTe, though it appears to induce a photoconductive shunt. Finally, we show that the shunting resistance given by a standard current-voltage curve technique generally does not represent a physically meaningful quantity unless it is well below one kiloOhm square cm.

Summary Tandem solar cells coupling narrow- and wide-band-gap thin-film polycrystalline absorbers are attractive for achieving ultrahigh efficiency with low manufacturing cost. For established narrow-band-gap CIGS thin-film bottom cells, a challenge is to develop highly efficient polycrystalline wide-band-gap top cells. Here, we demonstrate a 1.68-eV (FA0.65MA0.20Cs0.15)Pb(I0.8Br0.2)3 wide-band-gap perovskite solar cell with an efficiency of ∼20% enabled by using PEAI and Pb(SCN)2 complementary additives in the perovskite precursor. The coupling of PEA+ and SCN− provides a synergistic effect that overcomes growth challenges with either additive individually and improves perovskite film quality with enhanced crystallinity, reduced formation of excess PbI2 (in comparison to using Pb(SCN)2 additive alone), lower defect density and energetic disorder, and an improved carrier mobility (∼47 cm2 V−1s−1) and lifetime (∼2.9 μs). When coupling a semi-transparent 1.68-eV perovskite top cell fabricated by this approach with a 1.12-eV CIGS bottom cell, we achieve 25.9%-efficient polycrystalline perovskite/CIGS 4-terminal thin-film tandem solar cells.

Efficient all-perovskite tandem cells Organic-inorganic perovskite films can boost the output of conventional silicon solar cells in tandem geometries by utilizing more of the light at the blue end of the solar spectrum. Tandem cells that use only perovskite films have been less successful because of the lack of a suitable material with a low bandgap that can replace silicon. Tong et al. report that a mixed tin-lead organic-inorganic material containing a small fraction of guanidinium thiocyanate has a low bandgap, long charge-carrier lifetime, and efficiencies around 25%. Science , this issue p. 475

Achievement of high conductivity by doping an oxide thin film while maintaining its high visible transparency remains a challenge in the field of materials science and technology. Here, we demonstrate a simple and novel technique to control compensating defects in Al doped ZnO (AZO) thin films involving a post-growth annealing process with Zn blanket. We also provide an in-depth understanding of the mechanism of achieving high conductivity. As low as 8.8 Ω/sq sheet resistance (resistivity 3.1 × 10−4 Ω cm) with 90% visible transmission value and wherefrom a figure of merit (FOM) value of 6.5 × 10−2 Ω−1 for a RF sputtered 350 nm AZO thin film can be achieved. Such very low sheet resistance has been attributed to a decrease in the number of compensating defects and lesser out diffusion of Zn in AZO. Application of the developed AZO film as conducting substrate has successfully been tested by fabricating perovskite solar cells on flexible Corning® Willow® Glass substrate. The present findings open up the possibility of enough high quality industrial-scale production of transparent conducting oxides (TCOs) bearing crucial significance from the perspective of transparent electrodes for solar cells.

Summary Cost modeling shows that high-throughput processing of perovskite solar cells is required not only to compete with incumbent technologies in terms of levelized cost of energy, but more importantly, it is the major enabling factor facilitating sustainable growth rates of solar cell manufacturing capacity commensurate with global climate targets. We performed rapid thermal annealing at blade-coating speed to quickly deposit and convert perovskite thin films for scalable manufacturing of perovskite solar cells. In situ X-ray diffraction during film deposition and thermal conversion gave insight into the formation of crystalline intermediates, essential for high-quality films. Parameters were optimized based on the in situ study, allowing perovskite films to be annealed within 3 s with a champion power conversion efficiency of 16.8%. This opens up a clear pathway toward industrial-scale high-throughput manufacturing, which is required to fulfill the projected photovoltaic installation rates needed to reach climate goals.

Perovskite solar technology can produce economically viable photovoltaic devices due to low cost of materials and scalable manufacturing. Solution phase deposition of all active layers lends itself to roll-to-roll fabrication methods which are well-established and have production rates of several hundred square meters per minute. In this techno-economic analysis, the opportunity to scale at this production throughput is considered with manufacturing rates exceeding one gigawatt per year in a single plant. Intense pulsed light is used for the post deposition process to minimize costs associated with the footprint, equipment, and operation. The analysis is limited to the operation of a roll-to-roll manufacturing facility producing a perovskite solar film that can be incorporated into photovoltaic modules. Costs associated with materials, labor, and equipment are considered along with utilities determined from the fundamental engineering calculations. The results show that at very large-scale operations of several gigawatts, the costs to produce the solar films range between $0.04 and $0.10 per watt.

Perovskite thin films are currently fabricated via solution-processible methods that rapidly deposit perovskite inks; however, annealing perovskite thin films remains a bottleneck in the manufacturing process. A combination of different methods to reduce requisite time for perovskite film formation while simultaneously protecting temperature sensitive plastic substrates are needed to make flexible PSCs at scale. Here, we introduce a blade coated perovskite thin film annealed via a two-step staggered rapid thermal annealing (RTA) for 7 seconds yielding PSCs with a PCE of 14.6% on flexible ITO/PET. This study demonstrates the advantages of RTA over conventional conductive annealing when manufacturing temperature-sensitive, flexible PSCs.

With the rapid improvements in performance of perovskite photovoltaics, scale represents one of the few remaining hurdles to commercial viability. The active perovskite layer has previously been deposited via a scalable solution-based method, blade coating. Associated transport layers, however, are often deposited using energy- and capital-intensive methods. Here, we present processes by which the electron transport layer, a mixed fullerene solution, and cathode buffer layer, bathocuproine, are blade-coated in an ambient environment to fabricate large-area solar devices that match or outperform the equivalent film deposited via thermal evaporation. With this work, a high-performing, scalable perovskite solar cell can be manufactured in ambient conditions from top to bottom contact.

High efficiency combined with transformative roll-to-roll (R2R) printability makes metal halide perovskite-based solar cells the most promising solar technology to address the terawatt challenge of the future energy demand. However, translation from lab-scale deposition solution processing techniques to large-scale R2R methods has typically led to reduced photovoltaic performance. Here, we demonstrate large-scale, highly crystalline, uniaxially oriented, smooth perovskite films printed at room temperature and in the ambient environment. Confirmed with high speed in situ X-ray diffraction measurements, the perovskite films reach 98% of relative crystallinity at room temperature and display high texture within 1 s of the coating. We demonstrate an all-blade-coated metal halide perovskite cell with power conversion efficiency (PCE) up to 19.6%, a slot-die coated cell with a PCE of 17.3%, and a partially R2R slot-die coated flexible glass-based cell efficiency of 14.1%. The developed printing method can be ap...

Rapid development of perovskite solar cells (PSCs) during the past several years has made this photovoltaic (PV) technology a serious contender for potential large-scale deployment on the terawatt scale in the PV market. To successfully transition PSC technology from the laboratory to industry scale, substantial efforts need to focus on scalable fabrication of high-performance perovskite modules with minimum negative environmental impact. Here, we provide an overview of the current research and our perspective regarding PSC technology toward future large-scale manufacturing and deployment. Several key challenges discussed are (1) a scalable process for large-area perovskite module fabrication; (2) less hazardous chemical routes for PSC fabrication; and (3) suitable perovskite module designs for different applications.

Selenization, sulfurization, and sulfo-selenization of electrodeposited metal precursor (Cu–Sn–Zn) at high temperature (500–600 °C) in S, Se, or S + Se (mixed) atmospheres are used to understand the thermodynamics of chalcogenide incorporation reaction. Phase-pure CZTSe and CZTS were obtained after annealing at 500 °C for 1 min in Se (selenization) and 600 °C for 10 min in S (sulfurization) atmospheres, respectively. CZTSSe solid solutions are synthesized by the sequential annealing of metal precursors in S and Se atmosphere separately or in the mixed (S + Se) atmosphere. In the S-rich mixed atmosphere, S-rich CZTSSe solid solution is formed at all annealing conditions. Surprisingly, in a Se-rich mixed atmosphere, longer annealing at 600 °C yields S-rich CZTSSe. The CZTSSe film formed by annealing in near equimolar S/Se atmosphere exhibits a compositional gradient across the thickness. These results suggest that the crystallinity, composition, and hence the bandgap of CZTSSe can be precisely controlled by...

Standard layer-by-layer solution processing methods constrain lead–halide perovskite device architectures. The layer below the perovskite must be robust to the strong organic solvents used to form the perovskite while the layer above has a limited thermal budget and must be processed in nonpolar solvents to prevent perovskite degradation. To circumvent these limitations, we developed a procedure where two transparent conductive oxide/transport material/perovskite half stacks are independently fabricated and then laminated together at the perovskite/perovskite interface. Using ultraviolet–visible absorption spectroscopy, external quantum efficiency, X-ray diffraction, and time-resolved photoluminesence spectroscopy, we show that this procedure improves photovoltaic properties of the perovskite layer. Applying this procedure, semitransparent devices employing two high-temperature oxide transport layers were fabricated, which realized an average efficiency of 9.6% (maximum: 10.6%) despite series resistance l...

Whereas the promise of metal halide perovskite (MHP) photovoltaics (PV) is that they can combine high efficiency with solution-processability, the chemistry occurring in precursor inks is largely unexplored. Herein, we investigate the degradation of MHP solutions based on the most widely used solvents, dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). For the MHP inks studied, which contain formamidinium (FA+), methylammonium (MA+), cesium (Cs+), lead (Pb2+), bromide (Br–), and iodide (I–), dramatic compositional changes are observed following storage of the inks in nitrogen in the dark. We show that hydrolysis of DMF in the precursor solution forms dimethylammonium formate, which subsequently incorporates into the MHP film to compromise the ability of Cs+ and MA+ to stabilize FA+-based MHP. The changes in solution chemistry lead to a modification of the perovskite film stoichiometry, band gap, and structure. The solid precursor salts are stable when ball-milled into a powder, allowing for the storag...

We demonstrate the use of supersonic spraying for the deposition of silver nanowires (AgNWs) on a flexible polyimide (PI) substrate for the formation of transparent and conducting films (TCF) as an alternative to nonflexible ITO (indium tin oxide). The self-fused intersections of the NWs resulted in films with a low sheet resistance (Rs = 31 Ω/sq) and fairly high transmittance (Tr = 92%) on a glass substrate. The effect of the impact speed of the supersonically sprayed AgNWs on the opto-electric properties of the flexible TCF was evaluated by varying the spray coating conditions. The fabricated films were characterized by X-ray diffraction analysis, atomic force microscopy, ultraviolet–visible spectroscopy, and scanning electron microscopy. Finally, cyclic bending tests were performed on the PI/AgNW films as well as PI/ZnO/indium tin oxide/AgNW films, and the changes in their electrical properties with bending were compared.

To push perovskite solar cell (PSC) technology toward practical applications, large-area perovskite solar modules with multiple subcells need to be developed by fully scalable deposition approaches. Here, we demonstrate a deposition scheme for perovskite module fabrication with spray coating of a TiO2 electron transport layer (ETL) and blade coating of both a perovskite absorber layer and a spiro-OMeTAD-based hole transport layer (HTL). The TiO2 ETL remaining in the interconnection between subcells significantly affects the module performance. Reducing the TiO2 thickness changes the interconnection contact from a Schottky diode to ohmic behavior. Owing to interconnection resistance reduction, the perovskite modules with a 10 nm TiO2 layer show enhanced performance mainly associated with an improved fill factor. Finally, we demonstrate a four-cell MA0.7FA0.3PbI3 perovskite module with a stabilized power conversion efficiency (PCE) of 15.6% measured from an aperture area of ∼10.36 cm2, corresponding to an a...

Perovskite based photovoltaic devices hold the promise to greatly reduce the cost of solar energy production; however, this potential depends greatly on the ability to deposit perovskite active layers using large scale deposition methods such as slot-die coating without sacrificing efficiency. Using a perovskite precursor ink with long wet-film processing window, we demonstrate efficient perovskite solar cells based on slot-die coated perovskite layer. We found almost no difference in the photophysical and structural details of perovskite films that were deposited by spin coating to films deposited by slot-die coating. We explored various slot-die coating parameters to determine their effect on the performance of the device metrics. In addition to slot-die coating, we demonstrate the versatility of this wide wet-film processing window by fabricating perovskite solar cells with active layers deposited by spin coating, blade coating, and spray coating that all exhibited similar performance.

A series of nickel oxide (NiO x ) inks, in the perovskite antisolvent chlorobenzene (CB) containing 15% ethanol, were prepared for the fabrication of p-i-n perovskite solar cells by blade coating. The inks included triethylamine (Et3N) and alkyl xanthate salts as ligands to disperse NiO x particle aggregates and stabilize suspension. A total of four inks were evaluated: 0X (Et3N with no alkyl xanthate), 4X (Et3N + potassium n-butyl xanthate), 12X (Et3N + potassium n-dodecyl xanthate), and 18X (Et3N + potassium n-octadecyl xanthate). The inks were characterized by UV–visible spectroscopy and FT-IR spectroscopy and the resulting films analyzed by thermogravimetry and scanning electron microscopy. Devices prepared using the 0X ink resulted in a peak power conversion efficiency (PCE) of 14.47% (0.25 cm2) and 9.96% (1 cm2). The 0X devices showed no significant loss of PCE after 100 days in a nitrogen flow box. Devices prepared with inks containing alkyl xanthate ligand had lower PCE that decreased with decreasing chain length, 18X > 12X > 4X.

Organic–inorganic hybrid halide perovskites are one of the most promising emerging photovoltaic materials due to their high efficiency and potentially low processing cost. Here, we present a well-controlled, manufacturing relevant annealing method, radiative thermal annealing, for the methylammonium lead triiodide (MAPbI3) films formed by a solvent engineering process, with dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) as solvent and diethyl ether as the antisolvent. Radiative thermal annealing can produce high quality perovskite films, evidenced by high efficiency solar cell devices (∼18% power conversion efficiency), in a shorter time than the widely used hot plate annealing. Using in situ X-ray diffraction during the radiative annealing, we show that the role of the antisolvent is not to form an important intermediate compound (a PbI2-MAI-DMSO complex) by washing of the main solvent (DMF), but to achieve a pinhole free, uniform film of MAPbI3 with minimal intermediate compound. Importantly, we ...

Lead halide perovskites have emerged as successful optoelectronic materials with high photovoltaic power conversion efficiencies and low material cost. However, substantial challenges remain in the scalability, stability and fundamental understanding of the materials. Here we present the application of radiative thermal annealing, an easily scalable processing method for synthesizing formamidinium lead iodide (FAPbI3) perovskite solar absorbers. Devices fabricated from films formed via radiative thermal annealing have equivalent efficiencies to those annealed using a conventional hotplate. By coupling results from in situ X-ray diffraction using a radiative thermal annealing system with device performances, we mapped the processing phase space of FAPbI3 and corresponding device efficiencies. Our map of processing-structure-performance space suggests the commonly used FAPbI3 annealing time, 10 min at 170 °C, can be significantly reduced to 40 s at 170 °C without affecting the photovoltaic performance. The Johnson-Mehl-Avrami model was used to determine the activation energy for decomposition of FAPbI3 into PbI2. Processing is crucial to ensure material quality and stability in perovskite solar cells. Here, Poolet al. develop a scalable infrared annealing method and use in situXRD to map the processing phase space relative to the device efficiency. This provides a tool to determine processing requirements.

This work evaluates the critical issues surrounding P1, P2, and P3 scribing for semi-transparent perovskite module integration. We find that P1 scribing procedures are well-translated from other thin-film technologies. P2 scribing is best performed with a mechanical scribe, but remains a source of series resistance. P3 scribing is found to cause an increase in scribing dead area and a potential degradation source.

Integrating wide-bandgap III- V with Si solar cells has been shown to yield higher efficiencies than Si alone: As also presented at this conference, four-terminal efficiencies exceeding 32 % have been attained. In this contribution, independent and electrically connected operation of the subcells in such tandem cells is examined. The optics of the tandem cell change significantly if a conducting interconnect, rather than an insulating glass slide, is required between the subcells. These effects are studied, and optically optimized structures for different types of tandem cell operation are presented. It is found that minimizing reflection at the conductive interface between the two cells while maintaining conductivity is the key challenge faced in such devices.

Tin-lead perovskites have low band gaps (1.2 eV – 1.4 eV) that offer complementary absorption spectra to mixed halide perovskites with band gaps in the range of 1.6 eV – 1.85 eV. In combination, tin-lead and mixed halide perovskites can be used to make efficient all-perovskite tandem solar cells. While these can achieve high efficiency, they are hampered by the unproven longterm stability of tin-containing perovskites. We make the first demonstration of tin-lead perovskite solar cells that pass benchmark 1000-hour tests of stability under stressors of heat, light, and atmospheric exposure. We identify that mixed tin-lead perovskites oxidise by a different chemical pathway, one that is much less favourable, than the oxidation pathway followed by pure tin perovskites, making them significantly more stable. Fortuitously, mixed tin-lead perovskites also have band gaps that are close to ideal for the rear cell of an all-perovskite monolithic two-junction tandem. Beyond selecting the composition of the perovskite to be one that has inherently suppressed tendency to oxidise, we also fabricate a novel heterojunction-based architecture that eliminates the commonly used acidic PEDOT:PSS layer, which leads to enhanced stability. By packaging the resulting solar cell in a glass-on-glass package with a pliable low-elastic-modulus polyolefin encapsulant and a butyl rubber edge seal, we also demonstrate that the low band gap perovskite solar cell that passes the IEC damp heat test for thin film solar cells – a milestone that demonstrates the removal of a significant impediment to the commercialization of high efficiency perovskite tandem solar cells.

Contact layers play an important role in thin film solar cells, but new material development and optimization of its thickness is usually a long and tedious process. A high-throughput experimental approach has been used to accelerate the rate of research in photovoltaic (PV) light absorbers and transparent conductive electrodes, however the combinatorial research on contact layers is less common. Here, we report on the chemical bath deposition (CBD) of CdS thin films by combinatorial dip coating technique and apply these contact layers to Cu(In,Ga)Se-2 (CIGSe) and Cu2ZnSnSe4 (CZTSe) light absorbers in PV devices. Combinatorial thickness steps of CdS thin films were achieved by removal of the substrate from the chemical bath, at regular intervals of time, and in equal distance increments. The trends in the photoconversion efficiency and in the spectral response of the PV devices as a function of thickness of CdS contacts were explained with the help of optical and morphological characterization of the CdS thin films. The maximum PV efficiency achieved for the combinatorial dip-coating CBD was similar to that for the PV devices processed using conventional CBD. The results of this study lead to the conclusion that combinatorial dip-coating can be used to accelerate the optimization of PV device performance of CdS and other candidate contact layers for a wide range of emerging absorbers.

Adaptability, lightweight, and low cost of materials make flexible perovskite solar cells essential for the perovskite technology to breach commercial photovoltaic markets. Roll-to-roll manufacturing has great potential for high-throughput perovskite manufacturing; however, conventional annealing methods are not capable of producing flexible perovskite solar cells at scale. Conventional methods are time consuming and may compromise functionality of flexible substrates under tension. Here, we introduce a blade-coated perovskite thin film on flexible ITO-coated PET annealed via rapid thermal annealing (RTA) that reduces post-deposition processing time from ~150 s to ~14 s. Performance was not sacrificed for scalability as a perovskite solar cell was produced with a power conversion efficiency (PCE) of 14.58%.

We report scalable deposition of perovskite thin film by blade coating and slot-die coating towards large-area perovskite solar cell and module development. We find that extending perovskite ink processing window is critical to transitioning from laboratory-scale spin coating to scalable deposition. Using blade coated perovskite thin films, we demonstrate perovskite mini-modules with efficiency near 16‥. Using slot-die coating, we show uniform deposition of perovskite thin films on substrate with area larger than 200 cm2. Using slot-diecoated perovskite thin films, we obtain perovskite solar cells with efficiency higher than14‥. Further optimization of coating conditions is expected to improve device performance comparable to those prepared by spin coating for small area devices.

A metal halide perovskite (MHP) solution was developed that is compatible with high speed (1 m min-1) one-step blade coating.MHP solar cells from the developed solution can produce power conversion efficiency over 18% in ambient environment without any addition of antisolvent, gas drying, vacuum treatment or high-temperature annealing. Careful control of the annealing temperature allows fabricating of a more stable MHP due to the increased crystallinity of the MHP film. This development on one-step, antisolvent (or similar processing) treatment free, blade coating technique paves the way for the rollto- roll production of high-efficiency MHP solar cells.

The Solar Energy Research Institute for India and the United States (SERIIUS - http://www.seriius.org) is dedicated to creating a bi-national network of its 40 partners with members from academia, national laboratories, non-profit organizations, and industry to foster new ideas and collaborations to expedite a sustainable solar industry in the US and in India. SERIIUS is developing disruptive technologies through foundational research in sustainable photovoltaics (PV), multi-scale concentrating solar power (CSP) and coupled to an analysis activity to address the critical barriers for solar energy development in India that intersect the grand challenges for solar energy in the U.S. The consortium has published over 330 papers and conference proceedings of which 45 are joint between India and the US. SERIIUS has engaged overs 200 graduate students and had 30 binational intern exchanges.

Perovskite materials use earth-abundant elements, have low formation energies for deposition and are compatible with roll-to-roll and other high-volume manufacturing techniques. These features make perovskite solar cells (PSCs) suitable for terawatt-scale energy production with low production costs and low capital expenditure. Demonstrations of performance comparable to that of other thin-film photovoltaics (PVs) and improvements in laboratory-scale cell stability have recently made scale up of this PV technology an intense area of research focus. Here, we review recent progress and challenges in scaling up PSCs and related efforts to enable the terawatt-scale manufacturing and deployment of this PV technology. We discuss common device and module architectures, scalable deposition methods and progress in the scalable deposition of perovskite and charge-transport layers. We also provide an overview of device and module stability, module-level characterization techniques and techno-economic analyses of perovskite PV modules. Perovskite solar cells (PSCs) have emerged as a revolutionary class of photovoltaic technology. Here, we review recent progress and challenges in scaling up PSCs towards commercialization. We discuss several areas, including device architectures, deposition methods, scalable deposition of perovskite and charge transport layers, device stability, module-level characterization and techno-economic analyses.

Transparent conductive adhesives (TCAs) can enable conductivity between two substrates, which is useful for a wide range of electronic devices. Here, we have developed a TCA composed of a polymer–particle blend with ethylene-vinyl acetate as the transparent adhesive and metal-coated flexible poly(methyl methacrylate) microspheres as the conductive particles that can provide conductivity and adhesion regardless of the surface texture. This TCA layer was designed to be nearly transparent, conductive in only the out-of-plane direction, and of practical adhesive strength to hold the substrates together. The series resistance was measured at 0.3 and 0.8 Ω cm2 for 8 and 0.2% particle coverage, respectively, while remaining over 92% was transparent in both cases. For applications in photovoltaic devices, such as mechanically stacked multijunction III–V/Si cells, a TCA with 1% particle coverage will have less than 0.5% power loss due to the resistance and less than 1% shading loss to the bottom cell.

Excess carrier lifetime plays a crucial role in determining the efficiency of solar cells. In this paper, we use the frequency dependence of inphase and quadrature components of modulated electroluminescence (MEL) to measure the relaxation time (decay) of excess carriers. The advantage of the MEL technique is that the relaxation time is obtained directly from the angular frequency at which the quadrature component peaks. It does not need knowledge of the material parameters like mobility, etc., and can be used for any finished solar cells which have detectable light emission. The experiment is easy to perform with standard electrical equipment. For silicon solar cells, the relaxation time is dominated by recombination and hence, the relaxation time is indeed the excess carrier lifetime. In contrast, for the CIGS solar cells investigated here, the relaxation time is dominated by trapping and emission from shallow minority carrier traps.

For halide perovskite solar cells (PSCs) to fulfill their vast potential for combining low-cost, high efficiency, and high throughput production they must be scaled using a truly transformative method, such as roll-to-roll processing. Bringing this reality closer to fruition, the present work demonstrates flexible perovskite solar cells with 18.1% power conversion efficiency on flexible Willow Glass substrates. We highlight the importance of the transparent conductive oxide (TCO) layers on device performance by studying various TCOs. While tin-doped indium oxide (ITO) and indium zinc oxide (IZO) based PSC devices demonstrate high photovoltaic performances, aluminum-doped zinc oxide (AZO) based devices underperformed in all device parameters. Analysis of X-ray photoemission spectroscopy data shows that the stoichiometry of the perovskite film surface changes dramatically when it is fabricated on AZO, demonstrating the importance of the substrate in perovskite film formation.

The rear side metallization of Si solar cells comes with a number of inherent losses and trade-offs: a larger metallized area fraction improves fill factor at the expense of open-circuit voltage, depositing directly on textured Si leads to low contact resistivity at the expense of short-circuit current, and some metallization processes create defects in Si. To mitigate many of these losses we have developed a novel approach for rear side metallization of Si solar cells, utilizing a transparent conducting adhesive (TCA) to metallize Si without exposing the wafer to the metal deposition process. The TCA consists of an insulating adhesive loaded with conductive microspheres. This approach leads to virtually no loss in implied open-circuit voltage upon metallization. Electrical measurements showed that contact resistivities of 3-9 Ωcm2 were achieved, and an analysis of the transit resistance per microsphere showed that

Methods of making silicon based tandem cells include wafer bonding, depositing absorber layers on the surface, and mechanical stacking. Of these, mechanically stacking after growth retains the individual cell quality during production, but typically requires a four-terminal device. We present a transparent conductive adhesive (TCA) interlayer, designed for transparency in wavelengths that Si absorbs, conductivity for out-of-plane conductivity between cells, and adhesive strength, enabling two-terminal stacked tandems. The developed TCA material is a polymer-particle blend of common transparent adhesives and metal-coated flexible microspheres, capable of bridging micro-scale gaps between uneven/textured surfaces. At 10% microsphere coverage, experimental and theoretical series resistance is compatible with high-efficiency tandem cells on silicon.

Perovskite solar cells have made tremendous progress using laboratory-scale spin-coating methods in the past few years owing to advances in controls of perovskite film deposition. However, devices made via scalable methods are still lagging behind state-of-the-art spin-coated devices because of the complicated nature of perovskite crystallization from a precursor state. Here we demonstrate a chlorine-containing methylammonium lead iodide precursor formulation along with solvent tuning to enable a wide precursor-processing window (up to ∼8 min) and a rapid grain growth rate (as short as ∼1 min). Coupled with antisolvent extraction, this precursor ink delivers high-quality perovskite films with large-scale uniformity. The ink can be used by both spin-coating and blade-coating methods with indistinguishable film morphology and device performance. Using a blade-coated absorber, devices with 0.12-cm2 and 1.2-cm2 areas yield average efficiencies of 18.55% and 17.33%, respectively. We further demonstrate a 12.6-cm2 four-cell module (88% geometric fill factor) with 13.3% stabilized active-area efficiency output. Perovskite-based solar cells are often fabricated by methods that are not industrially scalable. Here, Yang et al. develop an ink formulation which gives similar devices by spin coating, the lab-scale standard, and blade coating, which is a more scalable, industry-relevant deposition method.