Wide-bandgap hybrid organic-inorganic perovskite solar cells (PSCs) are of interest to the research community because of their potential for high performance, low-cost and lightweight integration as persistent photovoltaic (PV) sources for tandem PV, space, expeditionary, and underwater power generation. However, despite recent advancements in hybrid PSCs with bandgaps close to 1.75 eV, there are fewer research efforts exploring single-junction PSCs with band gaps 1.8 - 2.1 eV. Here, we show the solution-processed fabrication of a wide-bandgap hybrid PSCs utilizing a formamidinium-based mixed iodide/bromide perovskite composition (band gap ~1.84 eV) as the active layer. Additionally, we employ solution-processable electron and hole transport materials, SnO 2 , and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA). Our work illustrates the pivotal role that interfaces between the transport materials and the perovskite layer play on the open circuit voltage $(Voc)$ of these devices. For example, we observe an increase in the $Voc$ of devices when we add a C 60 -SAM $(4-(1^{\prime}, 5^{\prime}$ -dihydro-1’ -methyl-2’ $H-[5,6]\text{fullereno}-\mathrm{C}_{60}-\mathrm{I}_{h}-[1,9-c]\text{pyrrol}-2^{\prime}-\text{yl})\text{benzoic}$ acid) interlayer between the SnO 2 and perovskite layer, as well as utilizing effective p-type doping of the hole transport layer. We hypothesize that these results are due to an improved energetic band alignment and/or improved charge extraction efficiencies at those interfaces. Through careful manipulation of perovskite/transport material interfaces, we can achieve wide-bandgap hybrid PSCs with a $Voc$ greater than 1.1 V. This study is one of only a few detailed works into single-junction PSCs with a bandgap $> 1.75\text{eV}$ utilizing a hybrid formamidinium-based perovskite composition.

A method is proposed for large area, highly uniform photoluminescence imaging of single and multi-junction solar cells and solar cell arrays. Relative photoluminescence across a large area can be rapidly determined due to highly uniform excitation illumination and minimal measurement artifacts. Varying the wavelength of the excitation illumination enables the measurement of the photoluminescence of a variety of solar cell materials and of multiple sub-cells in a multi-junction device. This method allows for rapid characterization of spatially resolved device parameters. Thereby providing insight to the condition of solar cells including the nature of potential degradation that would not be readily conveyed via overall performance measurements using techniques that can be performed while the array is installed into a functional end use system.

There is a need for characterization of multi-junction solar cell based test coupons under collimated sunlight for both terrestrial and space applications. These applications include solar cell angle measurements and concentrator systems. The U.S. Naval Research Laboratory (NRL) has modified a 3-zone Spectrolab LAPSS (Large Area Pulsed Solar Simulator) to provide a tunable spectrum with a 1° collimation for testing of solar arrays. NRL has added filters and a complete measuring system capable of testing individual cells and small concentrator coupons requiring collimation comparable to the sun.

We report a space tandem solar cell enabling an enhanced power conversion efficiency with radiation tolerance in low radiation environments for space photovoltaic (PV) applications. The presented space perovskite/Si 4-terminal tandem cell features an efficient semitransparent perovskite top cell with the bandgap of 1.61 eV on a thin Si space solar cell specifically designed for high radiation tolerance in space. Under a simulated air mass zero (AM0) spectrum (136.6 mW/cm2), the space tandem solar cell by combining the perovskite solar cell with a thin Si space solar cell results in a power conversion efficiency of 21.1% surpasses a limited efficiency of ~17% in a single junction Si space solar cell. Considering the potential for developing more efficient, low-cost perovskite PV technology, our approach of using the thin Si space solar for the space tandem cells makes it possible to realize cost-effective PV power generation in space.

We focus on utilizing sputtered indium tin oxide (ITO) as a recombination layer, having low junction damage to an n-type silicon solar cell with a front-side tunnel oxide passivating electron contact, thereby enabling the development of a high efficiency monolithic perovskite/Si tandem device. High transparency and low resistivity ITO films are deposited via low power DC magnetron sputtering at room temperature onto a front-side thin SiOx/n(+) poly-Si contact in a complete Cz n-Si cell with a back-side Al2O3/SiNx passivating boron-diffused p(+)-emitter on a random pyramid textured surface. We report the cell characteristics before and after ITO sputtering, and we find a cure at 250 degrees C in air is highly effective at mitigating any sputtering induced damage. Our ITO coated sample resulted in an implied open-circuit voltage (iV(oc)) of 684.7 +/- 11.3 mV with the total saturation current density of 49.2 +/- 14.8 fA/cm(2), an implied fill factor (iFF) of 81.9 +/- 0.8%, and a contact resistivity in the range of 60 m Omega-cm(2) to 90 m Omega-cm(2). After formation of a local Ag contact to the rear emitter and sputtered ITO film as the front-side contact without grid fingers, the pseudo-efficiency of 20.2 +/- 0.5% was obtained with the V-oc of 670.4 +/- 7 mV and pseudo FF of 77.3 +/- 1.3% under simulated one sun with the calculated short-circuit current density of 30.9 mA/cm(2) from the measured external quantum efficiency. Our modelling result shows that efficiency exceeding 25% under one sun is practically achievable in perovskite/Si tandem configuration using the ITO recombination layer connecting a perovskite top cell and a poly-Si bottom cell.

Metal halide perovskite solar cells have progressed rapidly over the past decade, providing an exceptional opportunity for space photovoltaic (PV) power applications. However, the solar cells to be used for space power have to demonstrate a stable operation under extreme conditions, particularly concerning harsh radiations. In contrast to previously reported superior stability of low PV performance perovskite solar cells against high-energy radiation, we investigate the effects of high-energy electron beam irradiation on the degradation of perovskite solar cells with a high-power conversion efficiency exceeding 20%. We find very high remaining factors of >87.7% in the open-circuit voltage (VOC) and >93.5% in the fill factor (FF) and a significantly decreased short-circuit current density (JSC) after the exposure to high-fluence electron irradiations of 1015 e/cm2. The pronounced loss of JSC is due to the decreasing transmittance of the soda-lime glass substrate and the partial decomposition of the perovskite absorber layers. The irradiated cells retained superior remaining factors in both VOC and FF, demonstrating a superior tolerance of perovskite solar cells after the exposure to the electron irradiation. These results show that perovskite solar cells hold great potential for space PV power applications if stable perovskite compositions and space-suitable substrates are employed.

The Naval Research Laboratory has developed a low-power, real-time displacement damage dosimeter (RT3D). RT3D consists of two components; one being the measurement electronics and the second being the actual dosimeter (GaAs diode) exposed to the radiation source. RT3D accumulates displacement damage passively (without power) and the displacement damage dose (DDD) is measured at will with measurement electronics by measuring the GaAs diode dark current at one or more forward bias voltages. The DDD is subsequently determined in real-time from a calibration curve derived from ground-based testing. The dosimeter is capable of measuring approximately three orders of magnitude in DDD. The dosage measurement range of the sensor can be modified by placing an absorber material over the sensor. Proton testing performed in situ yielded an error estimate determination to within 10% for simulated space use.

In this study, we investigate the impact of the deposition of indium tin oxide (ITO) via DC magnetron sputtering on tunnel oxide passivating poly-Si contacts. Before ITO deposition to the tunnel SiO x passivating n + poly-Si rear-contact on the cell structure with an SiN x /Al2O 3 passivating boron emitter, the implied open-circuit voltage (iV oc ) and implied fill factor (iFF) were measured to be 694±10 mV and 83±0.6%, respectively. After ITO sputtering and curing annealing, the iV oc and iFF were almost fully recovered, resulting in the iVoc of 685±11 mV and iFF of 81.9±0.8%. The characteristic of fully recovered effective lifetime is attributed to unique sputtering conditions employing a very low power density at room temperature and curing.

Flight endurance and power are limiting factors affecting UAV applications today due to battery weight and capacity. Solar arrays integrated into the wing surface can provide additional power dependent on the sun, weight, wing area, and efficiency, and have demonstrated more than doubled flight times. With most wing surfaces having some degree of curvature and flexure during flight, stresses can be induced on the solar arrays. Photoluminescence is used to assess wing stresses by optically identifying crack propagation in the cells. NRL has built a variety of wings for UAVs from solar cell technologies. This paper intends to provide a demonstration of using this technique to study solar cell cracking through the array assembly process from wing integration to flight.

In this paper, we report findings from a micro CPV module, employing 170 μm GaAs-based 2J CPV cells, assembled on glass substrates using micro-transfer printing. The CPV array uses all-glass lens arrays to focus the light with a geometric concentration ratio of 740 suns, and a bifacial, monocrystalline silicon solar cell behind the substrate to capture the diffuse component of the light. We found that the diffuse capture creates a significant performance boost over CPV alone, and study the role of bifacial capture on the overall performance. The highest combined efficiency with respect to global normal irradiance was 25.4% for the module, measured by outdoor testing in Washington, DC.

Modern silicon photovoltaic (PV) cells have high external quantum efficiencies (>70%) from 900nm-1070nm, and are ideally suited as laser power receivers to match the wavelength of high power lasers available today. Silicon PV cells are ~300X less expensive than TTT-V photovoltaic cells making them economical alternatives for large area receivers. A large receiver benefits the laser side of a wireless power system by reducing the requirement for maintaining a small beam at a great distance and eases the wireless receiver design by allowing waste heat to be spread over a larger surface area. Finally, a silicon PV array can efficiently combine solar energy harvesting during the day, and laser energy power transfer at night with a single low-cost array. In this paper we study commercially available silicon solar cells, evaluate their suitability for a laser power converter, and discuss some of the system related aspects of fielding a laser power converter.

Unmanned Aerial Vehicles (UAVs) are expanding in both military and commercial markets. Most UAVs are limited in flight duration and due in part to the weight of energy storage. Solar cells integrated into the wing surface can provide additional power dependent on the sun, weight, wing area, and efficiency. NRL has built a variety of wings for UAVs from solar cell technologies which include Si, thin flexible GaAs, triple junction InGaP/GaAs/Ge, and Inverted Metamorphic Multi-Junction (IMM) for comparison. NRL has flown these solar technologies demonstrating flights in excess of 10 hrs with only 4 hrs of onboard energy storage. This paper intends to provide a side-by-side comparison of these technologies for design and cost considerations on mission feasibility.

Foldable PV modules based upon different PV technologies were evaluated in the Naval Research Laboratory (NRL) for mobile solar power generation. We performed outdoor PV performance comparison of foldable and flexible modules that were mounted on the NRL rooftop for 75 days. We show that foldable PV modules based on CIGS and crystalline Si cells have good stability without performance losses. Other prototype PV modules consisting of amorphous Si, III-V based multijunction solar cells show a significant decrease in power at maximum power point (P mpp ) with losses of more than 10% due to non-optimized module encapsulation materials and processing. For the selected modules, reliability and durability testing results including damp heat test will be discussed.

We examine thermally evaporated MoOx films as a full-area rear contact to crystalline p-type Si solar cells for efficient hole-selective contacts. Prior to front- and rear-metallization, the implied open-circuit voltage (iVoc) is evaluated to be 646 mV with implied fill factor (iFF) of 82.5% for the tunnel SiOx/MoOx rear contacted cell structure with the passivated emitter on the textured surface, showing it is possible to achieve an implied 1-sun efficiency of 20.8%. Numerical simulation reveals that the electron affinity (χ) of the MoOx material strongly influences the performance of the MoOx contacted p-Si cell. Simulated band diagrams show that the values in χ of the MoOx layer must be sufficiently high in order to lower junction recombination, indicating that the highest efficiency of 21.1% is achievable for a high χ of 5.6 eV of MoOx films and back surface recombination velocity of <100 cm/s at p-Si/MoOx.

In this work, we demonstrated an enhanced surface passivation of epitaxially grown boron-doped Si emitters by replacing thermal SiO2 as a passivation layer employed in a 15.9% efficient 21-mu m Si solar cell (88 cm(2)) on stainless steel with a remote-plasma atomic layer deposition (ALD) of an Al2O3 film. A thin Al2O3 film deposited by remote-plasma ALD was very effective at reducing the emitter saturation current density (J(0e)) of epitaxial p(+)-emitter to 16.2 fA/cm(2), compared to the J0e of 184.9 fA/cm(2) by thermal SiO2 films. This reduction in J(0e) enables an increase in an implied open-circuit voltage (iVoc) from 630 to 688mV. Quokka simulation shows that about a 1.1% absolute efficiency increase in the calculated baseline efficiency of a 15.1% of the ultrathin Si solar cell can be achievable by enhancing emitter surface passivation without changing the concentration in either the epi-emitter or epi-base. Finally, our results show that a high efficiency of 17.3% can be reached from the calculated baseline efficiency of 15.1% using the optimized conditions of an epitaxially grown emitter in combination with increasing the base doping concentration and improved base recombination lifetime. (C) 2017 The Japan Society of Applied Physics

In this work, a multijunction solar cell is developed on a GaSb substrate that can efficiently convert the long‐wavelength photons typically lost in a multijunction solar cell into electricity. A combination of modeling and experimental device development is used to optimize the performance of a dual junction GaSb/InGaAsSb concentrator solar cell. Using transfer printing, a commercially available GaAs‐based triple junction cell is stacked mechanically with the GaSb‐based materials to create a four‐terminal, five junction cell with a spectral response range covering the region containing >99% of the available direct‐beam power from the Sun reaching the surface of the Earth. The cell is assembled in a mini‐module with a geometric concentration ratio of 744 suns on a two‐axis tracking system and demonstrated a combined module efficiency of 41.2%, measured outdoors in Durham, NC. Taking into account the measured transmission of the optics gives an implied cell efficiency of 44.5%.

We examine the potential to enhance cell performance using wide bandgap metal oxide films as full-area rear contacts to p-type crystalline Si (c-Si) solar cells. We aim to introduce a band offset through wide bandgap nickel oxide rather than introducing a band bending through transition metal oxides (e.g. MoO x , V 2 Ox, WO x ). Our numerical simulation shows it is possible to achieve one-sun efficiency of 21.6% with the open-circuit voltage (V oc ) of 652 mV, the short-circuit current density (J sc ) of 39.9 mA/cm2 and the fill factor (FF) of 82.5% when the back surface recombination velocities is 100 cm/s at p-Si/NiO x .

Unmanned Aerial Vehicles (UAVs) are rapidly growing in both military and commercial markets. One shortfall of UAVs is the amount of time they can fly, being limited by the energy storage. Solar cells can be integrated into the wing surface to provide additional power, dependent on the sun, weight, wing area, and efficiency. NRL is building a UAV with wings from a variety of solar cell technologies, which includes high efficiency Si, thin flexible GaAs, triple junction InGaP/GaAs/Ge, and Inverted Metamorphic Multi-Junction (IMM) for direct comparison and to improve flight endurance. The UAV also incorporates the necessary power management system required to maximize the solar power available. In addition to solar cells, this plane can also utilize thermal updrafts to soar. Flight data is provided which includes all electrical parameters for comparison studies.