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Lanthanide-based upconversion (UC) allows harvesting sub-bandgap near-infrared photons in photovoltaics. In this work, we investigate UC in perovskite solar cells by implementing UC single crystal BaF2:Yb3+, Er3+ at the rear of the solar cell. Upon illumination with high-intensity sub-bandgap photons at 980 nm, the BaF2:Yb3+, Er3+ crystal emits upconverted photons in the spectral range between 520 and 700 nm. When tested under terrestrial sunlight representing one sun above the perovskite's bandgap and sub-bandgap illumination at 980 nm, upconverted photons contribute a 0.38 mA/cm2 enhancement in the short-circuit current density at lower intensity. The current enhancement scales non-linearly with the incident intensity of sub-bandgap illumination, and at higher intensity, 2.09 mA/cm2 enhancement in current was observed. Hence, our study shows that using a fluoride single crystal like BaF2:Yb3+, Er3+ for UC is a suitable method to extend the response of perovskite solar cells to near-infrared illumination at 980 nm with a subsequent enhancement in current for very high incident intensity.

Despite promising power conversion efficiencies, a key barrier for the future commercialization of perovskite-based solar cells (PSCs) is their lack of stability when exposed to sunlight for extend...

Hybrid organic–inorganic perovskites are highly promising candidates for the upcoming generation of single- and multijunction solar cells. Despite their extraordinarily good semiconducting properti...

Achieving efficient devices while maintaining a high fabrication yield is a key challenge in the fabrication of solution-processed, perovskite-based light-emitting diodes (PeLEDs). In this respect, pinholes in the solution-processed perovskite layers are a major obstacle. These are usually mitigated using organic electron-conducting planarization layers. However, these organic interlayers are unstable under applied bias in air and suffer from limited charge carrier mobility. In this work, we present a high brightness p-i-n PeLED based on a novel blade-coated silver microflake (SMF) rear electrode, which allows for a low-cost nanocrystalline ZnO inorganic electron-transporting layer to be used. This novel SMF contact is crucial for achieving high performance as it prevents the electrical shorting suffered when standard thermally evaporated silver rear contacts are used. The fabricated PeLEDs exhibit an excellent maximum luminance of 98,000 cd/m2, a maximum current efficiency of 22.3 cd/A, and a high external quantum efficiency of 4.6% under 5.9 V forward bias. The SMF rear contact can be printed and scaled at low cost to large areas and applied to flexible devices.

Hybrid lead halide perovskite solar cells (PSCs) in tandem application with copper indium gallium diselenide (CIGS) solar cells represent one of the most promising all-thin-film technologies for ne...

Advanced optical concepts, making use of tailored microstructured front cover glasses, promise to reduce the losses encountered with encapsulated solar modules. However, implementing optical concepts into the conventional architecture of encapsulated solar modules and simultaneously maintaining high durability represent a severe technological challenge. The liquid glass technique offers a route to meet this challenge by enabling the implementation of these optical concepts directly into the durable front cover glass of solar modules. In this work, we demonstrate for the first time two showcases of texturing fused silica front cover glass, using the facile liquid glass technique: (I) multifunctional microcone textures that reduce front-side reflection losses by ∼80% compared to a planar reference, which correlates to an increase in short-circuit current density of encapsulated planar monocrystalline silicon heterojunction solar cells by 2.9 mA cm-2, and exhibit strong hydrophilic behavior facilitating self-cleaning and (II) embedded freeform surface cloaks that redirect incident light away from the metallic contact grids of the solar cell and demonstrate a cloaking efficiency of ∼88%.

Recently, continuous-wave (CW) lasing was demonstrated at room temperature in quasi-2D perovskites. For 3D films, CW lasing at room temperature remains challenging. Issues hampering 3D materials include the temperature dependence of the (a) distribution of carrier energies, (b) buildup of photoinduced nonradiative channels, and (c) rates of bimolecular versus Auger recombination. We study the latter in a phase-stable 3D perovskite using high-index substrates to completely suppress amplified spontaneous emission (ASE). The bimolecular recombination coefficient decreases from 80 to 290 K (from (6.4 to 1.1) × 10

In this work we report on the coloring of perovskite solar cells (PSC) by combining the ease of freedom in design of the solar cell’s shape with the bright color of luminescent down-shifting (LDS) layers. Both the perovskite solar cell and the LDS layers are fabricated with digital inkjet-printing processes, such that the perceived color of the devices can be tuned independently from the shape of the device. The results demonstrate that a strong color perception of the PSCs with the use of luminescent materials of various colors can be achieved at a relatively small (∼17%) reduction of power conversion efficiency.

Most high-efficiency perovskite solar cells (PSCs) rely on titanium dioxide (TiO 2 ) electron transport layers (ETLs) that are usually processed at high temperature (>450 °C). Consequently, a fully solution-based process of PSCs with TiO 2 ETL on inexpensive flexible polymer substrates is not feasible. Therefore, a scalable low-temperature TiO 2 ETL is developed based on presynthesized crystalline nanoparticle TiO 2 (np-TiO 2 ). The presented synthesis process offers control over the doping, the hydrodynamic diameter, and the solvent of the np-TiO 2 . High initial power conversion efficiency (PCE) of 19.5% (stabilized at 18.2%) of PSC processed on the np-TiO 2 ETL is demonstrated with spin-coated methylammonium lead iodide (CH 3 NH 3 PbI 3 ). Furthermore, it is shown that other perovskite absorber layers that include evaporated CH 3 NH 3 PbI 3 and triple cation perovskite, Cs 0.1 (MA 0.17 FA 0.83 ) 0.9 Pb(I 0.83 Br 0.17 ) 3 , also show very high initial PCE, 14.5% and 19%, respectively. The possibility of doping the np-TiO 2 with niobium (Nb 5+ ) also reduces the resistance of the np-TiO 2 ETL, allowing for thick ETLs that are beneficial for rough substrates. Facile upscaling of the deposition of the np-TiO 2 ETL by inkjet printing, blade coating, and slot-die coating is also demonstrated, having high uniformity, resulting in prototype PSCs with a stable PCE > 15%.

Noncontact inkjet printing offers rapid and digital deposition combined with excellent control over the layer formation for printed perovskite solar cells. In this work, inkjet printing is used to deposit triple cation perovskite layers with 10% cesium in a mixed formamidinium/methylammonium lead iodide/bromide composite for solar cells with high temperature and moisture stability. A reliable process control over a wide range of perovskite layer thickness from 175 to 780 nm and corresponding grain sizes is achieved by adjusting the drop spacing of the inkjet printer cartridge. A continuous power output at constant voltage, resulting in a power conversion efficiency of 12.9%, is demonstrated, representing a major improvement from previously reported inkjet-printed methylammonium lead triiodide perovskite solar cells. Moreover, this work highlights the extended resistance of triple cation perovskite solar cells against heat and moisture for our ambient inkjet printing approach. The presented results are a p...

Nature’s evolution provides a multitude of answers to scientific and key technological challenges such as the light harvesting. In this work, we investigate the optical properties of the unique texture of viola petals for the purpose of improved light harvesting in photovoltaics. We find that crystalline silicon solar cells encapsulated with a transparent coating show a 6% improvement in power conversion efficiency if the viola petal texture is replicated onto the front surface. This gain is based on a broadband enhancement in current generation that originates from the exceptional optical properties of the viola surface texture, combining micro- and nanotexture. The microcones of this hierarchical texture demonstrate strong and broadband light incoupling effects as well as retro-reflection capabilities, and the nanowrinkles further decrease the reflection losses. Using rigorous optical simulation, we analyze and explain the working principle ruling the light harvesting properties of this dual-scale texture.

Space charge limited photocurrent is typically described as the limiting factor in carrier extraction efficiency for organic bulk heterojunctions with increasing thickness. It successfully characterizes the carrier extraction efficiency in these devices with thin to moderate thickness and dissimilar carrier mobilities. However, in this article we show that space charge limited photocurrent cannot solely explain the intensity dependent spectral response of extremely thick organic photovoltaics. In addition, interfacial depletion regions near the contacts contribute to the field distribution and carrier collection. Here, we describe charge collection efficiency with an optical p-i-n model, allowing for collection from band bending due to mobility-induced and interfacial-doping-induced space charge regions. We verify the model with up to 1400 nm thick spray-coated devices in both p-i-n (conventional) and n-i-p (inverted) architecture, including variations of thickness, illumination intensity, transport materials, and bifacial (semitransparent) devices.