Abstract High‐quality charge carrier transport materials are of key importance for stable and efficient perovskite‐based photovoltaics. This work reports on electron‐beam‐evaporated nickel oxide (NiO x ) layers, resulting in power conversion efficiencies (PCEs) up to 18.5% when integrated into solar cells employing inkjet‐printed perovskite absorbers. By adding oxygen as a process gas optimizing the layer thickness, transparent NiO hole layers (HTLs) fabricated, exhibiting an average...

We investigate the electronic states in strained Ga0.62In0.38N0.015As0.985/GaAs multiple- quantum-well structures using photoluminescence and (polarized) excitation measurements at low temperature. From a theoretical fit to experimental data, type-I band alignment for heavy holes with conduction-band offset ratio of about 80% is obtained, while light show an approximately flat alignment. Additionally, our results suggest increased effective electron mass GaInNAs, possibly due interaction...

Multiple-cation mixed-halide (Cs,FA,MA)Pb(I,Br)3 perovskites containing cesium, formamidinium (FA), and methylammonium (MA) possess excellent properties for a wide range of optoelectronic applications such as thin-film photovoltaics or lasers. We investigate the role excitons exciton binding energy EB, relevant effectiveness charge separation in solar cells, well temperature-dependent bandgap Eg which is used an indicator crystal phase transitions. Generalized Elliott fits absorption spectra...

Light-harvesting micro-/nanohierarchical structures replicated from plants' epidermal cells are exploited for photovoltaic applications. Their broadband and omnidirectional antireflection properties, together with their light-trapping capability, analyzed experimentally. Power conversion efficiency gains reported after integrating those replicas onto optimized state-of-the-art organic solar cells. The proposed approach can be applied to different plant species technologies. As a service our...

We observe coherent long-distance propagation of an optical pulse in resonance with the free exciton at high light intensities optically thick semiconductor. The experiments show reshaping, breakup, and a degree transmission. Microscopic calculations using semiconductor Maxwell-Bloch equations yield good agreement experimental data.

We report on order–disorder related band gap changes in Cu2ZnSn(S,Se)4 solar cells which are induced by post-annealing. The of the absorber detected utilizing electroreflectance and analyzed comparison with predictions stochastic Vineyard model. This yields a critical temperature TC=195 °C above layer is entirely disordered within Cu–Zn layers kesterite unit cell. temporal evolution during annealing shows that equilibrium value reached timescale order hours, depending temperature. In...

Cubic InN layers were grown by plasma assisted molecular beam epitaxy on 3C-SiC (001) substrates at growth temperatures from 419to490°C. X-ray diffraction investigations show that the have zinc blende structure with only a small fraction of wurtzite phase inclusions (111) facets cubic layer. The full width half maximum c-InN (002) x-ray rocking curve is less than 50arcmin. lattice constant 5.01±0.01Å. Low temperature photoluminescence measurements yield band gap 0.61eV. At room about 0.56eV...

We investigate the electronic structure of solution-processed perovskite solar cells using temperature-dependent electroabsorption (EA) spectroscopy. Simultaneous measurements absorption and electromodulated spectra semitransparent methylammonium lead iodide facilitate a direct comparison specific features. The EA can be transformed to peak-like line shapes utilizing an approach based on Kramers–Kronig relations. resulting peak positions correspond well discrete excitonic—rather than...

Vacuum-based deposition techniques are a common route for the fabrication of high-quality optoelectronic devices on an industrialized scale at low cost and high yield. In field perovskite-based photovoltaics, however, vacuum methods less researched in community today. Even though fundamental concept thermal evaporation solar cells has been demonstrated, number reports about efficient upscalable all-evaporated approaches employing inexpensive raw materials is still limited. this contribution,...

Decreasing the absorber layer thickness of thin‐film solar cells can be an effective solution for cost reduction photovoltaic electricity generation. Unfortunately, this leads to detrimental effects such as incomplete photon absorption and increased charge carrier recombination at rear electrode. To tackle these losses in ultra‐thin 0.5 µm Cu(In,Ga)Se 2 (CIGS) cells, we developed different passivation structures made MgF Al O 3 molybdenum–CIGS interface, leading localized back contacts. The...

We have studied both theoretically and experimentally the luminescence spectra kinetics of crystalline, disordered solid solutions after pulsed excitation. First, we present model calculations steady-state band shape caused by recombination excitons localized in wells random potential induced disorder. Classification optically active tail states main exciton into two groups is proposed. The majority responsible for optical absorption corresponds to group extended belonging percolation...

The conduction band offset of the type II heterostructure CdS/ZnSe is determined from photoluminescence data single quantum wells. cubic well samples have been grown by compound-source molecular-beam epitaxy. Photoluminescence spectra were measured at low temperatures and evaluated fitting an effective mass model to transition energies. A (0.80±0.1) eV electron for CdS (0.18±0.05)m0 determined.

We report on efficient injection of electron spins into InGaAs-based nanostructures. The spin light-emitting diodes incorporate an InGaAs quantum well or dots, respectively, as a semimagnetic ZnMnSe spin-aligner layer. show circular polarization degree up to 35% for the electroluminescence from wells and 21% dots. can clearly attribute emitted photons alignment in layer by comparison results reference devices (where is replaced ZnSe) all-optical measurements.

Based on solution-processed kesterite-type Cu2ZnSn(S1–x,Sex)4 solar cells, a detailed investigation of the source and effects sodium in absorber will be presented. In contrast to most investigations literature so far, main process for supply during selenization does not seem diffusion out sodium-containing glass substrate but transfer from environment into absorber. Studies influence morphological properties absorbers let us assume that formation big grains is necessarily coupled presence...

Strain-compensated double InGaAs quantum-well saturable Bragg reflectors (SBR's) with high damage thresholds have been developed for use as mode-locking elements in high-average-power neodymium lasers. Nd:YVO4 lasers these new SBR's, which produce transform-limited pulses of 21-ps duration at 90 MHz and an average power 20 W a diffraction-limited output beam. The peak pulse was 10.6 kW. A comparison the operating parameters strained single strain-compensated double-well SBR's indicates that...

Ultrathin, coherently strained CdS layers have been grown epitaxially on ZnS with nominal thicknesses below the critical value for strain relaxation. These CdS/ZnS quantum structures, which show efficient photoluminescence and optical gain in deep blue to ultraviolet spectral range, analyzed respect dimensionality of electronic states. It has found that wide-gap II-VI structures small monolayer fluctuations result such strong localization excitons depth reaches energies around 100 meV....

The influence of the conditions during growth InAs/GaAs quantum-dot structures on GaAs(001) by molecular-beam epitaxy was investigated systematically with respect to achieving photoluminescence in 1 eV range. temperature, As flux, rate, InAs deposit, and interruption time before cap layer were varied. Photoluminescence spectroscopy transmission electron microscopy used study optical structural properties. Large quantum dots range obtained at a low rate 0.0056 ML/s. Analyzing particular...

Multiple-cation mixed-halide perovskites show high power-conversion efficiencies and recently improved stability. But, even most advanced absorber materials still suffer from instabilities of the bandgap under illumination applied bias. Here, we employ modulation spectroscopy as a highly sensitive electro-optical measurement technique to directly reveal such instabilities. We find reversible decrease up 70 meV in complete solar cells. In situ X-ray diffraction measurements bias confirm...

Perovskite absorber layers for thin‐film solar cells can be fabricated by a variety of methods including solution‐ and vacuum‐based methods. Solution‐processed perovskite thin‐films prepared two‐step often suffer from small grains thus reduced optoelectronic performance. In this work, simple universal way to control the crystallization dynamics (CH 3 NH PbI ) thermal evaporation lead iodide subsequent solution‐based conversion in methylammonium solution is presented. By adding concentrations...

In this contribution the authors investigate temperature-dependent conduction band structure of GaAs1−xNx for different nitrogen contents. An analysis their experimental photoreflectance data based on two-band version anticrossing model shows that with decreasing temperature energy effective level EN in GaAsN epilayers shifts significantly to higher energies. Simultaneously, coupling parameter CNM between states and host also rises values.

InAs quantum dot (QD) layers grown by molecular-beam epitaxy were investigated transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. To achieve the highest possible In concentration in QDs, InGaAs (instead of GaAs) cap with different concentrations deposited after growth QD layer. We combine TEM techniques to determine shape, size, composition QDs. By applying a post-processing procedure, we are able reconstruct QDs which is measured too low due embedding material...

We present simulation results for optical modes in micro-pillar cavities that were computed with the finite element method and show good agreement experimental data. By means of this viable tool various influences on quality factor fundamental mode calculated: Firstly, light confinement depends strongly absorption semiconductor cavity material. Here we able to determine absolute maximum factors achievable a GaAs/AlAs Bragg cavity. Furthermore, small pillar diameters as well inclination...

Electromodulated reflectance (ER) is a standard characterization method to determine critical points such as the band gap in structure of semiconductors. These show up spectrally narrow features ER and are typically evaluated using Aspnes's third-derivative functional form. spectra stratified semiconductor systems thin-film solar cells, however, significantly distorted by optical interference due their layered structure. Furthermore, strong built-in electric fields result deviation from...

Biexcitons localized in ultrathin CdS/ZnS single quantum wells with fluctuating well thicknesses are investigated by two-photon absorption and single-exciton spectroscopy. For the binding energy of confined biexciton, a value $\ensuremath{\Delta}{E}_{\mathrm{B}}=38$ meV is determined. Comparing $\ensuremath{\Delta}{E}_{\mathrm{B}}$ CdS bulk exciton ${E}_{\mathrm{Ryd}}=28$ meV, largest known ratio $\ensuremath{\Delta}{E}_{\mathrm{B}}{/E}_{\mathrm{Ryd}}=1.4$ found. Additionally, strong...