Manipulation of Crystal Orientation and Phase Distribution of Quasi-2D Perovskite through Synergistic Effect of Additive Doping and Spacer Engineering

The diammonium precursor 1,4-phenylenedimethanammonium (PDMA) was used as a large organic spacer for the preparation of Dion-Jacobson-type quasi-2D perovskites (PDMA)(MA)n−1PbnI3n+1 (MA = methylammonium). Films with composition ⟨n⟩ = 5 comprised randomly orientated grains and multiple microstructural domains with locally differing n values. However, by mixing the Dion-Jacobson-type spacer PDMA and the Ruddlesden-Popper-type spacer propylammonium (PA), the crystal orientation in both the vertical and the horizonal directions became regulated. High crystallinity owing to well-matched interlayer distances was observed. Combining this spacer-engineering approach with the addition of methylammonium chloride (MACl) led to full vertical alignment of the crystal orientation. Moreover, the microstructural domains at the substrate interface changed from low-n (n = 1, 2, 3) to high-n (n = 4, 5), which may be beneficial for hole extraction at the interface between perovskite and hole transport layer due to a more finely tuned band alignment. Our work sheds light on manipulating the crystallization behavior of quasi-2D perovskite and further paves the way for highly stable and efficient perovskite devices.</p

Photophysical Study on the Effect of the External Potential on NiO-Based Photocathodes

In the present study, we investigate the effects of the applied external potential on a dye-sensitized NiO photocathode by time-resolved photoluminescence and femtosecond transient absorption spectroscopy under operating conditions. Instead of the anticipated acceleration of photoinduced hole injection from dye into NiO at a more negative applied potential, we observe that both hole injection and charge recombination are slowed down. We cautiously assign this effect to a variation in OH– ion concentration in the inner Helmholtz plane of the electrochemical double layer with applied potential, warranting further investigation for the realization of efficient solar fuel devices

Free-Space Concentration of Diffused Light for Photovoltaics

We are presenting a new strategy to concentrate diffused light in free space based on luminophore doped waveguides with nanophotonic surface control. The efficiency of traditional luminescent solar concentrators (LSCs) has been limited due to loss mechanisms associated with every single component of the process, such as the luminophore quantum yield, reabsorption/emission rates, waveguide parasitic absorption, and unwanted escape. Here, we are proposing a paradigm shift to mitigate this issue: Instead of trapping light in waveguides, waveguides are designed to allow for escape under a specific escape cone

Free-space luminescent solar concentrators: Analytical performance model and experiments

We present free-space luminescent solar concentrators (LSCs), analytical performance calculations, and experiments. This will enable concentrating diffused light onto commercial solar modules mitigating performance challenges of conventional LSCs

Analytical Model for the Performance of a Free-Space Luminescent Solar Concentrator

Conventional luminescent solar concentrators suffer from high losses due to the large path length inside the device. Our system reduces these losses by using the free-space to collimate the light. We have developed an analytical model for the performance of those free-space luminescent solar concentrators. Our model takes all loss mechanisms into account and outputs the angle and wavelength dependent emission. Using realistic material parameters, we calculate the intensity emitted by the free space concentrator to be 1.5 times higher than that of a perfect diffuse reflector for all emission angles below 19 degrees

Photophysical Study on the Effect of the External Potential on NiO-Based Photocathodes

In present study we investigate the effect of the external potential on a dye-sensitized NiO photocathode on the light-induced charge carrier dynamics by time-resolved photoluminescence and femtosecond transient absorption spectroscopy under operating conditions. Instead of the anticipated acceleration of photoinduced hole injection from dye into NiO at more negative applied potential, we observe that both hole injection and charge recombination are slowed down. We assign this effect to a variation in OH- ion concentration in the inner Helmholtz plane (IHP) of the electrochemical double layer with applied potential, showing that ion adsorption and desorption onto the NiO surface play an essential role as a relay in light-induced charge transfer and recombination. Our work highlights the key role of ions at the electrode surface and in the electrolyte in the realization of efficient solar to fuel devices