Rubidium antimony halides are a promising low toxic alternative to organo-lead halide perovskites as photovoltaic material. In this contribution, we systematically investigate the influence of varying the bromide to iodide ratio on the structural, optical, and photovoltaic properties of Rb3Sb2­Br9–x I x (x = 0–9). Single crystal data reveal that all compounds crystallize in a 2D-layered monoclinic crystal structure. Sequential substitution of iodide with the smaller bromide does not change the crystal system; however, increasing the bromide content results in a shrinkage of the unit cell as well as in a blue shift of the absorption onset, increasing the band gap from 2.02 to 2.46 eV. Whereas the photovoltaic properties of bromide rich compounds are limited due to a preferential orientation of the layered structure parallel to the substrate, which is detrimental to charge transport, solar cells with Rb3Sb2I9 as absorber material display power conversion efficiencies of 1.37%. Moreover, the devices exhibit low hysteresis properties and are stable for more than 150 days stored under inert atmosphere.

A perylene-based acceptor (PMI-FF-PMI), consisting of two perylene monoimide (PMI) units bridged with a dihydroindeno[1,2 b]fluorene molecule was developed as a potential non-fullerene acceptor (NFA) for organic solar cells (OSCs)....

Perovskite solar cells with a planar p-i-n device structure offer easy processability at low temperatures, suitable for roll-to-roll fabrication on flexible substrates. Herein we investigate different hole transport layers (solution processed NiO x , sputtered NiO x , PEDOT:PSS) in planar p-i-n perovskite solar cells using the triple cation lead halide perovskite Cs 0.08 (MA 0.17 FA 0.83 ) 0.92 Pb(I 0.83 Br 0.17 ) 3 as absorber layer. Overall, reproducible solar cell performances with power conversion efficiencies up to 12.8% were obtained using solution processed NiO x as hole transport layer in the devices. Compared to that, devices with PEDOT:PSS as hole transport layer yield efficiencies of approx. 8.4%. Further improvement of the fill factor was achieved by the use of an additional zinc oxide nanoparticle layer between the PC 60 BM film and the Ag electrode.

Solar cells based on the novel triple cation tin perovskite MA0.75FA0.15PEA0.1SnI3 exhibit PCEs of 5.0% and notably good stability over more than 5000 hours.

Lead halide perovskites have proved to be exceptionally efficient absorber materials for photovoltaics. Besides improving the properties of the perovskite absorbers, device engineering and the optimization of interfaces will be equally important to further the advancement of this emerging solar cell technology. Herein, we report a successful modification of the interface between the NiO x hole transport layer and the perovskite absorber layer using 4-bromobenzylphosphonic acid based selfassembled monolayers leading to an improved photovoltaic performance. The modification of the NiO x layer is carried out by dip coating which allows sufficient time for the self-assembly. The change in the surface free energy and the non-polar nature of the resulting surface is corroborated by contact angle measurements. X-ray photoelectron spectroscopy confirms the presence of phosphor and bromine on the NiO x surface. Furthermore, the resultant solar cells reveal increased photovoltage. For typical devices without and with modification, the photovoltage improves from 0.978 V to 1.029 V. The champion V OC observed was 1.099 V. The increment in photovoltage leads to improved power conversion efficiencies for the modified cells. The maximum power point tracking measurements of the devices show stable power output of the solar cells.

Perylene monoimide based non-fullerene acceptors with fluorene, silafluorene and carbazole as linkers were synthesized and compared regarding their structural, optical, electronic and photovoltaic properties.

In this work, the influence of a partial introduction of bromide (x = 0-0.33) into MA 0.75 FA 0.15 PEA 0.1 Sn(Br x I 1−x) 3 (MA: methylammonium, FA: formamidinium, PEA: phenylethylammonium) triple cation tin perovskite on the material properties and photovoltaic performance is investigated and characterized. The introduction of bromide shifts the optical band gap of the perovskite films from 1.29 eV for the iodide-based perovskite to 1.50 eV for the perovskite with a bromide content of x = 0.33. X-ray diffraction measurements reveal that the size of the unit cell is also gradually reduced based on the incorporation of bromide. Regarding the photovoltaic performance of the perovskite films, it is shown that already small amounts of bromide (x = 0.08) in the perovskite system increase the open circuit voltage, short circuit current density and fill factor. The maximum power conversion efficiency of 4.63% was obtained with a bromide content of x = 0.25, which can be ascribed to the formation of homogeneous thin films in combination with higher values of the open circuit voltage. Upon introduction of a higher amount of bromide (x = 0.33), the perovskite absorber layers form pinholes, thus reducing the overall device performance.