Adding cesium (Cs) and rubidium (Rb) cations to FA0.83MA0.17Pb(I0.83Br0.17)3 hybrid lead halide perovskites results in a remarkable improvement in solar cell performance, but the origin of the enhancement has not been fully understood yet. In this work, Time-of-Flight (ToF), Time-Resolved Microwave Conductivity (TRMC), and Thermally Stimulated Current (TSC) measurements were performed to elucidate the impact of the inorganic cation additives on the trap landscape and charge transport properties within perovskite solar cells. These complementary techniques allow for the assessment of both local features within the perovskite crystals and macroscopic properties of films and full devices. Strikingly, Cs-incorporation was shown to reduce the trap density and charge recombination rates in the perovskite layer. This is consistent with the significant improvements in the open-circuit voltage and fill factor of Cscontaining devices. By comparison, Rb-addition results in an increased charge carrier mobility, which is accompanied by a minor increase in device efficiency and reduced current-voltage hysteresis. By mixing Cs and Rb in quadruple cation (Cs-Rb-FA-MA) perovskites, the advantages of both inorganic cations can be combined. Our study provides valuable insights into the role of these additives in multiple-cation perovskite solar cells, which are essential for the design of highperformance devices.

Window integrated photovoltaics for automotive and building applications are a promising market segment for organic solar modules. Besides semi‐transparency, window integrated applications require a reasonable transparency perception and good color rendering properties in order to be suitable for realistic scene illumination. Here, the transmitted light through semi‐transparent organic solar cells comprising the polymer/fullerene blend poly[(4,4'‐bis(2‐ethylhexyl)dithieno[3,2‐b:2',3'‐d]silole)‐2,6‐diyl‐alt‐(2,1,3‐benzothiadiazole)‐4,7‐diyl]: [6,6]‐phenyl C71‐butric acid methyl ester (PSBTBT:PC70BM) as active layer and a sputtered aluminum doped zinc oxide cathode were found to exhibit a color neutral perception for the human eye and very good color rendering properties. Moreover, the electrical cell properties allow for efficient energy harvesting with an overall power conversion efficiency η ≈ 3%.

Based on the well-known beneficial effect of a thin LiF layer underneath Al contacts for organic solar cells, a comparative study of interlayers made from the alkaline fluorides LiF, NaF, and KF is presented for polymer bulk heterojunction solar cells. The overall suitability of these materials and the underlying mechanisms are discussed. While an improvement in cell efficiency up to a factor of 2 can be reached with all three fluorides, the necessary thickness of the interlayer for maximum improvement is smallest for NaF and largest for LiF, suggesting the alternative use of NaF instead of LiF.

provide good solubility in organic solvents and processability, we attached branched alkyl substituents at the DTP-nitrogen (ethylhexyl (EH) 1 , 4 , octylnonyl (ON) 2 , 5 , hexyldecyl (HD) 3 , 6 ) and hexyl side chains to each thiophene unit in a regioregular fashion as a mimic of the well-known and frequently used regioregular poly(3-hexylthiophene). [ 26 ] Thereby, the hexyl chains were attached either at the outer ( 1 -3 ) or inner ( 4 -6 ) positions thus yielding three isomeric pairs, which only differ in the positioning of the side chains. As a result, excellent solubilities of ≥120 mg mL −1 in chloroform for molecules 5 and 6 have been obtained. First solar cell results of oligomer pair 1 and 4 have recently been published and we discovered a striking difference between the photovoltaic behavior of the two isomers. [ 16 ] Whereas the so far highest PCE of 4.8% for any DTP-based oligomer has been obtained for oligothiophene 1 and PC 61 BM in BHJSCs, isomer 4 showed a lower performance (0.8%), which we attributed to the different blend morphologies and phase separation probed by atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. [ 16 ] The detailed photovoltaic behavior, further optimization, and characterization of the photoactive layers of the whole series of soluble DTP-oligothiophenes 1 -6 is now described. Signifi cant improvement of the oligomer BHJSC performance was obtained by SVA, which was investigated by absorption spectroscopy, grazing incidence XRD (GI-XRD), and AFM. After extensive optimization, power conversion effi ciencies up to 6.1% and fi ll factors greater than 70% were achieved.

Improved phase purity in 2D hybrid perovskite thin films with horizontal crystal orientation was achieved through slow crystallization employing lead-complexing solvent additives.