We present solution-based fabrication and characterization of the lead-free perovskite-related methylammonium antimony iodide (CH 3 NH 3 ) 3 Sb 2 I 9 compound. By photothermal deflection spectroscopy (PDS), we determined a peak absorption coefficient α ≈ 10 5 cm −1 and an optical band gap of 2.14 eV for amorphous films of (CH 3 NH 3 ) 3 Sb 2 I 9 . Compared to the related Bi compound, the Sb-perovskite shows no exciton peak in its absorption spectrum. The photoluminescence emission (PL) is observed at 1.58 eV, and the Urbach tail energy of this amorphous compound is E u = 62 meV, indicating a substantial amount of energetic disorder. We fabricate a planar heterojunction solar cell with a (CH 3 NH 3 ) 3 Sb 2 I 9 absorber layer that yields a power conversion efficiency of η ≈ 0.5%, already featuring a decent fill factor (FF) of 55% and open-circuit voltage of 890 mV but low photocurrent densities. The result of this basic study on (CH 3 NH 3 ) 3 Sb 2 I 9 shows that this compound is a possible starting point for further research into Sb-based lead-free perovskite solar cells.L ead-based organic−inorganic hybrid semiconductors like CH 3 NH 3 PbI 3 (MAPI) have shown high potential as efficient absorber materials for single-junction solar cells due to their outstanding optoelectronic properties 1 and the easy and cheap fabrication methods. The power conversion efficiencies of these three-dimensional (3D) perovskite solar cells have increased rapidly up to more than 22% in 2016 2−5 after only 6 years of research starting from the first reported perovskite solar cell with an efficiency of 3.8%. 6 However, the low chemical stability of this lead-based perovskite under ambient air and the toxicity of the heavy metal lead could be obstacles for commercialization. 6−11 The tin analogous perovskite compound CH 3 NH 3 SnI 3 has exhibited moderate conversion efficiencies of up to 6% but is even more unstable under air and moisture because of the rapid oxidation of the Sn 2+ state to the Sn 4+ state. 12−14 Another promising group of materials for lead-free alternatives are the zero-dimensional (0D) Biperovskites A 3 Bi 2 X 9 (e.g., A = Cs + , MA + ; X = I − , Br − ). 15−17 These materials show high band gaps of E g > 1.8 eV, 18,19 which are suitable for tandem or triple solar cells. 20,21 Bismuth is a nontoxic element, and the Bi-based perovskites showed a better chemical stability under ambient atmosphere than the MAPI perovskite. 22 However, the Bi-perovskites also show the signature of excitons in their absorption spectrum that have binding energies in the range of 400 meV. 19,22 This leads to relatively low short-circuit current densities due to insufficient exciton splitting and charge carrier extraction. Bi-perovskitebased solar cells exhibit conversion efficiencies of 1% 22 with a TiO x electron transport layer (ETL) and 0.1% 23 in planar devices with pin-architectures where the exciton splitting at the interfaces is even more critical.In this work, we present the exchange of bismuth by antimony, which is less toxic than P...

Careful interpretation of time-resolved photoluminescence (TRPL) measurements can substantially improve our understanding of the complex nature of charge-carrier processes in metal-halide perovskites, including, for instance, charge separation, trapping, and surface and bulk recombination. In this work, we demonstrate that TRPL measurements combined with powerful analytical models and additional supporting experiments can reveal insights into the charge-carrier dynamics that go beyond the determination of minority-charge-carrier lifetimes. While taking into account doping and photon recycling in the absorber layer, we investigate surface and bulk recombination (trap-assisted, radiative, and Auger) by means of the shape of photoluminescence transients. The observed long effective lifetime indicates high material purity and good passivation of perovskite surfaces with exceptionally low surface recombination velocities on the order of about 10 cm=s. Finally, we show how to predict the potential open-circuit voltage for a device with ideal contacts based on the transient and steady-state photoluminescence data from a perovskite absorber film and including the effect of photon recycling.

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The Mott-Schottky analysis in the dark is a frequently used method to determine the doping concentration of semiconductors from capacitance-voltage measurements, even for such complex systems as polymer:fullerene blends used for organic solar cells. While the analysis of capacitance-voltage measurements in the dark is relatively well established, the analysis of data taken under illumination is currently not fully understood. Here, we present experiments and simulations to show which physical mechanisms affect the Mott-Schottky analysis under illumination. We show that the mobility of the blend has a major influence on the shape of the capacitance-voltage curve and can be obtained from data taken under reverse bias. In addition, we show that the apparent shift of the built-in voltage observed previously can be explained by a shift of the onset of space-charge-limited collection with illumination intensity.