Metal halide perovskite solar cells achieve high efficiency and their production of liquid inks requires only a small amount of energy. A team led by Prof. Dr. Eva Unger at the Helmholtz Zentrum Berlin is investigating the production process. At the BESSY II X-ray source, the group analyzed the optimal composition of precursor inks to produce high-quality FAPbI3 Perovskite thin films by aperture coating. Solar cells produced using these inks have been tested under real life conditions in the field for a year and scaled down to a small unit size.
Metal halide perovskites are a particularly promising low-cost class of materials for next-generation solar modules. Perovskite solar cells can be produced by coating processes using liquid inks made from different raw materials and solvents. After coating, the solvents evaporated and the perovskite crystallized to form a more or less homogeneous layer.
Upgradable options
Prof. Dr. Eva Unger’s team at Helmholtz-Zentrum Berlin has extensive experience in solution-based treatment methods and is studying options for scaling up. “Perovskite photovoltaics are the best solution-handled photovoltaic technology, but we are just beginning to understand how the complex interaction of solvent components affects the quality of perovskite layers,” says Eva Unger.
viscosity differences
This is because when halide perovskite layers are coated on large surfaces, unwanted heterogeneities can occur, for example the so-called ribbing structures. “By changing the viscosity of the ink, these effects can be minimized,” says Jinzhao Li, who is doing his PhD with Unger. At BESSY II, he investigated how different solvent combinations affect the crystallization of perovskite films. Best Pin – FAPbI3 In doing so, perovskite solar cells achieve a certified efficiency of 22.3% on a laboratory scale. Jinzhao Li also produced small solar modules (active area of 12.6 cm2) with colleagues from the HySPRINT Innovation Lab and PVcomB, which achieved efficiencies of about 17%.
Outdoor test for a year
Dr. Caroline Ulbrich’s team tested the improved solar cells at PVcomB’s outdoor test facility for an entire year: in the process, the efficiency remained roughly stable in the winter and spring, only dropping in the warmer summer months. “These tests of larger modules under real conditions give us valuable information about the degradation mechanisms in order to further improve the long-term stability of halide perovskite photovoltaics,” says Eva Unger.
