Replacing toxic solvents with nonhazardous solvents is one of the key challenges for industrial scale commercialization of thin film perovskite photovoltaics. Here, nonhazardous solvent/alcohol/acid systems are presented for the single‐step deposition of pinhole‐free perovskite layers with combined lead halide precursors of Pb(CH3CO2)2·3H2O, PbCl2, and CH3NH3I. Comparable performance to standard hazardous inks is achieved: devices with 15.1% power conversion efficiency are demonstrated and maintain 13.5% tracked for 5 min at maximum power point. Blade coated 4 cm2 solar modules fabricated with highest performing device ink attain 11.9% in power conversion efficiency.

We report on a perovskite solar module with an aperture area of 4 cm 2 and geometrical fill factor of 91%. The module exhibits an aperture area power conversion efficiency (PCE) of 13.6% from a current-voltage scan and 12.6% after 5 min of maximum power point tracking. High PCE originates in pinhole free perovskite films made with a precursor combination of Pb(CH 3 CO 2 ) 2 ·3H 2 O, PbCl 2 , and CH 3 NH 3 I. Broader contextRecently, significant progress has been made in organometallic halide perovskite solar cell research, boosting the record certified power conversion efficiency (PCE) up to 20.1%.

Perovskites with bandgaps between 1.7 and 1.8 eV are optimal for tandem configurations with crystalline silicon (c-Si) because they facilitate efficient harvest of solar energy. In that respect, achieving a high open-circuit voltage (V OC ) in such wide-bandgap perovskite solar cells is crucial for a high overall power conversion efficiency (PCE). Here, we provide key insights into the factors affecting the V OC in wide-bandgap perovskite solar cells. We show that the influence of the hole transport layer (HTL) on V OC is not simply through its ionization potential but mainly through the quality of the perovskite−HTL interface. With effective interface passivation, we demonstrate perovskite solar cells with a bandgap of 1.72 eV that exhibit a V OC of 1.22 V. Furthermore, by combining the high-V OC perovskite solar cell with a c-Si solar cell, we demonstrate a perovskite−Si four-terminal tandem solar cell with a PCE of 27.1%, exceeding the record PCE of single-junction Si solar cells.