Functionalized dimethylammonium bromide boost inverted inorganic perovskite photovoltaics for 20.62 % efficiency

Inorganic perovskite solar cells (IPSCs) with tunable bandgaps and absence of volatile organic cations (methylamine (MA) and formamidine (FA)), have garnered significant attention from the researchers. However, perovskite thin films of inverted-IPSCs tend to form p-type Fermi level (EF) interfaces, resulting in band structure mismatch. In this work, a gradient percolation method was introduced to alleviate this phenomenon. The Dimethylammonium Bromide (DMABr) can passivate the defects and alter the EF of the perovskite films, shifting it towards further N-type compared to the untreated state. By spontaneously permeating into the perovskite films, DMABr enabled a gradient distribution of bias N-type EF, which facilitated charge carrier transport and reduced non-radiative recombination. As a result, the IPSCs fabricated under ambient air conditions attained a power conversion efficiency (PCE) of 20.62 %.