Open-circuit and short-circuit loss management in wide-gap perovskite p-i-n solar cells

In this work, we couple theoretical and experimental approaches to understand and reduce the losses of wide bandgap Br-rich perovskite pin devices at open-circuit voltage (V(OC)) and short-circuit current (J(SC)) conditions. A mismatch between the internal quasi-Fermi level splitting (QFLS) and the external V(OC) is detrimental for these devices. We demonstrate that modifying the perovskite top-surface with guanidinium-Br and imidazolium-Br forms a low-dimensional perovskite phase at the n-interface, suppressing the QFLS-V(OC) mismatch, and boosting the V(OC). Concurrently, the use of an ionic interlayer or a self-assembled monolayer at the p-interface reduces the inferred field screening induced by mobile ions at J(SC), promoting charge extraction and raising the J(SC). The combination of the n- and p-type optimizations allows us to approach the thermodynamic potential of the perovskite absorber layer, resulting in 1 cm(2) devices with performance parameters of V(OC)s up to 1.29 V, fill factors above 80% and J(SC)s up to 17 mA/cm(2), in addition to a thermal stability T(80) lifetime of more than 3500 h at 85 °C.