Dual function interfacial layer for highly efficient and stable lead halide perovskite solar cells

The trap states and the intrinsic nature of polycrystalline organometallic perovskites cause carrier losses in perovskite solar cells (PSCs) through carrier recombination at the surface and subsurface of the perovskites, leading to lowered conversion efficiency. Herein, to reduce the carrier losses, an intelligent approach concerning surface passivation and interfacial doping of the perovskite is proposed by introducing an F4TCNQ interfacial layer. The trap states at the perovskite surface are efficiently suppressed, leading to a homogenous surface potential of perovskite, which avoids the surface carrier recombination. The Fermi level of the perovskite is shifted to its valence band by 0.2 eV, inducing an energy barrier for electron diffusion and contributing directly to a minimized carrier recombination at the subsurface of the perovskite film. Consequently, the performance of the PSCs is remarkably improved, with the average efficiency increased from 14.3 +/- 0.9% to 16.4 +/- 1.0% (with a maximum efficiency of 18.1%). Moreover, the PSCs with the dual function interfacial layer show enhanced long-term stability in ambient air without device encapsulation.