Introducing excessive PbI 2 in perovskite is widely used to fabricate high performance perovskite solar cells (PSCs) via two-step spin coating , whereas the photoinduced decomposition of excessive PbI 2 may induce perovskite photodegradation for long-term illumination. In this work, a Lewis base semicarbazide hydrochloride (SH) is introduced in the first-step PbI 2 film, which can anchor strongly PbI 2 at the grain boundaries of perovskite, suppressing its photoinduced decomposition to Pb 0 and I 2 , and consequently enhancing the long-term photostability of PSCs. In addition, it is verified that SH can also coordinate with the uncoordinated Pb 2+ in perovskite, and thus stabilize [PbX 6 ] 4- octahedral to inhibit photoinduced ion migration. Therefore, the optimized PSC exhibits not only an improved power conversion efficiency (PCE) of 21.88%, but also an enhanced photostability with 82.8% of its initial PCE under 500 h continuous AM 1.5G illumination. This work provides a new strategy to suppress PbI 2 photoinduced decomposition and perovskite photodegradation for the realization of photostable and efficient PSCs.
Hybrid organic-inorganic perovskites (HOIPs) exhibit long electronic carrier diffusion length, high optical absorption coefficient, and impressive photovoltaic device performance. At the core of any optoelectronic device lie the charge transport properties, especially the microscopic mechanism of scattering, which must efficiently affect the device function. In this work, CH 3 NH 3 PbI 3 (MAPbI 3 ) films were fabricated by a vapor solution reaction method. Temperature-dependent Hall measurements were introduced to investigate the scattering mechanism in MAPbI 3 films. Two kinds of temperature-mobility behaviors were identified in different thermal treatment MAPbI 3 films, indicating different scattering mechanisms during the charge transport process in films. We found that the scattering mechanisms in MAPbI 3 films were mainly influenced by the decomposed PbI 2 components, which could be easily generated at the perovskite grain boundaries (GBs) by releasing the organic species after annealing at a proper temperature. The passivation effects of PbI 2 in MAPbI 3 films were investigated and further discussed with emphasis on the scattering mechanism in the charge transport process.
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