Chloride gradient render carrier extraction of hole transport layer for high Voc and efficient inverted organometal halide perovskite solar cell

A carrier transport layer and its interfacial effects on an organometal halide perovskite light harvesting layer play an influential factor in either photovoltaic performance or long-term stability of a perovskite solar cell (OHPSC). Although the understandings of the carrier transport layers and interfacial effects on regular structured OHPSCs have been explored, knowledge of an interface between hole transport layer of NiOx and perovskite in an inverted OHPSC is still necessary to be developed. Here, we performed a universal NiOx film with the sequential passivation strategy of NiCl2 (SPS-NiCl2 treatment) for either wide bandgap or narrow bandgap of OHPSCs. The SPS-NiCl2 treated NiOx film not only implements the passivation at the perovskite layer/NiOx film interface but also confers itself a gradient energy level of valance band inducing by chloride. Comprehensive characterizations reveal that the SPS-NiCl2 treated NiOx film suppresses non-radiative recombination at the interface and enlarges the splitting of the quasi-Fermi level at the interfaces. The photoconversion efficiency (PCE) of the champion device comprised of the SPS-NiCl2 treated NiOx film can achieve 19.53% with a record V-oc of 1.16 V, the lowest V-oc deficit of 390 mV in NiOx based inverted OHPSCs. The corresponding devices with encapsulation also exhibit superior long-term stability, and over 80% of initial PCE can be maintained after 1500 h damp-heat test. This study sheds the light on managing the interfacial issues of an inverted OHPSC and offers a feasible path to develop a universal hole transport layer for perovskite layers with different energy bandgap.

Automated summary

The study explores the interfacial issues of an inverted OHPSC by applying a universal NiOx film with a sequential passivation strategy of NiCl2. The treated NiOx film not only passivates the interface but also induces a gradient energy level of valance band, suppressing non-radiative recombination and enlarging the splitting of the quasi-Fermi level at the interfaces. This approach leads to a high photoconversion efficiency and superior long-term stability in NiOx based inverted OHPSCs.