Over the past few years, metal halide-based organic–inorganic hybrid perovskite solar cells (PSCs) have attracted widespread concern because of their adjustable bandgap, long charge diffusion length, excellent absorption coefficient, and low cost. (1) Up to the present, the power conversion efficiency (PCE) of the PSCs at the laboratory scale has climbed to 26.1%. (2) However, it remains challenging to extensively apply PSCs in the commercial field because of their poorer long-term stability toward moisture, light, and heat than traditional silicon-based photovoltaic technology. (3) Such instability is mainly caused by high density defects disorderly distributed in grain boundary and perovskite surfaces, (4) which facilitates trap-assisted nonradiative recombination (5) and thus seriously restricts the enhancement of the PCE and greatly affects the stability of the devices. (6) To solve this problem, it is of great importance to passivate these defects. Many attempts have been made to eradicate the undesired defects in PSCs through defect healing stratagems including interface engineering, (7) chemical deposition, (8) additive methods, (9) and grain boundary regulation. (10)

As is well-known, the formation of defects in perovskite is inevitable. (11) Additive engineering is considered by many scientists to be one of the most effective ways to passivate these defects. (12) A variety of additives, such as Lewis acid, Lewis base, (13) inorganic acid, fullerene derivatives, (14) etc. are widely studied, with the aim of preventing the formation of harmful defects and reducing the migration channels of ions, while suppressing unfavorable crystallization. (15) In contrast to highly volatile and diffusive small molecule additives in perovskite film, polymer agents, characterized by long-range order, excellent stability, and low volatility, are potentially superior. Polymers are able to more stably and reliably interact with perovskite grains, (16) which could lead to a long-lasting defect passivation effect. Numerous studies have shown that polymer additives not only reduce the formation of noxious defects but also regulate the crystallization process. (17) Zuo et al. explored polymers with various specific groups and proposed that the polymer/perovskite bonding interaction is the critical factor to influence the passivation. (18) However, most reported polymers containing a single type of functional group can only passivate positive defects (i.e., Pb ions), thereby limiting the improvement of device performance and stability. In this regard, further research is required to develop new-type polymer additives with particular functionalized groups that are capable of precisely regulating the interaction with various defect sites in the perovskite while simultaneously protecting perovskite thin films...

Figure 1. (a) The synthesis procedure of p(HEMA-co-DEAMA) and schematic illustration of the molecular interactions between the perovskite crystal and p(HEMA-co-DEAMA). (b) Pb 4f XPS and (c) I 3d XPS spectra of the PbI2 films without and with p(HEMA-co-DEAMA). (d) C 1s XPS and (e) N 1s XPS spectra of FAI without and with p(HEMA-co-DEAMA). (f) FTIR spectra of the PbI2 film and the p(HEMA-co-DEAMA)-doped PbI2 film. (g) FTIR spectra of the FAI film and the p(HEMA-co-DEAMA)-doped FAI film.