Perovskite solar cells (PSCs) have attained considerable attention owing to their high-power conversion efficiency (PCE) and low manufacturing costs. However, the inadequate stability and lead leakage issues of PSCs remain as critical challenges impeding their practical implementation. In this work, we adopt an in situ self-polymerization strategy, with three monomers (N-Methylol acrylamide (NMA), N-(2-Hydroxypropyl) methacrylamide (2-HPMA), and N-(4-Hydroxyphenyl) methacrylamide (4-HPhMA)) introduced into the perovskite film. NMA and 2-HPMA undergo self-polymerization during the thermal annealing of the perovskite films, forming internal encapsulation within the perovskite film. In addition, the hydrogen bonding and chelating interactions between the perovskite and the polymers effectively suppress the defect states and significantly enhance the quality of perovskite films. Thus, the efficiency of devices increases from 22.41% to 25.06% after 2-HPMA modification. Moreover, the internal encapsulation effect induced by 2-HPMA endows PSCs with better long-term stability and humidity resistance. The unencapsulated device can retain 88% of its original PCE after storage in ambient air for 1000 h, and 86% of its pristine PCE after aging for 100 h at 60%‒80% relative humidity (RH) conditions. Furthermore, the interaction between the polymers and lead can largely inhibit lead leakage from unencapsulated PSCs.

The all-inorganic lead-free vacancy-ordered perovskite offers a promising avenue toward nontoxic and stable optoelectronic materials. Herein, we present a first-principles study of the structural stability, optical absorption, electronic structure, and mechanical behavior of Cs₂BCl₆ compounds with B-site substitutions (B＝Ge, Sn, Pb, Cr, Mo, W, Ti, Zr, and Hf). The structural analysis shows that the Cs₂BCl₆ perovskite with face-centered cubes has a stable chemical environment, especially Cs₂HfCl₆, Cs₂WCl₆, and Cs₂PbCl₆. Hf⁴⁺ and W⁴⁺ with high-energy d-state external electron configurations can further lower the valence band maximum position of the Cs₂BCl₆ structures and thus increase the band gap, assisting in tuning the optical absorption and emission properties of these structures in the optoelectronic application. For the light absorption properties of Cs₂BCl₆ materials, the best light absorption properties have been concluded for Ti⁴⁺, Cr⁴⁺, and Pb⁴⁺-based perovskite in the visible range due to a suitable band gap. Therefore, the excellent optical absorption and electronic properties make these vacancy-ordered perovskites promising candidates for optoelectronic applications.