Because of their straightforward manufacture and exceptional photovoltaic efficiency, perovskite solar cells (PSCs) have quickly become appealing rivals in the photovoltaic sector. The residual strain, which prevents their practical use, keeps the efficiency and long‐term stability below practical bounds. Herein, the causes of strain in metal‐halide perovskites that are pertinent to photovoltaic applications, as well as how strain affects the materials’ physical characteristics and solar performance and how to control it, are discussed. Finally, a perspective on future strain engineering to support robust and effective PSCs is proposed. This review provides a comprehensive understanding of strain from origins, effects, to regulation, which would enhance the research enthusiasm on strain engineering to drive further improvements in performance especially stability of PSCs toward commercialization.

Thermoelectric (TE) technology, which can convert scrap heat into electricity, has attracted considerable attention. However, broader applications of TE are hindered by lacking high-performance thermoelectric materials, which can be effectively progressed by regulating the carrier concentration. In this work, a series of PbSe(NaCl)x (x = 3, 3.5, 4, 4.5) samples were synthesized through the NaCl salt-assisted approach with Na+ and Cl− doped into their lattice. Both theoretical and experimental results demonstrate that manipulating the carrier concentration by adjusting the content of NaCl is conducive to upgrading the electrical transport properties of the materials. The carrier concentration elevated from 2.71 × 1019 cm−3 to 4.16 × 1019 cm−3, and the materials demonstrated a maximum power factor of 2.9 × 10−3 W m−1 K−2. Combined with an ultralow lattice thermal conductivity of 0.7 W m−1 K−1, a high thermoelectric figure of merit (ZT) with 1.26 at 690 K was attained in PbSe(NaCl)4.5. This study provides a guideline for chemical doping to improve the thermoelectric properties of PbSe further and promote its applications.