Evening out the heat: The conversion of precursors into the active layer of perovskite solar cells normally occurs by heating the underlying substrate. Conversion tends to occur near the top of the film, where solvent is lost, and unwanted preheating of reactants occurs near the substrate before the reaction. Li et al . show that the use of a surrounding heat transfer oil (anisole) leads to more rapid and even heating, removes solvent, and avoids air and water contamination effects. The larger grains and more uniform films led a much greater retention of efficiency in moving from small-area to large-area devices. —PDS

We develop a general and unified first-principles theory of piezoelectric and flexoelectric tensor, formulated in such a way that the tensor elements can be computed directly in the context of density-functional calculations, including electronic and lattice contributions. We introduce practical supercell-based methods for calculating the flexoelectric coefficients from first principles, and demonstrate them by computing the coefficients for a variety of cubic insulating materials including C, Si, MgO, NaCl, CsCl, BaZrO${}_{3}$, BaTiO${}_{3}$, PbTiO${}_{3}$, and SrTiO${}_{3}$.

Long-term stability is an essential requirement for perovskite solar cells (PSCs) to be commercially viable. Heterojunctions built by low-dimensional and three-dimensional perovskites (1D/3D or 2D/3D) help to improve the stability of PSCs. However, the insulated organic cations of low-dimensional perovskite impede the transport of carriers, decreasing the power conversion efficiency (PCE) of PSCs. Herein, we introduce an in situ cross-linking polymerizable propargylammonium (PA⁺) to the 3D perovskite film at surfaces and grain boundaries to form a 1D/3D perovskite heterostructure. This passivation strategy not only significantly improves the interfacial carrier transport but also releases residual tensile strain in perovskite films. As a result, the corresponding devices achieve a champion PCE of 21.19%, while maintaining 93% of their initial efficiency after 3055 h of continuous illumination under maximum power point (MPP) operating conditions.