Scalable Flexible Perovskite Solar Cells Based on a Crystalline and Printable Template with Intelligent Temperature Sensitivity

Abstract

The control of crystallization and printability of large‐area perovskite layers is crucial to facilitating their commercial development in flexible electronics. Considering the benefits of the liquid crystals with intelligent temperature sensitivity for the printable and crystalline template of a scalable perovskite film, a liquid crystal 4((6(acryloyloxy)hexyl)oxy)benzoic acid (6OBA) is introduced. The 6OBA shows a liquid crystal temperature range matching with the thermal annealing temperature of perovskite films. A desire printability of perovskite inks for scalable and homogeneous devices is guaranteed due to the fluidity of the 6OBA additive at room temperature. Moreover, the crystalline 6OBA promotes crystallization of perovskite films during the thermal annealing process, which can also release the residual stress of the whole layer. The optimized perovskite solar cells (PSCs) with 6OBA exhibit superior power conversion efficiency values of 19.87% for flexible devices (1.01 cm2) and 14.74% for flexible modules (25 cm2). The unencapsulated devices can maintain >90% of their original efficiency after 1500 h in the ambient atmosphere. Furthermore, the flexible PSCs exhibit outstanding bending resistance, retaining over 88% of their initial efficiency after 1000 bending cycles at a radius of 3 mm. This work provides a facile strategy for accelerating the development of flexible electronics.

Functional Layers of Inverted Flexible Perovskite Solar Cells and Effective Technologies for Device Commercialization

“…At present, the fabrication of large-area FPSCs with both high efficiency and stability is still in its infancy. [37,78,[195][196][197][198][199][200][201][202][203][204][205][206] A summary of large-area inverted FPSCs is illustrated in Table 7.…”

“…Among coating techniques, blade (including knife, shearing, and meniscus) coating refers to the method of sliding the preprepared ink into a wet film on the web with a moving blade. [86,204,206] A pictorial description of the process can be seen in Figure 16a. [208] Blade coating has been widely used in the field of inverted FPSCs.…”

“…[ 204 ] In order to achieve uniform crystallization and stress release of perovskite films in inverted FPSCs, Yang et al introduced a liquid crystal 4((6(acryloyloxy)hexyl)oxy)benzoic acid (6OBA) with liquid fluidity and crystal orientation into the precursor to fabricate high‐quality perovskite films. [ 206 ] The inverted flexible devices fabricated by blade‐coating technique exhibited PCEs of 19.87% (1 cm 2 ) and 14.74% (25 cm 2 ).…”

Strain Release and Defect Passivation in Formamidinium-Dominated Perovskite via a Novel in-Plane Thermal Gradient Assisted Crystallization Strategy

“…15−17 In this context, three approaches have been reported to mitigate the harmful tensile strain in the fabrication process of perovskite films: (i) decreasing the local crystal misorientation by optimizing the nucleation and film growth of the perovskite; 18 (ii) fabricating the perovskite films under a low-temperature procedure or reducing the gap of thermal expansion coefficients between the perovskite and the substrate; 19,20 various flexible chains to facilitate the release of residual strain at grain boundaries. 21,22 Despite their effectiveness in bringing down the tensile strain in perovskite films, these approaches possess limitations to further enhancing the efficiency and stability of PSCs. 23 Moreover, a high annealing temperature (e.g., 150 °C) is vital to promote sufficient conversion from δ phase to α phase of FAPbI 3 perovskite.…”

“…Recently, many reports have demonstrated that the tensile strain causes lattice distortion of the microscopic crystal structure, weakens the bonds, induces the defects, reduces the activation energy for ion migration, and further accelerates the degradation of perovskites. ,, The tensile strain is mainly caused by the heterogeneous crystallization of the polycrystalline perovskite and the thermal expansion mismatch (e.g., 3.70 × 10 –6 K –1 for glass, 9.86 × 10 –5 K –1 for α-FAPbI 3 ) between the perovskites and the substrates during the annealing process, which can hardly be modulated by the postannealing treatment. − Strain engineering has been developed as an efficient approach to enhance the performance and stability of PSCs, because it can affect the band structure of the perovskite, the formation energy of defects, the activation energies for halide ion migration, and the intrinsic stability of the photoactive perovskite phase. − In this context, three approaches have been reported to mitigate the harmful tensile strain in the fabrication process of perovskite films: (i) decreasing the local crystal misorientation by optimizing the nucleation and film growth of the perovskite; (ii) fabricating the perovskite films under a low-temperature procedure or reducing the gap of thermal expansion coefficients between the perovskite and the substrate; , (iii) utilizing additives with various flexible chains to facilitate the release of residual strain at grain boundaries. , Despite their effectiveness in bringing down the tensile strain in perovskite films, these approaches possess limitations to further enhancing the efficiency and stability of PSCs . Moreover, a high annealing temperature (e.g., 150 °C) is vital to promote sufficient conversion from δ phase to α phase of FAPbI 3 perovskite.…”