Significant Efficiency and Stability Enhancement of Flexible Perovskite Solar Cells Combining with Multifunctional Effects of a Natural Spice

Abstract

The numerous defect‐induced non‐radiative recombination losses and residual stress in the preparation of perovskite film greatly hinder the further improvement of the efficiency and stability of flexible perovskite solar cells (PSCs). Here, a natural spice 7‐amino‐4‐(trifluoromethyl)‐2‐benzopyrone (ATB) containing amino (─NH2), carbonyl (─C═O), and trifluoromethyl (─CF3) functional groups is introduced into the perovskite precursor solution, thereby preparing high‐quality perovskite film with low defect density. It is revealed that the utilization of ATB is beneficial to comprehensively passivate the defects and release the residual stress of perovskite film through the synergistic effect of functional groups, thereby improving the crystallinity and enhancing the carrier lifetime of perovskite film. Moreover, the introduction of ATB contributes to an improved energy levels alignment between the perovskite and adjacent layers, which facilitates fast carrier transport and suppresses the recombination loss in the flexible PSCs. Combined with the multifunctional effects of ATB, the target flexible and rigid PSCs with ATB modification yield remarkable photoelectric conversion efficiency (PCE) of 21.08% and 23.79%, respectively. More importantly, the ATB‐modified flexible device exhibits outstanding stability and retains 87.3% and 91.6% of the original efficiency after aging for 3000 h at 50 ± 5 relative humidity and 5000 bending cycles, respectively.

Enhanced Performance of Flexible Perovskite Solar Cells Enabled by ATB Passivator

“…This shift may be attributed to the formation of hydrogen bond between -NH 3+ and I – , providing evidence for the existence of bonding between perovskite and ATB. − In Figure d, the N 1s XPS peak of the ATB-modified film shifts to a higher bonding energy, probably due to the interaction of –CF 3 with the FA + in the perovskite, forming a hydrogen bond. This interaction may affect the electron cloud density of the N element. , The synthesized results of XPS tests demonstrate that ATB molecules establish strong molecular bonds with perovskite through a variety of functional groups, as depicted in Figure e. This advantageous effect on the perovskite film during the preparation process enhances their interfilm interactions, thereby helping to improve device stability …”

“…This indicates that the addition of ATB improves the charge transport between the charge transport layer and the absorber. This improvement may be attributed to enhanced surface states and passivation of nonradiative recombination defects …”

“…This interaction may affect the electron cloud density of the N element. 24,33 The synthesized results of XPS tests demonstrate that ATB molecules establish strong molecular bonds with perovskite through a variety of functional groups, as depicted in Figure 2e. This advantageous effect on the perovskite film during the preparation process enhances their interfilm interactions, thereby helping to improve device stability.…”

“…The notable improvement in the environmental stability of ATB-processed devices is attributed to the hydrophobic −CF 3 group contained in the ATB additive, which leads to the enhancement of the film's humidity resistance. 24 Additionally, the incorporation of ATB leads to a reduction in the number of film defects, thereby maintaining the integrity of the perovskite crystal structure. Furthermore, the addition of ATB suppresses ionic migration, contributing to the comprehensive enhancement of the devices' environmental stability.…”

Silane Doping for Efficient Flexible Perovskite Solar Cells with Improved Defect Passivation and Device Stability

“…The rough surface tends to generate a large number of nucleation sites, , leading to overcrystallization and the formation of multisized perovskite grains, which in turn affects the crystalline quality and morphology of the films. All those derived defects may become carrier complexation centers, causing nonradiative recombination losses and generating residual stresses, − thus reducing the power conversion efficiency (PCE) of the device, as the perovskite material in the light-absorbing layer is prone to absorbing moisture in the air, − leading to the production of defects from oxidation, which provide pathways for the infiltration of water and oxygen, accelerating the decomposition of the perovskite layer and degradation of devices . Therefore, the formation of high-quality perovskite films with dense, smooth surfaces and pinhole-free properties is crucial to realizing efficient devices.…”