Carbon Nanodot Additives Realize High‐Performance Air‐Stable p–i–n Perovskite Solar Cells Providing Efficiencies of up to 20.2%

Abstract

solar cells, and organic light emitting diodes. Because their perovskite precursors are commercially available, the study of PSCs has recently become an important emerging scientific field. [1] Today, the critical issues for PSC development are related to increasing their performance and stability. [2] Because the short-circuit current densities (J sc ) of PSC devices have almost approached their theoretical limit, efforts directed toward further increasing the performance have been based on increasing their open-circuit voltages (V oc ) and fill factors (FFs). Such approaches will necessitate optimizing the morphology, the interfacial layers, the device architectures, and the hole/electron transporting layers. [3] With advances in device engineering and materials, the power conversion efficiencies (PCEs) of PSCs have skyrocketed from 3.8% to 22.7% within the last six years. [1e,f,3c,4] Efforts at optimizing the morphologies of PSC films (i.e., their grain size, coverage, and crystallinity) have directly led to greater PSC performance. For example, variations in the solvents, thermal engineering techniques, and additives have all played roles in improving the quality of the resulting perovskite films. [5] Many types of additives-including metal/organic halide salts, solvents, Lewis bases, [6] inorganic acids, polymers, [7] and fullerenes-can enhance the morphologies and efficiencies of PSCs. [8] Considering the complexity of perovskite formation, the vast array of fabrication parameters, and the myriad materials that can be involved in the process, there remains plenty of room for new discoveries in this field.Because perovskite films are generally prepared through solution processes, the presence of defects-ones that cause nonradiative energy loss and decrease the values of V oc and efficiencies-is unavoidable. Tuning the composition to passivate the defects of perovskites (using such materials as pyridine [9] and polymers [8a] ) can be an efficient means of improving the performance of PSCs. In this present study, we employed carbon nanodots (CNDs) as additives that efficiently tailor the optoelectronic properties of perovskites. Because of their nanoscale dimensions, tunable optoelectronic properties, and ready synthesis (to present various functional groups), the study of CNDs has experienced rapid development, especially for Carbonized bamboo-derived carbon nanodots (CNDs) as efficient additives for application in perovskite solar cells (PSCs) are reported. These carboxylic acid-and hydroxyl-rich CNDs interact with the perovskite through hydrogen bonds and, thereby, promote the carriers' lifetimes and realize high-performance p-i-n PSCs having the structure indium tin oxide/ NiO x /CH 3 NH 3 PbI 3 (MAPbI 3 )/PC 61 BM/BCP/Ag. As a result of interactions between the CNDs and the perovskite, the presence of the nonvolatile CND additive increases the power conversion efficiency (PCE) of the PSC from 14.48% ± 0.39% to 16.47% ± 0.26%. Furthermore, adding urea, a Lewis base, increases the PCE to 20.2%-the re...

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“…[9] Urea has been used previously as an additive to promote the growth of largergrain perovskite crystals and, thereby, passivate the defects and improve the performance of PSC devices. [4] Thus, we prepared urea-derived devices to evaluate the effects of the grain size of the perovskite and the thickness of the perovskite layer on the performance. Table S2, Supporting Information, and Table 1 reveal that the PCEs of normal (perovskite thickness: 480 nm) urea-NiO x devices were 17.1 ± 1.13% with a dark current of 7.68 × 10 −11 A.…”

“…Large grains are associated with less of a GB and fewer defects (typically exhibited in the GB); therefore, they suppress undesired carrier recombination, lower the density of trap-states, and decrease the leakage current. [4] Nevertheless, the dark currents of these devices remained too high (76.8 pA) for practical applications. It has been demonstrated previously that increasing the thickness of the conjugated molecule can improve the dark current of the diode.…”

Goethite Quantum Dots as Multifunctional Additives for Highly Efficient and Stable Perovskite Solar Cells

“…Furthermore, the binding energy of I 3d in perovskite with FeOOH QDs shows the negative shift compared with the pristine perovskite (Figure g), indicating that Fe element in FeOOH QDs as a Lewis acid can also coordinate with Lewis base I ion. Overall, the interaction between the FeOOH QDs and the perovskite is beneficial for retarding the formation of defects and reducing the number of trap states, leading to the efficient intercrystal carrier transport …”

3 D NiO Nanowall Hole‐Transporting Layer for the Passivation of Interfacial Contact in Inverted Perovskite Solar Cells

“…Typically, solution‐based NiO nanocrystals (NCs) have been adopted as suitable HTMs with merits of high transmittance, favorable bandgap and energy level alignment . Such NiO‐based devices exhibit excellent long‐term moisture and thermal stability .…”

“…Typically,s olution-based NiO nanocrystals (NCs) have been adopted as suitable HTMs with merits of high transmittance, favorable bandgap and energy level alignment. [11][12][13][14][15] Such NiObased devices exhibit excellent long-term moisture and thermal stability. [16][17][18] However,t oo ur knowledge, the majority of recentw ork has focusedo nd oping NiOt of urtheri mprovei ts intrinsicc onductivity for betterd evicep erformance.…”