Zwitterion Coordination Induced Highly Orientational Order of CH₃NH₃PbI₃ Perovskite Film Delivers a High Open Circuit Voltage Exceeding 1.2 V

Abstract

The organic-inorganic halide CH 3 NH 3 PbI 3 (MAPbI 3 ) has been the most commonly used light absorber layer of perovskite solar cells (PSCs); however, solution-processed MAPbI 3 films usually suffer from random crystal orientation and high trap density, resulting in inferior power conversion efficiency (PCE) with open circuit voltage (V oc ) being typically below 1.2 V for PSC devices. Herein, for the first time an imidazole sulfonate zwitterion, 4-(1H-imidazol-3-ium-3-yl)butane-1-sulfonate (IMS), is applied as a bifunctional additive in regular-structure planar heterojunction PSC devices to regulate the crystal orientation, yielding highly ordered MAPbI 3 film and passivating the trap states of the film. Such a dual effect of IMS is fulfilled via coordination interactions between the sulfonate moiety of IMS with the Pb2 + ion and the electrostatic interaction between the imidazole of IMS with the Iion of MAPbI 3 . As a result, under a optimized IMS doping ratio of 0.5 wt%, the PSC device exhibits a significant increase in PCE from 18.77% to 20.84%, with suppressed current-voltage hysteresis and promoted ambient stability. Moreover, a high V oc of 1.208 V is achieved under a higher IMS doping ratio of 1.2 wt%, which is the highest V oc for regular-structure MAPbI 3 planar PSC devices based on TiO 2 electron transport layer.

Grain Enlargement and Defect Passivation with Melamine Additives for High Efficiency and Stable CsPbBr3 Perovskite Solar Cells

“…Ac hampion power conversion efficiency as high as 9.65 %w ith ap romising open-circuit voltage of 1.584 Vi sa chieved for PSCs with an architecture of fluorinedoped tin oxide/c-TiO 2 /m-TiO 2 /melamine-addedC sPbBr 3 / carbon-based hole-transporting layer.F urthermore, the unencapsulated melamine-added CsPbBr 3 PSC shows superior thermal and humidity stabilityi na mbient air at 85 8Co r8 5% relative humidity over 720 h. functional additives into the precursor solution to obtain highquality perovskite films thougha djusting the crystallization dynamics and simultaneously to realize the passivationo fu ncoordinated ion defects. [15,16] Avariety of chemical additives, such as polymers, [15] ionic liquids, [17,18] inorganic or ammonium salts, [19,20] and nanoparticles [21] have been used as additives to achieve high-quality perovskite film synthesis. But the use of most additives is relativelym onotonous, for instance, the addition of Lewis acid or base, such as fullerene and its derivatives, [22,23] trioctylphosphine oxide, [24] poly(4-vinylpyridine), [25] can produce aL ewis adduct by opportunely coordinating with the harmful ionic defects, but cannot form ah igh-qualityf ilm morphology with large crystal grains by regulating the crystal growth process.…”

“…Yang and co-workersf irst used imidazole sulfonate zwitterion,4 -(1 H-imidazol-3-ium-3-yl)butane-1-sulfonate (IMS) as an additive to regulate the crystal orientation;t he PCE of the PSC increased significantly from 18.77 %t o2 0.84 %o wing to the preparation of ah ighly ordered MAPbI 3 film with fewer defects. [19] Huang and colleagues designed an ew passivation molecule of d-4-tert-butylphenylalanine( D4TBP) and added it to the precursor solution to form high-crystallinity perovskite films with appropriate grain size and reduced defect states, resulting in an enhanced PCE of up to 21.4 %o ft he p-i-n structure PSCs. [30] Evidently,i ti sa ne ffective route to employ an additivew ith N-based polyfunctional group to build perovskite films with low grain boundaries and defects for high-efficiency PSCs.…”

Surface Passivation of Perovskite Film by Sodium Toluenesulfonate for Highly Efficient Solar Cells

“…Up to now several approaches have been developed to passivate the defects at the surface of perovskite film, including solvent annealing, additive engineering, post‐treatment, and surface modification . In particular, surface modification fulfilled by depositing a modifier layer atop the perovskite layer is facile with no need to change the fabrication process of the perovskite layer and thus has been extensively utilized .…”

Enhanced Crystallinity of Triple-Cation Perovskite Film via Doping NH4SCN

“…The perovskite films with less crystal grain boundary area can be obtained via increasing the crystal grain size. To enlarge the crystal grain size of perovskite films, various methods have been developed, including the additive engineering [13][14][15], precursor solvent engineering [16], anti-solvent engineering [17], and procedure optimization [18][19][20]. Among these methods, the additive engineering is one of the most frequently used methods to the realization of large-crystal-grain-size perovskite films.…”

“…Among these methods, the additive engineering is one of the most frequently used methods to the realization of large-crystal-grain-size perovskite films. The additive materials include polymers [21], small organic molecules [15,22], and inorganic salts [23]. The polymers with special organic groups like carbonyl groups can slow down the crystallization process and enlarge the grain size of the perovskite films [21].…”