Forming a Metal-Free Oxidatively Coupled Agent, Bicarbazole, as a Defect Passivation for HTM and an Interfacial Layer in a p–i–n Perovskite Solar Cell Exhibits Nearly 20% Efficiency

Abstract

In this study, we synthesized three simple and inexpensive (34−120 USD/g) 3,3′-bicarbazole-based hole transporting materials (BC-HTMs; NP-BC, NBP-BC and PNP-BC) through a metal-free oxidative coupling, in excellent yields (≥95%). These bicarbazoles contain phenylene or biphenylene substituents on the carbazole N atom, with extended π-conjugation achieved through phenylene units at the 6,6′-positions of the bicarbazole. When using NBP-BC as a dopant-free HTM in a p−i−n perovskite solar cell (PSC), we achieved a power conversion efficiency (PCEs) of 12.22 ± 0.54% under AM 1.5G conditions (100 mW cm −2 ); this PCE was comparable to that obtained when using PEDOT:PSS as the HTM (11.23 ± 1.02%). BC-HTMs showed the large grain size (μm) of perovskite than PEDOT:PSS-based, due to defect passivation on indium tin oxide (ITO) substrate and good hydrophobicity. Furthermore, we realized highly efficient and stable PSCs when using the p−i−n device structure ITO/NiO x /NP-BC/perovskite/PC 61 BM/BCP/Ag. The bifacial defect passivation effect of the interfacial layer improved the grain size of the perovskite layer and also enhanced the performance; the best performance of the NiO x /NP-BC device was characterized by a short-circuit current density (J sc ) of 22.38 mA cm −2 , an open-circuit voltage (V oc ) of 1.09 V, and a fill factor (FF) of 79.9%, corresponding to an overall PCE of almost 20%. This device structure has competitive potential because its performance is comparable to that of the record-high-efficiency PSCs. Under an Ar atmosphere, the PCE of the NiO x /NP-BC PSC device decayed by only 4.55% after 168 h; it retained 90.80% of its original PCE after 1000 h. A morphological study revealed that the films of the BC-HTMs were indeed smooth and hydrophobic and that the perovskite films spin-coated upon them were uniform and featured large grains (micrometer scale). Time-resolved photoluminescence (TRPL) spectra of the perovskite films suggested that the hole extraction capabilities of the NiO x /BC-HTMs were better than that of the bare NiO x . The superior film morphologies of the NiO x /BC-HTMs were responsible for the performances of their devices being comparable to those of bare NiO x -based PSCs.

Spherical Hole-Transporting Interfacial Layer Passivated Defect for Inverted NiOx-Based Planar Perovskite Solar Cells with High Efficiency of over 20%

“…In our previous studies, we reported that the change in the HTM surface energy may affect the solid surface morphology during the heterogeneous nucleation, especially the carbazole-based derivatives, which have a significant effect. 22,23 The performances of the p−i−n PSCs of the embedded MSs and the control reference of the bare NiO x are summarized in Table 2. The control NiO x device had PCE of 17.55 ± 0.41%, with J sc of 21.43 ± 0.30 mA cm −2 , V oc of 1.08 ± 0.02 V, and FF of 75.9 ± 1.13%.…”

“…18−21 In our previous studies, we demonstrated 3,3′bicarbazole-and carbazole-based HTMs as interfacial layers with good defect passivation and improved perovskite film morphology in inverted PSCs. 22,23 The spiral HTMs assure excellent stability, good film morphology, and higher T g point. Much effort has been invested in researching suitable HTMs, such as spiro-OMeTAD, 24 spiro-acridine-fluorene, 25,26 spirobi[thieno [3,4b][1,4]dioxepine], 27 spiro[fluorene-9,9-xanthene], 4,28,29 dispiro-oxepine, 30 and spiro-phenylpyrazole-fluorine by replacing the spiro-core with a novel spiro-HTM structure.…”

“…31 However, the tedious synthesis process, high cost, and low charge carrier mobility of the HTM significantly limit their large-scale commercial applications. Today, high-efficiency and low-cost HTMs such as FDT, 32 X60, 29 Yih-2, 33 EDOT-Amide-TPA, 34 and NP-BC 22 have been reported for PSCs. These materials cost less than 40 USD/g and have shown a PCE ranging between 16.06 and 20.3%.…”

“…Carbazole-based materials possess superior charge-transporting ability and stability and are an efficient method to fine-tune electro-optical properties and are affordable. Additionally, their application in organic electronic organic light-emitting diodes (OLEDs), dye-sensitized solar cells (DSSCs), photovoltaic cells (OPVs), and PSCs have great potential. − These materials are often used because of their planar aromatic skeletons (good hole transporting), low oxidation potentials (electron-rich), and luminous behavior (singlet and triplet energies). − In our previous studies, we demonstrated 3,3′-bicarbazole- and carbazole-based HTMs as interfacial layers with good defect passivation and improved perovskite film morphology in inverted PSCs. , …”

Generation of Aryllithium Reagents from N-Arylpyrroles Using Lithium

“…]-2-yl)-2,5-diphenyl-1H-pyrrole (1l)26 1 H NMR (CDCl3): δ 7.41-7.38 (m, 1H), 7.32-7.27 (m, 2H), 7.23-7.22 (m, 1H), 7.13 (t, J = 7.2 Hz, 1H), 7.09-7.01 (m, 8H), 6.83 (m, 4H), 6.58-6.57 (m, 2H), 6.37 (s, 2H).13 C NMR (CDCl3): δ 139.9, 138.5, 136.5, 135.7, 133.2, 131.0, 130.4, 128.5, 128.1, 128.0, 127.97, 127.93, 127.8, 126.9, 126.0, 110.0. mp: 189-191 °C. HRMS (APCI-MS, positive): m/z = 372.1755. calcd for C28H22N: 372.1747[M+H] + .…”