This paper discusses a series of triphenylamine dibenzofulvene–based hole transporting materials (HTMs) featuring different numbers of MeO groups (none for YC‐1, four for YC‐2, and six for YC‐3) and their use in p‐i‐n perovskite solar cells (PSCs). We investigated the optoelectronic properties of these HTMs and found that the PSC devices incorporating YC‐1 as HTMs exhibited power conversion efficiencies (PCEs) of 15.78 ± 0.61%, which outperformed the corresponding PEDOT:PSS‐based device (12.80 ± 1.31%) under similar testing conditions. We then employed YC‐1 for the interfacial modified layer of a NiOx‐derived PSC having the structure ITO/NiOx/YC‐1/CH3NH3PbI3/PC61BM/bathocuproine/Ag. The presence of YC‐1 promoted the growth of micrometer‐sized grains of perovskite and induced a lower content of grain boundary defects, both of which improved the carrier extraction. Thereby, compared with conventional NiOx device, we observed a great increase in the PCE, from 17.16 ± 0.68% to 18.81 ± 0.42%, with a champion cell displaying a PCE of 19.37% (with negligible hysteresis). The corresponded device exhibited a stabilized efficiency of approximately 19% after storage in the dark at 25°C under argon for over 1000 hours. This study suggests a new approach for designing the high‐performance stable p‐i‐n PSCs.

In this study, we synthesized four acceptor–donor–acceptor type hole-transporting materials (HTMs) of SY1–SY4 for an HTMs/interfacial layer with carbazole as the core moiety and ester/amide as the acceptor unit. These HTMs contain 4-hexyloxyphenyl substituents on the carbazole N atom, with extended π-conjugation achieved through phenylene and thiophene units at the 3,6-positions of the carbazole. When using amide-based HTMs SY2 as a dopant-free HTM in a p–i–n perovskite solar cell (PSC), we achieved a power conversion efficiency (PCE) of 13.59% under AM 1.5G conditions (100 mW cm–2); this PCE was comparable with that obtained when using PEDOT:PSS as the HTM (12.33%). Amide-based SY2 and SY4 HTMs showed a larger perovskite grain than SY1 and SY3 because of the passivation of traps/defects at the grain boundaries and stronger interaction with the perovskite layer. In further investigation, we demonstrated highly efficient and stable PSCs when using the dopant-free p–i–n device structure indium tin oxide/NiO x /interfacial layer (SY-HTMs)/perovskite/PC61BM/BCP/Ag. The interfacial layer improved the PCEs and large grain size (micrometer scale) of the perovskite layer because of defect passivation and interface modification; the amide group exhibited a Lewis base adduct property coordinated to Ni and Pb ions in NiO x and perovskite, bifacial defect passivation and reduced the grain boundaries to improve the crystallinity of the perovskite. The amide-based SY2 exhibited the stronger interaction with the perovskite layer than that of ester-based SY1, which is related to the observations in X-ray absorption near edge structure (XANES). The best performance of the NiO x /SY2 device was characterized by a short-circuit current density (J sc) of 21.76 mA cm–2, an open-circuit voltage (V oc) of 1.102 V, and a fill factor of 79.1%, corresponding to an overall PCE of 18.96%. The stability test of the PCE of the NiO x /SY2 PSC device PCE showed a decay of only 5.01% after 168 h; it retained 92.01% of its original PCE after 1000 h in Ar atmosphere. Time-resolved photoluminescence spectra of the perovskite films suggested that the hole extraction capabilities of the NiO x /SY-HTMs were better than that of the bare NiO x . The superior film morphologies of the NiO x /SY-HTMs were responsible for the performances of their devices being comparable with those of bare NiO x -based PSCs. The photophysical properties of the HTMs were analyzed through time-dependent density functional theory with the B3LYP functional.

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.

In this study, a series of 2,2′ and 3,3′ substituted thienoisoindigo (TII)-based small molecules (H3–H7) were synthesized by using 1,3-di­(9H-carbazol-9-yl) benzene, N-phenylcarbazole, triphenylamine, and benzene as electron donor (D) at the periphery, while TII as electron acceptor (A) at the core. The highest occupied molecular orbital energy levels of H3–H7 range from −5.31 to −5.43 eV, while their lowest unoccupied molecular orbital energy levels range from −3.43 to −3.59 eV. Under AM 1.5 condition, the perovskite solar cell (PSC) with inverted p–i–n device structure using H7 as the dopant-free hole transporting material achieved a power conversion efficiency (PCE) of 12.1%, which is comparable to that using PEDOT:PSS as the hole transporting material (12.0%). Under an argon atmosphere, the PCE of H7-based PSC did not decay within 168 h, and it can retain 86.3% of its original PCE after 1000 h. The morphology study revealed that the film of H3–H7 was smooth and hydrophobic, while the perovskite film spin-coated on H3–H7 film was uniform with the grain size in micrometer scale. Although the time-resolved photoluminescence spectra of the perovskite films suggested that the hole extraction capability of H7 is weaker than that of PEDOT:PSS, the improved film morphology of the film in H7-based PSC accounts for its comparable PCE to PEDOT:PSS-based PSC.

In this study, we prepared DPPBTDA, a diketopyrrolopyrrole-based small molecule presenting a terminal cross-linkable azido group, as a cathode modifying layer for organic photovoltaics (OPVs) having the inverted device structure glass/indium tin oxide/zinc oxide (ZnO) with or without the interfacial layer (IFL)/active layer/MoO/Ag. The active layer comprising a blend of poly[4,8-bis(5-(2-ethylhexyl)thien-2-yl)benzo[1,2- b;4,5- b']dithiophene-2,6-diyl- alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4- b]thiophene)-2-carboxylate-2,6-diyl] (PTB7-Th) as the electron donor and [6,6]-phenyl-C-butyric acid methyl ester (PCBM) as the electron acceptor. Atomic force microscopy, space-charge-limited current mobility, surface energy, electron spectroscopy for chemical analysis depth profile, ultraviolet photoelectron spectroscopy analysis, and OPV performance data revealed that the surface status of ZnO changed after inserting the DPPBTDA/PCBM hybrid IFL and induced an optimized blend morphology, having a preferred gradient distribution of the conjugated polymer and PCBM, for efficient carrier transport. The power conversion efficiency (AM 1.5 G, 1000 W m) of the device incorporating the hybrid IFL increased to 9.4 ± 0.11% from 8.5 ± 0.15% for the preoptimized PTB7-Th/PCBM device (primarily because of an enhancement in the fill factor from 68.7 ± 1.1 to 72.1 ± 0.8%).