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Mixed lead‐tinv halide (LTH) perovskite solar cells (LTH‐PSCs) can reduce the toxicity concerns of full lead‐based PSCs and potentially optimize the bandgap to maximize efficiency. However, commonly used hole‐transporting material (HTM) 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenyl‐amine)9,9′‐spirobifluorene (Spiro‐OMeTAD) with additional dopants Li‐bis(trifluoromethanesulfonyl) imide (Li‐TFSI) and 4‐tert‐butylpyridine (t‐BP) deteriorate oxidation Sn2+ to Sn4+ leading to trap formation. Here, the study introduces a novelty Sn‐friendly HTM for Sn‐rich LTH‐PSCs, combining Spiro‐OMeTAD with 4‐Isopropyl‐4′‐methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (dpi‐TPFB) as a dopant and blended with poly(3‐hexylthiophene‐2,3‐diyl) (P3HT). This blended HTM avoids the harmful effects of Li‐TFSI and t‐BP dopants and leverages the beneficial hydrophobic properties of P3HT, which predominantly resides on the surface with a face‐on orientation. This arrangement not only enhances charge transport and extraction but also improves device stability by protecting the perovskite from environmental factors. Optimizing the P3HT concentration of blended HTM achieved a PCE of 17.27%, the highest reported for n‐i‐p structured Sn‐rich mixed LTH‐PSCs. This HTM also significantly improved device stability, maintaining over 90% of the initial PCE after 3000 h of storage and 80% under maximum power point tracking (MPPT) for 550 h in the air. [ABSTRACT FROM AUTHOR]

Alkyl‐primary‐ammonium‐based room‐temperature ionic liquids (RTILs) designed to exhibit specific reactivities allowing functions that cannot be achieved by other RTILs have recently emerged. The archetype of the reactive RTILs is n‐octylammonium bis(trifluoromethanesulfonyl)imide (OA‐TFSI), which has promising functions as an additive for hole transport materials (HTMs) in perovskite solar cells (PSCs); the high reactivity of the OA cations on the perovskite surface allows spontaneous perovskite passivation via HTM deposition, effectively improving the photovoltaic (PV) performance. However, although the reactivity manipulation of the reactive RTILs is instrumental for exploiting their potential functions and exploring their application scope, methods for reactivity control have not been developed. Herein, it is proposed that the coaddition of a pyridine derivative (4‐tert‐butylpridine: TBP) can effectively manipulate the reactivity of OA‐TFSI by controlling the protonation between OA and the 2,2′,7,7′‐tetrakis‐(N,N‐di‐4‐methoxyphenylamino)‐9,9′‐spirobifluorene (Spiro‐OMeTAD) HTM. The TBP prevents OA deprotonation presumably via stabilization of the OA cation, thus retaining its ammonium form, which allows efficient spontaneous perovskite passivation, effectively enhancing the PV performance. This reveals the protonation preference in the OA‐TFSI system, which is opposite to that in conventional RTILs. This first proposal of a method in manipulating reactivity of the reactive RTILs will contribute to the development of materials science. [ABSTRACT FROM AUTHOR]

Electron donor (D)-electron acceptor (A) type conjugated polymers present bright prospects as dopant-free hole-transporting materials (HTMs) for perovskite solar cells (PVSCs). Most of the reported D-A polymeric HTMs contain equivalent amounts of D and A units, while the appropriate excess proportion of D units could optimize the aggregation state of polymer chains and improve the hole transport properties of the polymers. Herein, a non-equivalent D-A copolymerization strategy was utilized to develop three indacenodithiophene-benzotriazole-based polymeric HTMs for PVSCs, named as F-10, F-15, and F-20, and the equivalent D-A polymer F-00 was studied in parallel. Effects of D:A ratio on the hole transport properties of these D-A type polymeric HTMs, including energy level, molecular stacking, hole mobility, and surface morphology, were investigated by theoretical simulation and test analysis. F-15 performed best due to the appropriate D:A ratio, endowing the PVSCs a champion power conversion efficiency of 20.37% with high stability, which confirms the fine-tuning D:A ratio via non-equivalent D-A copolymerization strategy is very helpful to construct D-A type polymeric HTMs for highperformance PVSCs. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) offer advantages over widely deployed silicon solar cells in terms of ease of fabrication; however, the device is still under rigorous materials optimization for cell performance, stability, and cost. In this work, we explore a version of a PSC by replacing the polymeric hole transport layer (HTL) such as Spiro-OMeTAD, P3HT, and PEDOT: PSS with a more air-stable metal oxide, viz., nitrogen-doped titanium dioxide (TiO2:N). Numerical simulations on formamidinium (FA)-based PSCs in the FTO/TiO2/FAPbI3/Ag configuration have been carried out to depict the behaviour of the HTL as well as the effect of absorber layer thickness (∆t) on photovoltaic parameters. The results show that the cell output increases when the HTL bandgap increases from 2.5 to 3.0 eV. By optimizing the absorber layer thickness and the gradient in defect density (Nt), the device structure considered here can deliver a maximum power conversion efficiency of ~21.38% for a lower HTL bandgap (~2.5 eV) and ~26.99% for a higher HTL bandgap of ~3.0 eV. The results are validated by reproducing the performance of PSCs employing commonly used polymeric HTLs, viz. Spiro-OMeTAD, P3HT, and PEDOT: PSS as well as high power conversion efficiency in the highly crystalline perovskite layer. Therefore, the present study provides high-performing, cost-effective PSCs using TiO2:N. [ABSTRACT FROM AUTHOR]

Electron donor (D)-electron acceptor (A) type conjugated polymers present bright prospects as dopant-free hole-transporting materials (HTMs) for perovskite solar cells (PVSCs). Most of the reported D-A polymeric HTMs contain equivalent amounts of D and A units, while the appropriate excess proportion of D units could optimize the aggregation state of polymer chains and improve the hole transport properties of the polymers. Herein, a non-equivalent D-A copolymerization strategy was utilized to develop three indacenodithiophene-benzotriazole-based polymeric HTMs for PVSCs, named as F-10, F-15, and F-20, and the equivalent D-A polymer F-00 was studied in parallel. Effects of D : A ratio on the hole transport properties of these D-A type polymeric HTMs, including energy level, molecular stacking, hole mobility, and surface morphology, were investigated by theoretical simulation and test analysis. F-15 performed best due to the appropriate D : A ratio, endowing the PVSCs a champion power conversion efficiency of 20.37 % with high stability, which confirms the fine-tuning D : A ratio via non-equivalent D-A copolymerization strategy is very helpful to construct D-A type polymeric HTMs for high-performance PVSCs., (© 2024 Wiley-VCH GmbH.)

Perovskite solar cells (PSCs) offer advantages over widely deployed silicon solar cells in terms of ease of fabrication; however, the device is still under rigorous materials optimization for cell performance, stability, and cost. In this work, we explore a version of a PSC by replacing the polymeric hole transport layer (HTL) such as Spiro-OMeTAD, P3HT, and PEDOT: PSS with a more air-stable metal oxide, viz., nitrogen-doped titanium dioxide (TiO2:N). Numerical simulations on formamidinium (FA)-based PSCs in the FTO/TiO2/FAPbI3/Ag configuration have been carried out to depict the behaviour of the HTL as well as the effect of absorber layer thickness (∆t) on photovoltaic parameters. The results show that the cell output increases when the HTL bandgap increases from 2.5 to 3.0 eV. By optimizing the absorber layer thickness and the gradient in defect density (Nt), the device structure considered here can deliver a maximum power conversion efficiency of ~21.38% for a lower HTL bandgap (~2.5 eV) and ~26.99% for a higher HTL bandgap of ~3.0 eV. The results are validated by reproducing the performance of PSCs employing commonly used polymeric HTLs, viz. Spiro-OMeTAD, P3HT, and PEDOT: PSS as well as high power conversion efficiency in the highly crystalline perovskite layer. Therefore, the present study provides high-performing, cost-effective PSCs using TiO2:N.

Abstract Environmentally benign and potentially cost‐effective Sb2Se3 solar cells have drawn much attention by continuously achieving new efficiency records. This article reports a compatible strategy to enhance the efficiency of planar n–i–p Sb2Se3 solar cells through Sb2Se3 surface modification and an architecture with oriented 1D van der Waals material, trigonal selenium (t‐Se). A seed layer assisted successive close spaced sublimation (CSS) is developed to fabricate highly crystalline Sb2Se3 absorbers. It is found that the Sb2Se3 absorber exhibits a Se‐deficient surface and negative surface band bending. Reactive Se is innovatively introduced to compensate the surface Se deficiency and form an (101) oriented 1D t‐Se interlayer. The p‐type t‐Se layer promotes a favored band alignment and band bending at the Sb2Se3/t‐Se interface, and functionally works as a surface passivation and hole transport material, which significantly suppresses interface recombination and enhances carrier extraction efficiency. An efficiency of 7.45% is obtained in a planar Sb2Se3 solar cell in superstrate n–i–p configuration, which is the highest efficiency for planar Sb2Se3 solar cells prepared by CSS. The all‐inorganic Sb2Se3 solar cell with t‐Se shows superb stability, retaining ≈98% of the initial efficiency after 40 days storage in open air without encapsulation.

In the conventional n-i-p structure of perovskite solar cell (PSC), spiro-OMeTAD is used as the hole transport layer. However, some additives in spiro-OMeTAD, such as LiTFSI and TBP, can bring risks for perovskite degradation. Nickel oxide (NiO), a wide-band gap (3.6–4.0 eV) p-type semiconductor material with excellent electrical and optical properties, is widely applied in the PSCs and other fields. Given the suitable valence and conduction bands, NiO can effectively block electrons and transport holes, which are generated in the perovskite film after illumination. However, depositing a compact and thin NiO layer on the perovskite film is difficult because of the heat and solvent sensitivity of organic–inorganic hybrid perovskite. Here, we propose a facile method to prepare well-dissolved NiO nanoparticles in chlorobenzene, and the NiO film on perovskite is further modified by oxygen plasma or hexanethiol treatment to enhance the hole conductivity. Finally, we obtain a n-i-p structured PSC on the basis of all-inorganic charge transport layer with an efficiency of 4.21% using the prepared NiO film, and the value is further improved to 6.10% after oxygen plasma post-treatment. Moreover, the working stability is enhanced remarkably as the spiro-OMeTAD is replaced by NiO film, which is important for the application of PSCs. [ABSTRACT FROM AUTHOR]

Environmentally benign and potentially cost‐effective Sb2Se3 solar cells have drawn much attention by continuously achieving new efficiency records. This article reports a compatible strategy to enhance the efficiency of planar n–i–p Sb2Se3 solar cells through Sb2Se3 surface modification and an architecture with oriented 1D van der Waals material, trigonal selenium (t‐Se). A seed layer assisted successive close spaced sublimation (CSS) is developed to fabricate highly crystalline Sb2Se3 absorbers. It is found that the Sb2Se3 absorber exhibits a Se‐deficient surface and negative surface band bending. Reactive Se is innovatively introduced to compensate the surface Se deficiency and form an (101) oriented 1D t‐Se interlayer. The p‐type t‐Se layer promotes a favored band alignment and band bending at the Sb2Se3/t‐Se interface, and functionally works as a surface passivation and hole transport material, which significantly suppresses interface recombination and enhances carrier extraction efficiency. An efficiency of 7.45% is obtained in a planar Sb2Se3 solar cell in superstrate n–i–p configuration, which is the highest efficiency for planar Sb2Se3 solar cells prepared by CSS. The all‐inorganic Sb2Se3 solar cell with t‐Se shows superb stability, retaining ≈98% of the initial efficiency after 40 days storage in open air without encapsulation. [ABSTRACT FROM AUTHOR]

Thin-film solar cells have attracted worldwide attention due to their high efficiency and low cost. Antimony selenide (Sb 2 Se 3) is a promising light absorption material candidate for thin-film solar cells due to its suitable band gap, abundance, low toxicity, and high chemical stability. Herein, we fabricate an Sb 2 Se 3 thin film solar cell using a simple hydrazine solution process. By controlling the thickness of the photoactive layer and inserting a poly(3-hexylthiophene) hole-transporting layer, an Sb 2 Se 3 solar cell with a power conversion efficiency of 2.45% was achieved. To improve high-efficiency Sb 2 Se 3 thin-film solar cells, an n-i-p structure was designed using the optimized thickness control of the light absorption layer and a poly(3-hexylthiophene) hole-transporting layer. Image 1 • As the photoactive layer of solar cell, Sb 2 Se 3 thin-films were fabricated using solution process. • The thickness of the Sb 2 Se 3 photoactive layer was optimized by repeating the deposition process. • Improved efficiency of Sb 2 Se 3 solar cell was achieved by introducing poly(3-hexylthiophene) as a hole-transporting layer. [ABSTRACT FROM AUTHOR]

High performance, hysteresis-free, low temperature n-i-p perovskite solar cells are successfully fabricated by solution processing using fullerene electron transport layer (ETL). PC 71 BM fullerene, with broader absorption spectrum and lower HOMO level, when incorporated in the perovskite solar cell yielded average power conversion efficiency (PCE) of 13.9%. This is the highest reported PCE in n-i-p perovskite solar cells with PC 71 BM ETL. The devices exhibited negligible hysteresis and high open-circuit voltage (V oc ). On the contrary, devices with PC 61 BM, a common fullerene ETL in perovskite solar cell, exhibited large hysteresis and lower V oc . The underlying mechanisms of superior performance of devices with PC 71 BM ETL were found to be correlated with fullerene surface wettability and perovskite grain size. The influence of fullerene ETL on the perovskite grain growth and subsequent photovoltaic performance was investigated by contact angle measurement, morphological characterization of the surface topography and electrochemical impedance analysis. [ABSTRACT FROM AUTHOR]

Recently, perovskite solar cells (PSCs) basing on quasi-two-dimensional (quasi-2D) perovskites with hydrophobic bulky organic cations have received a lot of interests owing to their superior moisture stability. While quasi-2D perovskites have achieved great success in planar p-i-n PSCs, their application in planar n-i-p devices and the corresponding efficiencies lag far behind. In our work, (FPEA) 2 (MA) 4 Pb 5 I 16 perovskite films with high crystallinity, compact and smooth surface were deposited on electron transport layer with NH 4 SCN as an additive. Formamidinium (FA+) were then incorporated into the FPEA based perovskite films to partially replace methylammonium (MA+), and effects of FA+ on the film's vertical orientation, light absorption capacity, carrier lifetime, defect density and electron mobility were studied. It was found that when molar ratio of FA/MA = 0.5/9.5, the film had the highest vertical orientation, enhanced light absorption, less carrier recombination loss. The obtained (FPEA) 2 (FA 0.05 MA 0.95) 4 Pb 5 I 16 based n-i-p PSCs gave a maximum efficiency of 12.17% under standard illumination, retaining 83% of the initial efficiency after stored in air environment (25–30 °C) with 40 ± 5% RH for 1080 h. The results demonstrate an efficient approach to prepare high-quality quasi-2D perovskite films in a n-i-p structure as well as improved device efficiency and stability. [Display omitted] • Optimize the film quality of quasi-2D perovskites in n-i-p structured PSCs. • The FA+ doping is favour to guide better crystalinity and vertical orientation for quasi-2D perovskites. • The incorporation FA+ helps to suppress charge recombination loss and reduce band gap. • FA+ doped device maintains 83% of the initial PCE after being kept in a humidity of 40% for 1080 h. [ABSTRACT FROM AUTHOR]

Environmentally benign and potentially cost-effective Sb 2 Se 3 solar cells have drawn much attention by continuously achieving new efficiency records. This article reports a compatible strategy to enhance the efficiency of planar n-i-p Sb 2 Se 3 solar cells through Sb 2 Se 3 surface modification and an architecture with oriented 1D van der Waals material, trigonal selenium (t-Se). A seed layer assisted successive close spaced sublimation (CSS) is developed to fabricate highly crystalline Sb 2 Se 3 absorbers. It is found that the Sb 2 Se 3 absorber exhibits a Se-deficient surface and negative surface band bending. Reactive Se is innovatively introduced to compensate the surface Se deficiency and form an (101) oriented 1D t-Se interlayer. The p-type t-Se layer promotes a favored band alignment and band bending at the Sb 2 Se 3 /t-Se interface, and functionally works as a surface passivation and hole transport material, which significantly suppresses interface recombination and enhances carrier extraction efficiency. An efficiency of 7.45% is obtained in a planar Sb 2 Se 3 solar cell in superstrate n-i-p configuration, which is the highest efficiency for planar Sb 2 Se 3 solar cells prepared by CSS. The all-inorganic Sb 2 Se 3 solar cell with t-Se shows superb stability, retaining ≈98% of the initial efficiency after 40 days storage in open air without encapsulation., Competing Interests: The authors declare no conflict of interest., (© 2020 The Authors. Published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.)