RESUMEN
Naphthalene diimides (NDI) are widely serving as the skeleton to construct electron transport materials (ETMs) for optoelectronic devices. However, most of the reported NDI-based ETMs suffer from poor interfaces with the perovskite which deteriorates the carrier extraction and device stability. Here, a representative design concept for editing the peripheral groups of NDI molecules to achieve multifunctional properties is introduced. The resulting molecule 2,7-bis(2,2,3,3,4,4,4-heptafluorobutyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (NDI-C4F) incorporated with hydrophobic fluorine units contributes to the prevention of excessive molecular aggregation, the improvement of surface wettability and the formation of strong chemical coordination with perovskite precursors. All these features favor retarding the perovskite crystallization and achieving superior buried interfaces, which subsequently promote charge collection and improve the structural compatibility between perovskite and ETMs. The corresponding PSCs based on low-temperature processed NDI-C4F yield a record efficiency of 23.21%, which is the highest reported value for organic ETMs in n-i-p PSCs. More encouragingly, the unencapsulated devices with NDI-C4F demonstrate extraordinary stability by retaining over 90% of their initial PCEs after 2600 h in air. This work provides an alternative molecular strategy to engineer the buried interfaces and can trigger further development of organic ETMs toward reliable PSCs.
RESUMEN
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.
RESUMEN
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.
RESUMEN
Power conversion efficiency (PCE) and long-term stability are two vital issues for perovskite solar cells (PSCs). However, there is still a lack of suitable hole transport layers (HTLs) to endow PSCs with both high efficiency and stability. Here, NiOx nanoparticles are promoted as an efficient and 85 °C/85%-stable inorganic HTL for high-performance n-i-p PSCs, with the introduction of perovskite quantum dots (QDs) between perovskite and NiOx as systematic interfacial engineering. The QD intercalation enhances film morphology and assembly regulation of NiOx HTLs . Due to structure-function correlations, hole mobility within NiOx HTL is improved. And the hole extraction from perovskite to NiOx is also facilitated, resulting from reduced trap states and optimized energy level alignments. Hence, the promoted NiOx -based n-i-p PSCs exhibit high PCE (21.59%) and excellent stability (sustaining 85 °C aging in air without encapsulation). Furthermore, encapsulated solar modules with QDs-promoted NiOx HTLs show impressive stability during 85 °C/85% aging test for 1000 hours. With high transparency, QDs-promoted NiOx is also demonstrated to be an advanced HTL for semitransparent PSCs. This work develops promising NiOx inorganic HTL in n-i-p PSCs for manufacturing next-generation photovoltaic devices.
RESUMEN
Triarylamine-substituted bithiophene (BT-4D), terthiophene (TT-4D), and quarterthiophene (QT-4D) small molecules are synthesized and used as low-cost hole-transporting materials (HTMs) for perovskite solar cells (PSCs). The optoelectronic, electrochemical, and thermal properties of the compounds are investigated systematically. The BT-4D, TT-4D, and QT-4D compounds exhibit thermal decomposition temperature over 400 °C. The n-i-p configured perovskite solar cells (PSCs) fabricated with BT-4D as HTM show the maximum power conversion efficiency (PCE) of 19.34% owing to its better hole-extracting properties and film formation compared to TT-4D and QT-4D, which exhibit PCE of 17% and 16%, respectively. Importantly, PSCs using BT-4D demonstrate exceptional stability by retaining 98% of its initial PCE after 1186 h of continuous 1 sun illumination. The remarkable long-term stability and facile synthetic procedure of BT-4D show a great promise for efficient, stable, and low-cost HTMs for PSCs for commercial applications.
RESUMEN
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.
RESUMEN
Nanocrystalline hydrogenated silicon (nc-Si:H) substrate configuration n-i-p solar cells have been fabricated on soda lime glass substrates with active absorber layers prepared by plasma enhanced chemical vapor deposition (PECVD) and radio frequency magnetron sputtering. The cells with nanocrystalline PECVD absorbers and an untextured back reflector serve as a baseline for comparison and have power conversion efficiency near 6%. By comparison, cells with sputtered absorbers achieved efficiencies of about 1%. Simulations of external quantum efficiency (EQE) are compared to experimental EQE to determine a carrier collection probability gradient with depth for the device with the sputtered i-layer absorber. This incomplete collection of carriers generated in the absorber is most pronounced in material near the n/i interface and is attributed to breaking vacuum between deposition of layers for the sputtered absorbers, possible low electronic quality of the nc-Si:H sputtered absorber, and damage at the n/i interface by over-deposition of the sputtered i-layer during device fabrication.
RESUMEN
The fabrication of perovskite solar cells in an N-I-P structure with compact titanium dioxide blocking, mesoporous titanium dioxide scaffold, single-step perovskite and hole-transport layers deposited using the slot-die coating technique is reported. Devices on fluorine-doped tin oxide-coated glass substrates with evaporated gold top contacts and four slot-die-coated layers are demonstrated, and best cells reach stabilized power conversion efficiencies of 7%. This work demonstrates the suitability of slot-die coating for the production of layers within this perovskite solar cell stack and the potential to transfer to large area and roll-to-roll manufacturing processes.
RESUMEN
Optimization of the interface between the electron transport layer (ETL) and the hybrid perovskite is crucial to achieve high-performance perovskite solar cell (PSC) devices. Fullerene-based compounds have attracted attention as modifiers on the surface properties of TiO2, the archetypal ETL in regular n-i-p PSCs. However, the partial solubility of fullerenes in the aprotic solvents used for perovskite deposition hinders its application to low-temperature solution-processed PSCs. In this work, we introduce a new method for fullerene modification of TiO2 layers derived from nanoparticles (NPs) inks. Atomic force microscopy characterization reveals that the resulting ETL is a network of TiO2-NPs interconnected by fullerenes. Interestingly, this surface modification enhances the bottom interface of the perovskite by improving the charge transfer as well as the top perovskite interface by reducing surface trap states enhancing the contact with the p-type buffer layer. As a result, rigid PSCs reached a 17.2% power conversion efficiency (PCE), while flexible PSCs exhibited a remarkable stabilized PCE of 12.2% demonstrating the potential application of this approach for further scale-up of PSC devices.