Phosphine Oxide Derivative as a Passivating Agent to Enhance the Performance of Perovskite Solar Cells

Defects of metal-halide perovskites detrimentally influence the optoelectronic properties of the thin film and, ultimately, the photovoltaic performance of perovskite solar cells (PSCs). Especially, defect-mediated nonradiative recombination that occurs at the perovskite interface significantly limits the power conversion efficiency (PCE) of PSCs. In this regard, interfacial engineering or surface treatment of perovskites has become a viable strategy for reducing the density of surface defects, thereby improving the PCE of PSCs. Here, an organic molecule, tris(5-((tetrahydro-2H-pyran-2-yl)oxy)pentyl)phosphine oxide (THPPO), is synthesized and introduced as a defect passivation agent in PSCs. The P=O terminal group of THPPO, a Lewis base, can passivate perovskite surface defects such as undercoordinated Pb2+. Consequently, improvement of PCEs from 19.87 to 20.70% and from 5.84 to 13.31% are achieved in n−i−p PSCs and hole-transporting layer (HTL)-free PSCs, respectively

Efficiency vs. stability: dopant-free hole transporting materials towards stabilized perovskite solar cells

In the last decade, perovskite solar cells have been considered a promising and burgeoning technology for solar energy conversion with a power conversion efficiency currently exceeding 24%. However, although perovskite solar cells have achieved high power conversion efficiency, there are still several challenges limiting their industrial realization. The actual bottleneck for real uptake in the market still remains the cost-ineffective components and instability, to which doping-induced degradation of charge selective layers may contribute significantly. This article overviews the highest performance molecular and polymeric doped and dopant-free HTMs, showing how small changes in the molecular structure such as different atoms and different functional groups and changes in substitution positions or the length of the pi-conjugated systems can affect photovoltaic performance and long-term stability of perovskite solar cells

Synthesis of N-Bridged Pyrido[4,3-d]pyrimidines and Self-Assembly into Twin Rosette Cages and Nanotubes in Organic Media

Abstract Two N-bridged pyrido[4,3-d]pyrimidine derivatives were synthesized toward realization of a self-assembled bis-rosette cage, in organic media. Starting from commercially available malononitrile dimer and dimethyl 5-aminoisophthalate, the target molecules were synthesized in 11 steps using a convergent approach. The final bridged compounds were characterized by nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. The hierarchical self-assembly of the nanocages into rosette nanotubes and nanobundles was established by electron microscopy and molecular modelling studies

C60 Thin Films in Perovskite Solar Cells: Efficient or Limiting Charge Transport Layer?

In this work, we identify the importance of C60 and compact-TiO2 (cTiO2) as electron transport layers on the device performance of coevaporated n–i–p perovskite solar cells. We found (1) a synergetic effect between both layers when extracting the charges and (2) that optimization of the C60 layer is essential for obtaining devices with enhanced device performance. In particular, we found that a C60 layer of an optimum thickness (20 nm), an additional charge transport resistance is observed by impedance analysis, indicating that devices with nonoptimized C60 thickness could limit the fabrication of highly efficient perovskite solar cells.N.K., C.M., A.O.A., and F.F.-S. thank the European Union′s Horizon 2020 research nos. 764787 and 763977. H.K. acknowledges the support of the H2020 program for Solar-ERANET funding of the BOBTANDEM (2019-2022) A.A.S. and C.I. acknowledge the Swiss National Science Foundation (SNSF) funding through Synergia Grant EPISODE (grant no. CRSII5_171000). The authors thank the project German Research Foundation (DFG) (Projekt number 424101351)–Swiss National Foundation (SNF) (200021E_186390). A.O.A. and F.F.-S. acknowledge Ministerio de Economía y Competitividad (MINECO) from Spain under the project ENE2017-85087-C3-1-R and Generalitat Valenciana under the project PROMETEO/2020/028 for financial support

Light Stability Enhancement of Perovskite Solar Cells Using 1H,1H,2H,2H-Perfluorooctyltriethoxysilane Passivation

Passivation approaches of perovskite surface are key to improve the light stability of perovskite solar cells. However, a passivation strategy is still required to enhance the durability of the perovskite layer. Here, a promising passivation concept is demonstrated by applying a fluorinated agent on the perovskite layer for light stability improvement. Such fluorinated passivation agents can prevent the formation of Pb-0 at the perovskite surface resulting in suppressing a defect-induced recombination and improving the durability of the perovskite solar cells. As an additional benefit, the fluorinated passivation agent increases the V-OC which improves the photovoltaic performance of the perovskite solar cells. Consequently, with a fluorinated passivation agent, the perovskite maintains a power conversion efficiency of 95% after 300 h of light illumination. It is found that the fluorinated passivation material of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) can improve the stability of the perovskite solar cells

Cut from the Same Cloth: Enamine-Derived Spirobifluorenes as Hole Transporters for Perovskite Solar Cells

To attain commercial viability, perovskite solar cells (PSCs) have to be reasonably priced, highly efficient, and stable for a long period of time. Although a new record of a certified power conversion efficiency (PCE) value over 25% was achieved, PSC performance is limited by the lack of hole-transporting materials (HTMs), which extract positive charges from the light-absorbing perovskite layer and carry them to the electrode. Here, we report spirobifluorene-based HTMs with finely tuned energy levels, high glass-transition temperature, and excellent charge mobility and conductivity enabled by molecularly engineered enamine arms. HTMs are synthesized using simple condensation chemistry, which does not require costly catalysts, inert reaction conditions, and time-consuming product purification procedures. Enamine-derived HTMs allow the fabrication of PSCs reaching a maximum PCE of 19.2% and stability comparable to spiro-OMeTAD. This work demonstrates that simple enamine condensation reactions could be used as a universal path to obtain HTMs for highly efficient and stable PSCs

Dopant-free hole transport materials afford efficient and stable inorganic perovskite solar cells and modules

The emerging CsPbI3 perovskites are highly efficient and thermally stable materials for wide-bandgap perovskite solar cells (PSCs), but the doped hole transport materials (HTMs) accelerate the undesirable phase transition of CsPbI3 in ambient. Herein, a dopant-free D-π-A type HTM named CI-TTIN-2F has been developed which overcomes this problem. The suitable optoelectronic properties and energy-level alignment endow CI-TTIN-2F with excellent charge collection properties. Moreover, CI-TTIN-2F provides multisite defect-healing effects on the defective sites of CsPbI3 surface. Inorganic CsPbI3 PSCs with CI-TTIN-2F HTM feature high efficiencies up to 15.9%, along with 86% efficiency retention after 1000 h under ambient conditions. Inorganic perovskite solar modules were also fabricated that exhibiting an efficiency of 11.0% with a record area of 27 cm2. This work confirms that using efficient dopant-free HTMs is an attractive strategy to stabilize inorganic PSCs for their future scale-up

Zn(II) and Cu(II) tetrakis(diarylamine)phthalocyanines as hole-transporting materials for perovskite solar cells

Finding new hole-transporting materials (HTMs) suitable for replacing the state-of-the-art spiro-OMe-TAD is still challenging. In this work, newly synthesized diarylamine-substituted metal phthalocyanines (MPcs, M 1/4 Zn(II) or Cu(II)) functionalized with either linear or branched alkoxy chains are evaluated as HTMs in perovskite solar cells. Both the nature of the alkoxy chains and that of the coordinated metal species were found to influence the functional properties of the new MPcs. In particular, devices based on a ZnPc featuring four n-butoxy side chains exhibited the highest power conversion efficiencies (PCEs). A PCE of 20.00% was reached for triple cation perovskite devices, and a PCE up to 20.18% could be achieved for double cation devices. (C) 2022 The Authors. Published by Elsevier Ltd