High-Performance Rigid and Flexible Perovskite Solar Cells with Low-Temperature Solution-Processable Binary Metal Oxide Hole-Transporting Materials

Study on the enhancement of device performance by the action of carbonohydrazide at the buried bottom interface of inverted mesoporous perovskite solar cells

Due to the advantages of low interface resistance, high work function, and high stability, PACz family materials have developed rapidly in p-i-n structure perovskite solar cells (PSCs) in recent years. Numerous studies have shown that PSCs prepared on the basis of PACz family materials or their derivatives as hole transport layers (HTLs) generally exhibit superior performance compared to PSCs prepared on the basis of organic HTL PTAA and inorganic HTL NiOx, especially in terms of stability, demonstrating unparalleled charm. Since the application of PACz-like molecule V1036 as a HTL in PSCs in 2018, research reports on high-performance PSCs based on the PACz family HTL have been widely disseminated. Currently, PSCs based on the PACz HTL exhibit a world record value of 26.7% power conversion efficiency (PCE), breaking the long-standing world record held by n-i-p-structured PSCs, indicating its great potential for application in PSCs. The main problem with using PACz as a HTL is that it exhibits poor wettability toward perovskite precursor solutions, is sensitive to the thickness of the HTL and the roughness of the substrate, has poor thermal stability, and lacks preparation methods, making it difficult to achieve large-area device fabrication. This review summarizes the outstanding achievements of PACz to date, describes the mechanism and unique properties of PACz in PSCs, and looks forward to the future development prospects of PACz.

Influence of Charge Transport Layers on Capacitance Measured in Halide Perovskite Solar Cells

Optimizing band gap, electron affinity, & carrier mobility for improved performance of formamidinium lead tri-iodide perovskite solar cells

Device optimization of CsPbI2Br-based inorganic perovskite solar cells using different charge transport layers via SCAPS-1D

Exploring the performance of perovskite solar cells with dual hole transport layers via SCAPS-1D simulation

Research in solar cells is needed to maximize Indonesia’s vast solar potential that can reach up to 207.898 MW with an average radiation of 4.8 kWh/m2/day. Organometallic perovskite solar cells (PSCs) have gained immense attention due to their rapid increase in efficiency and compatibility with low-cost fabrication methods. Understanding the role of hole transport layer is very important to obtain highly efficient PSCs. In this work, we studied the effect of Hole Transport Layer (HTL) to the performance of perovskite solar cell. The devices with HTL exhibit substantial increase in power conversion efficiency, open circuit voltage and short circuit current compared to the device without HTL. The best performing device is PSC with CuSCN as HTL layer, namely Voc of 0.24, Isc of 1.79 mA, 0.27 FF and efficiency of 0.09%.

The photovoltaic performance of perovskite solar cells with inverted structure depends on the conductivity of the hole transport layer and the charge transport rate to some extent. To further enhance the effect of the hole transport layer, lithium fluoride (LiF) was doped into poly (3,4-ethylene dioxythiophene)-polystyrene sulfonic acid (PEDOT: PSS) to improve its rate of conductivity and interfacial charge transport. The optimal photoelectric conversion efficiency of LiF-based perovskite solar cells that dope hole transport layer is 20.32% with negligible hysteresis, which is much higher than that of the control group (16.70%). Among all photovoltaic parameters, the improvement of open circuit voltage and fill factor is significant. LiF can not only promote the electrical characteristics of PEDOT: PSS and its hole mobility, but also optimize the quality of the upper perovskite film. Perovskite film shows a crystal orientation more conducive to hole transport on the modified hole transport layer, which obtains a dense and smooth absorption layer film. In this study, PEDOT: PSS-based perovskite solar cells with inverted structure doped with LiF are prepared, which provides a simple and effective method to commercialize perovskite solar cells.

Modifying perovskite surface using various organic ammonium halide cations has proven to be an effective approach for enhancing the overall performance of perovskite solar cells. Nevertheless, the impact of the structural symmetry of these ammonium halide cations on perovskite interface termination has remained uncertain. Here, this work investigates the influence of symmetry on the performance of the devices, using molecules based on symmetrical bis(2-chloroethyl)ammonium cation (B(CE)A+) and asymmetrical 2-chloroethylammonium cation (CEA+) as interface layers between the perovskite and hole transport layer. These results reveal that the symmetrical B(CE)A+ cations lead to a more homogeneous surface potential and more comprehensive chelation with uncoordinated Pb2+ compared to the asymmetrical cations, resulting in a more favorable energy band alignment and strengthened defect healing. This strategy, leveraging the spatial geometrical symmetry of the interface cations, promotes hole carrier extraction between functional layers and reduces nonradiative recombination on the perovskite surface. Consequently, perovskite solar cells processed with the symmetrical B(CE)A+ cations achieve a power conversion efficiency (PCE) of 25.60% and retain ≈91% of their initial PCE after 500 h of maximum power point operation. This work highlights the significant benefits of utilizing structurally symmetrical cations in promoting the performance and stability of perovskite solar cells.

This paper presents the effect of a composite poly(3,4-ethylenedioxythiophene) polystyrene sulfonate PEDOT:PSS and copper-doped nickel oxide (Cu:NiOx) hole transport layer (HTL) on the performance of perovskite solar cells (PSCs). Thin films of Cu:NiOx were spin-coated onto fluorine-doped tin oxide (FTO) glass substrates using a blend of nickel acetate tetrahydrate, 2-methoxyethanol and monoethanolamine (MEA) and copper acetate monohydrate. The prepared solution was stirred at 65 °C for 4 h and spin-coated onto the FTO substrates at 3000 rpm for 30 s in a nitrogen glovebox. The Cu:NiOx/FTO/glass structure was then annealed in air at 400 °C for 30 min. A mixture of PEDOT:PSS and isopropyl alcohol (IPA) (in 1:0.05 wt%) was spun onto the Cu:NiOx/FTO/glass substrate at 4000 rpm for 60 s. The multilayer structure was annealed at 130 °C for 15 min. Subsequently, the perovskite precursor (0.95 M) of methylammonium iodide (MAI) to lead acetate trihydrate (Pb(OAc)2·3H2O) was spin-coated at 4000 rpm for 200 s and thermally annealed at 80 °C for 12 min. The inverted planar perovskite solar cells were then fabricated by the deposition of a photoactive layer (CH3NH3PbI3), [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and a Ag electrode. The mechanical behavior of the device during the fabrication of the Cu:NiOx HTL was modeled with finite element simulations using Abaqus/Complete Abaqus Environment CAE. The results show that incorporating Cu:NiOx into the PSC device improves its density–voltage (J–V) behavior, giving an enhanced photoconversion efficiency (PCE) of ~12.8% from ~9.8% and ~11.5% when PEDOT:PSS-only and Cu:NiOx-only are fabricated, respectively. The short circuit current density Jsc for the 0.1 M Cu:NiOx and 0.2 M Cu:NiOx-based devices increased by 18% and 9%, respectively, due to the increase in the electrical conductivity of the Cu:NiOx which provides room for more charges to be extracted out of the absorber layer. The increases in the PCEs were due to the copper-doped nickel oxide blend with the PEDOT:PSS which enhanced the exciton density and charge transport efficiency leading to higher electrical conductivity. The results indicate that the devices with the copper-doped nickel oxide hole transport layer (HTL) are slower to degrade compared with the PEDOT:PSS-only-based HTL. The finite element analyses show that the Cu:NiOx layer would not extensively deform the device, leading to improved stability and enhanced performance. The implications of the results are discussed for the design of low-temperature solution-processed PSCs with copper-doped nickel oxide composite HTLs.

Improving the interface characteristics between the hole-transport layer (HTL) and perovskite absorber layer is crucial for achieving maximum efficiency in inverted perovskite solar cells (PSCs). This paper presents an effective functional compensation layer (FCL) composed of benzothiophene derivatives, particularly 5-(trifluoromethyl)-1-benzothiophene-2-carboxylic acid (TFMBTA); this layer is introduced between the MeO-2PACz HTL and perovskite absorber layer to improve the interfacial characteristics between them. This FCL improves charge transfer, hole extraction, and perovskite deposition by improving the surface morphology of the HTL and optimizing the energy level alignment. The functional groups of TFMBTA effectively passivate perovskite defects. As a result, the introduction of the TFMBTA FCL markedly reduces non-radiative recombination at the interface between the HTL and perovskite layer. The MeO-2PACz-based PSCs with the FCL demonstrated an impressive peak power conversion efficiency of 23.85%, accompanied by substantially enhanced open-circuit voltage (Voc), fill factor (FF), and long-term stability. Similarly, introducing the TFMBTA FCL between the PEDOT:PSS HTL and the perovskite layer enhanced both the stability and efficiency of PSCs, demonstrating the universality of FCLs across different types of HTLs.

The quality of perovskite films is critical to the performance of perovskite solar cells. However, it is challenging to control the crystallinity and orientation of solution-processed perovskite films. Here, solution-phase van der Waals epitaxy growth of MAPbI3 perovskite films on MoS2 flakes is reported. Under transmission electron microscopy, in-plane coupling between the perovskite and the MoS2 crystal lattices is observed, leading to perovskite films with larger grain size, lower trap density, and preferential growth orientation along (110) normal to the MoS2 surface. In perovskite solar cells, when perovskite active layers are grown on MoS2 flakes coated on hole-transport layers, the power conversion efficiency is substantially enhanced for 15%, relatively, due to the increased crystallinity of the perovskite layer and the improved hole extraction and transfer rate at the interface. This work paves a way for preparing high-performance perovskite solar cells and other optoelectronic devices by introducing 2D materials as interfacial layers.

An essential role is played by the charge selective layers, in particular, the hole transport layer (HTL) in determining the performance of perovskite solar cells (PSCs). HTL contribution is even more substantial in the inverted PSCs (p‐i‐n) as it also affects the crystallization process of the overlayer perovskite deposition. The influence of HTL on inverted PSCs was probed, the role through admittance spectroscopy quantified, and the photovoltaic performance correlation with the microstructure of the perovskite established. By measuring the low‐frequency impedance responses of inverted PSCs, the photo‐induced charge transfer dynamics in the PSCs were deciphered, revealing negative chemical inductor features at low frequencies in the Nyquist plots. The noted additional recombination pathways are attributed to the ionic vacancies in the interfacial states. The PSCs fabricated with poly(triaryl amine) showed a higher open‐circuit voltage, lower recombination, and higher charge carrier lifetime. The chemical inductance behavior was supported through variable temperature frequency‐dependent capacitance measurements.

The performance of perovskite solar cells (PSCs) is strongly governed by device architecture and the optoelectronic properties of constituent materials. In this work, a two-dimensional (2D) finite element method (FEM) simulation is employed to investigate a single-junction PSC incorporating a stacked bilayer perovskite absorber and engineered hole transport layers (HTLs), with the aim of enhancing light harvesting and charge transport.To extend the absorption spectrum, a bilayer absorber composed of MAPbI₃ and MASnI₃ is introduced, leading to an increase in short-circuit current density (Jsc) from 17.5 to 18.34mA/cm2 and an improvement in power conversion efficiency (PCE) from 13.31 to 15.01%. The MASnI3 layer primarily acts as a complementary absorber in the near-infrared region while simultaneously modifying the interfacial band alignment, resulting in reduced non-radiative recombination losses. Furthermore, poly(3-hexylthiophene) (P3HT) and P3HT/graphene (P3HT/Gr) nanocomposites with graphene weight ratios of 1, 3, and 5% are employed as HTLs to improve carrier extraction. The incorporation of graphene enhances charge transport through increased electrical conductivity and percolation-assisted pathways within the HTL. The optimized device with 5% graphene-doped P3HT exhibits an open-circuit voltage (Voc) of 1.025V and a maximum PCE of 17.79%. These results demonstrate that the synergistic integration of a bilayer perovskite absorber and graphene-enhanced HTLs provides an effective strategy for improving PSC performance while maintaining a single-junction device architecture.

Thermally-stable and highly-efficient bi-layered NiOx-based inverted planar perovskite solar cells by employing a p-type organic semiconductor