Low-cost Hole-transporting Materials Research Articles

Microscopic analysis of low but stable perovskite solar cell device performance using electron spin resonance

Perovskite solar cells have attracted much attention as next-generation solar cells. However, a typical hole-transport material, spiro-OMeTAD, has associated difficulties including tedious synthesis and high cost. To overcome these shortcomings, an easily synthesized and low-cost hole-transport material has been developed: HND-2NOMe. Although HND-2NOMe has high local charge mobility because of the quasi-planar structure, its lower device performance is a weak point, the cause of which has not yet been clarified. Here, we analyse the source of the lower performance by clarifying the internal states from a microscopic viewpoint using electron spin resonance. We observe hole diffusion from perovskite to HND-2NOMe under dark conditions, indicating hole barrier formation at the perovskite/HND-2NOMe interface, leading to lower performance. Although such a barrier is formed, less hole accumulation for the HND-2NOMe-based cells under solar irradiation occurs, which is related to the stable performance. The sources of the lower but stable performance are crucially important for providing guidelines for improving the device performance.

Dibenzothiophene S, S-Dioxide-Containing Dipolar Molecules As Efficient Hole-Transport Materials for p-i-n Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells (OIH-PSCs) have developed rapidly in the past decade, and the commercialization of OIH-PSCs demands low-cost hole-transport materials (HTMs) with high performance and stability. The present study synthesized two organic HTMs containing dibenzothiophene S-dioxide as the acceptor unit and triphenylamine as the donor (denoted by TPAF-SO2 and TPA-SO2). In TPAF-SO2, the methoxy group and adjacent fluorine atom were introduced to decrease the highest occupied molecular orbital energy level. In TPA-SO2, the methyl sulfide group is the end group that can passivate the lead ion. TPAF-SO2 and TPA-SO2 exhibit hole-transport mobilities as high as 1.12 × 10-3 and 2.31 × 10-3 cm2 v-1 s-1, respectively, and strongly passivate Pb vacancies. Compared with TPAF-SO2, TPA-SO2 is more suitable for the growth of perovskite crystals. The perovskite grown on the latter has a lower trap density and higher carrier mobility; thus, both the nonradiative recombination and the charge-transport loss are decreased. The OIH-PSC based on TPA-SO2 as the HTM achieved a power conversion efficiency (PCE) as high as 22.08%, whereas the device based on TPAF-SO2 achieved a PCE of only 18.42%. In addition, the unencapsulated device based on TPA-SO2 can maintain 85% of the initial PCE after being stored in N2 for 1200 h, whereas the device based on TPAF-SO2 decayed rapidly to zero in 800 h under the same conditions.

Fluorinated hole transport material resistant to high annealing temperature applied in inverted perovskites solar cells

A dopant-free and low-cost hole transport material (HTM) with dibenzo[b,d]thiophene as the center unit, bis(4-methoxyphenyl)amine as the terminal unit, and fluorine substitution adjacent to the methoxyl (named DBT-4F-MOP) is designed and applied in inverted organic-inorganic hybrid perovskite solar cells (OIH-PSCs). The synthetic cost of DBT-4F-MOP in the lab is just as low as 115 CNY/g, which is much lower than the benchmark HTM poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA, 2500 CNY/g). Due to the introduction of the fluorine atoms, the annealing temperature of the HTM can be increased by over 150 ℃. The highest efficiency of the inverted device based on it can reach 16.8 %, with an open circuit voltage of 1.04 V, a short circuit current of 21.57 mA cm−2, and a fill factor of 74.69 %, while the reference device based on PTAA can reach a PCE of 17.54 %. This work provides an avenue for the design of low-cost, dopant-free, and high-annealing temperature HTMs for inverted OIH-PSCs.

Cooperating with additives: low-cost hole-transporting materials for improved stability of perovskite solar cells

The widespread adoption of perovskite-based solar technologies is strictly related to the cost reduction of the hole-transporting component in the device, while maintaining compatibility with its absorbing active layer. To...

Improving the Conductivity of Amide-Based Small Molecules through Enhanced Molecular Packing and Their Application as Hole Transport Mediators in Perovskite Solar Cells.

Organic-inorganic hybrid halide perovskite solar cells (PSCs) have attracted substantial attention from the photovoltaic research community, with the power conversion efficiency (PCE) already exceeding 26%. Current state-of-the-art devices rely on Spiro-OMeTAD as the hole-transporting material (HTM); however, Spiro-OMeTAD is costly due to its complicated synthesis and expensive product purification, while its low conductivity ultimately limits the achievable device efficiency. In this work, we build upon our recently introduced family of low-cost amide-based small molecules and introduce a molecule (termed TPABT) that results in high conductivity values (∼10-5 S cm-1 upon addition of standard ionic additives), outperforming our previous amide-based material (EDOT-Amide-TPA, ∼10-6 S cm-1) while only costing an estimated $5/g. We ascribe the increased optoelectronic properties to favorable molecular packing, as shown by single-crystal X-ray diffraction, which results in close spacing between the triphenylamine blocks. This, in turn, results in a short hole-hopping distance between molecules and therefore good mobility and conductivity. In addition, TPABT exhibits a higher bandgap and is as a result more transparent in the visible range of the solar spectrum, leading to lower parasitic absorption losses than Spiro-OMeTAD, and has increased moisture stability. We applied the molecule in perovskite solar cells and obtained good efficiency values in the ∼15% range. Our approach shows that engineering better molecular packing may be the key to developing high-efficiency, low-cost HTMs for perovskite solar cells.

Simulation and analysis of high-performance hole transport material SrZrS3-based perovskite solar cells with a theoretical efficiency approaching 26%

To process the toxicity and stability issues of hybrid lead halide perovskites, we suggest chalcogenide perovskites as an actual alternative family of material-based solar cells. Zr-based chalcogenides AZrS3 (A = Ba, Ca, or Sr) are the most studied family of chalcogenide perovskites for optoelectronic applications, thanks to their low cost, strong absorbency, and high PCE. A device simulation of SrZrS3 as an absorbing material solar cell, as well as a proposal of low-cost Hole Transport Materials HTMs (Cu2O, CuSCN, and NiOx), were achieved by using the software SCAPS-1D. The key parameters (thickness, doping concentration (NA), and temperature) for each configuration are varied to inspect their impact on the device’s performance. In the interest of replacing the highly expensive gold (Au) electrode, the functionality of the metal work function was also investigated. As a result, we have found that for SrZrS3, the optimized configuration is: Ni (metal back contact)/NiOx (HTM)/SrZrS3 (Absorber)/ZnO (ETM)/FTO, which delivered at 400 K: a PCE of 25.97%, a VOC of 1.18 V, a JSC of 26.13 mA/cm2 and an FF of 84.29%.

Dithieno[3,2-a:2′,3′-c]phenazine based hole-transporting materials for efficient perovskite solar cells: Effects of donors numbers

Incorporation of electron-deficient polycyclic aromatics into molecular skeleton has been proved to be an effective strategy for improving the device performance of organic photovoltaics. In this context, three low-cost hole-transporting materials (HTMs) endowed with dithieno[3,2-a:2′,3′-c]phenazine core were successfully synthesized and employed for perovskite solar cells (PSCs). A comparative evaluation in relation to the numbers of peripheral donors was systematically investigated by measurement of their photophysical, electrochemical and photovoltaic performance. It is revealed that the low-symmetrical WH04 featuring three triphenylamine (TPA) donors exhibited a deeper HOMO level, a higher hole-transporting capacity and smoother film morphology than the molecules with two or four terminal donors. As a result, the WH04-based PSCs realized the highest power conversion efficiency of 20.52%, accompanied with excellent long-term device stability, which is competitive with spiro-OMeTAD based devices. We believe that molecular engineering of donors numbers is envisioned as an effective strategy for constructing highly efficient D-A-D type HTMs for PSCs.

Low-cost star-shaped hole-transporting materials with isotropic properties and its application in perovskite solar cells

The development of new hole-transporting materials (HTMs) with high hole mobility, suitable molecular configuration and low cost is of profound significance for the enhancement of the photovoltaic performance of perovskite solar cells (PSCs) and the advancement of industrialization. In this work, we have designed and synthesized a highly efficient and low-cost HTM of star-shaped carbazole (MPTCZ-FNP), which has isotropic, multi-channel hole transport properties. As the results show, MPTCZ-FNP has suitable energy levels, good hole transport properties, good film formation and hydrophobicity. According to the results, the efficiency of the mesoporous n-i-p structured PSCs prepared using MPTCZ-FNP material is up to 20.27%, which is higher than that of the traditional HTM Spiro-OMeTAD of 18.35%. Therefore, the present work has designed and synthesized a three-dimensional star-shaped HTM, which provides a reference for the design of subsequent highly efficient HTMs.

Recent Advances in Zinc Anc Cooper Phthalocyanines As Hole Transporting Materials in Perovskite Solar Cells

Recently, significant progresses have been achieved in the fabrication of highly efficient perovskite solar cells, while major challenges, such as commercial viablity of exotic materials and their instability, remain as an obstacle. Hole transporting materials (HTMs) represent a tricky choice for the fabrication of efficient solar cells and the cost uneffective Spiro-OMeTAD continue to be so far the most obvious candidate. Semiconductors molecules, such as metallophthalocyanines (MPcs)1 appeared as a promising class of p-type material, since they are less expensive and more stable.In this communication, we will present the synthesis of novel ZnPcs,2 ZnPc dimers3 and CuPcs4 (see as examples Figure 1) as efficient, stable, and low cost HTMs in PSCs. The MPcs are substituted with functional groups that possesses a very good solubility in a wide range of organic solvents, adequate HOMO LUMO levels and thus can be applied from solution processing in a wide range of perovskite solar cell devices.Figure 1. Different ZnPcs structures as HTMs in PSCs References M. Urbani, M. E. Ragoussi, M. K. Nazeeruddin, T. Torres, Coord. Chem. Rev. 2019, 381, 1-64. P. Huang, A. Hernández, S. Kazim, J. Ortíz, Á. Sastre-Santos, S. Ahmad Sustainable Energy &Fuels. 2020, 4, 6188-6195. a) D. Molina, M. A. Ruiz-Preciado, F. Sadegh, M. João Álvaro-Martins, M. Grätzel, A. Hagfeldt, Á. Sastre-Santos, J. Porphyr. Phthalocyanines, 2019, 23, 546–553. b) D. Molina, M. A. Ruiz‐Preciado, B. Carlsen, F. T. Eickemeyer, B. Yang, N. Flores‐Díaz, M. J. Álvaro‐Martins, K. Nonomura, A. Hagfeldt and Á. Sastre‐Santos, ChemPhotoChem, 2020, 4, 307–314. a) L. Caliò, J. Follana-Berná, S. Kazim, M. Madsen, H. G. Rubahn, Á. Sastre-Santos, S. Ahmad, Sustainable Energy Fuels, 2017, 1, 2071-2077. b) P. Huang, A. Hernández, J. Follana-Berná, S. Kazim, J. Ortíz, Á. Sastre-Santos, S. Ahmad, ACS Appl. Energy Mater. 2021, 4, 9, 10124–10135 Figure 1

Oxidative polymerization of triarylamines: a promising route to low-cost hole transport materials for efficient perovskite solar cells

Efficient and economic oxidative polymerization enables the synthesis of polytriarylamines (PTAAs), which show comparable performances to high-cost commercial PTAAs in perovskite solar cells delivering efficiencies of 18–20%.

Stable Perovskite Solar Cells Using Molecularly Engineered Functionalized Oligothiophenes as Low-Cost Hole-Transporting Materials.

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.

Recent Advances in Zinc Anc Cooper Phthalocyanines As Hole Transporting Materials in Perovskite Solar Cells

Recently, significant progresses have been achieved in the fabrication of highly efficient perovskite solar cells, while major challenges, such as commercial viablity of exotic materials and their instability, remain as an obstacle. Hole transporting materials (HTMs) represent a tricky choice for the fabrication of efficient solar cells and the cost uneffective Spiro-OMeTAD continue to be so far the most obvious candidate. Semiconductors molecules, such as metallophthalocyanines (MPcs)1 appeared as a promising class of p-type material, since they are less expensive and more stable.In this communication, we will present the synthesis of novel ZnPcs,2 ZnPc dimers3 and CuPcs4 (see as examples Figure 1) as efficient, stable, and low cost HTMs in PSCs. The MPcs are substituted with functional groups that possesses a very good solubility in a wide range of organic solvents, adequate HOMO LUMO levels and thus can be applied from solution processing in a wide range of perovskite solar cell devices.Figure 1. Different ZnPcs structures as HTMs in PSCs References M. Urbani, M. E. Ragoussi, M. K. Nazeeruddin, T. Torres, Coord. Chem. Rev. 2019, 381, 1-64. P. Huang, A. Hernández, S. Kazim, J. Ortíz, Á. Sastre-Santos, S. Ahmad Sustainable Energy &Fuels. 2020, 4, 6188-6195. a) D. Molina, M. A. Ruiz-Preciado, F. Sadegh, M. João Álvaro-Martins, M. Grätzel, A. Hagfeldt, Á. Sastre-Santos, J. Porphyr. Phthalocyanines, 2019, 23, 546–553. b) D. Molina, M. A. Ruiz‐Preciado, B. Carlsen, F. T. Eickemeyer, B. Yang, N. Flores‐Díaz, M. J. Álvaro‐Martins, K. Nonomura, A. Hagfeldt and Á. Sastre‐Santos, ChemPhotoChem, 2020, 4, 307–314. a) L. Caliò, J. Follana-Berná, S. Kazim, M. Madsen, H. G. Rubahn, Á. Sastre-Santos, S. Ahmad, Sustainable Energy Fuels, 2017, 1, 2071-2077. b) P. Huang, A. Hernández, J. Follana-Berná, S. Kazim, J. Ortíz, Á. Sastre-Santos, S. Ahmad, submitted.

Low-Cost Hole-Transporting Materials Based on Carbohelicene for High-Performance Perovskite Solar Cells.

Two hole-transporting materials (HTMs) based on carbohelicene cores, CH1 and CH2, are developed and used in fabricating efficient and stable perovskite solar cells (PSCs). Owing to the rigid conformation of the helicene core, both compounds possess unique CH-π interactions in the crystalline packing pattern and good phase stability, which are distinct from the π-π intermolecular interactions of conventional planar and spiro-type molecules. PSCs based on CH1 and CH2 as HTMs deliver excellent device efficiencies of 19.36 and 18.71%, respectively, outperforming the control device fabricated with spiro-OMeTAD (18.45%). Furthermore, both PSCs exhibit better ambient stability, with 90% of initial performance retained after aging with a 50-60% relative humidity at 25 °C for 500 h. Due to the low production cost of both compounds, these newly designed carbohelicene-type HTMs have the potential for the future commercialization of PSCs.

Low-cost molecular glass hole transport material for perovskite solar cells

The availability of low-cost hole transport materials (HTMs) that are easy to process is crucial for the eventual commercialization of perovskite solar cells (PSCs), as the commonly used HTM (Spiro-OmeTAD) is expensive, and its processing is complex. In this study, we synthesized an amorphous molecular material (termed as TPA-glass) from the condensation of 2-mexylamino-4-methylamino-6-(4-aminophenylamino)-1,3,5-triazine and N-(4-formylphenyl)diphenylamine with a low-cost and easy process, and applied as an HTM in PSCs. We investigated the effect of TPA-glass thin-films with varying thickness, as well as their corresponding solar cell’s properties. The preliminary performance data indicate that TPA-glass thin-film can be a potential HTM candidate for planar PSCs.

Deciphering the effect of replacing thiophene with selenophene in diketopyrrolopyrrole (DPP)-based low cost hole transport materials on the performance of perovskite solar cells

Diketopyrrolopyrrole (DPP)-based low-cost hole-transporting materials are designed via facile approaches for efficient perovskite solar cells, which endowed impressive PCE over 16% along with ambient stability.

Teaching an Old Anchoring Group New Tricks: Enabling Low-Cost, Eco-Friendly Hole-Transporting Materials for Efficient and Stable Perovskite Solar Cells.

As a key component in perovskite solar cells (PVSCs), hole-transporting materials (HTMs) have been extensively explored and studied. Aiming to meet the requirements for future commercialization of PVSCs, HTMs which can enable excellent device performance with low cost and eco-friendly processability are urgently needed but rarely reported. In this work, a traditional anchoring group (2-cyanoacrylic acid) widely used in molecules for dye-sensitized solar cells is incorporated into donor-acceptor-type HTMs to afford MPA-BT-CA, which enables effective regulation of the frontier molecular orbital energy levels, interfacial modification of an ITO electrode, efficient defect passivation toward the perovskite layer, and more importantly alcohol solubility. Consequently, inverted PVSCs with this low-cost HTM exhibit excellent device performance with a remarkable power conversion efficiency (PCE) of 21.24% and good long-term stability in ambient conditions. More encouragingly, when processing MPA-BT-CA films with the green solvent ethanol, the corresponding PVSCs also deliver a substantial PCE as high as 20.52% with negligible hysteresis. Such molecular design of anchoring group-based materials represents great progress for developing efficient HTMs which combine the advantages of low cost, eco-friendly processability, and high performance. We believe that such design strategy will pave a new path for the exploration of highly efficient HTMs applicable to commercialization of PVSCs.

Carbazole-Based Spiro[fluorene-9,9'-xanthene] as an Efficient Hole-Transporting Material for Perovskite Solar Cells.

For the practical application of perovskite solar cells (PSC), it is desirable to have high efficiency, long-term stability, and low manufacturing cost. Therefore, it is required to develop inexpensive and well-performing hole-transporting materials (HTMs). In this study, we synthesized SFXDAnCBZ, which is a new carbazole-based spiro[fluorene-9,9'-xanthene] (SFX) derivative, where the central core and end-cap units consist of SFX and N3,N6-bis(di-4-anisylamino)-9H-carbazole (DAnCBZ), respectively, as an efficient and low-cost HTM for PSCs. Photoluminescence quenching at the SFXDAnCBZ/perovskite interface was more effective than at the perovskite/Spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxy-phenyl-amine) 9,9'spiro-bifluorene) interface. We fabricated a PSC with a power conversion efficiency (PCE) of 20.87% under 1 sun illumination (100 mW cm-2) using SFXDAnCBZ as an HTM. This value is comparable to that measured for the benchmark Spiro-OMeTAD. Thus, this result confirms that SFX core-based materials can be a new kind of HTMs for high-efficiency and low-cost PSCs.

In-Situ Electropolymerized Polyamines as Dopant-Free Hole-Transporting Materials for Efficient and Stable Inverted Perovskite Solar Cells

Currently, there is an urgent need to develop low-cost hole-transporting materials (HTMs) for inverted perovskite solar cells (PSCs), whose power conversion efficiency (PCE) is still inferior to th...

High-efficiency planar p-i-n perovskite solar cells based on dopant-free dibenzo[b,d]furan-centred linear hole transporting material

To implement the commercialization of perovskite solar cells (pero-SCs) in the future, employing high-efficiency and low-cost hole-transporting materials (HTMs) is one of crucial factors. Herein, through investigating the electronic structure and geometry of the molecular structure with density functional theory calculation, a dibenzo[b,d]furan-centred molecular hole-transporting material (termed DBFMT) is synthesized from commercial monomers with a relatively low cost of approximately US$35 per gram in laboratory. This dopant-free HTM is applied in the planar p-i-n pero-SCs with a structure of ITO/DBFMT/perovskite (MAPbI3)/C60/BCP/Ag. Based on the different concentration of DBFMT, the corresponding top perovskite grain sizes are different. After optimization, the power conversion efficiency (PCE) reaches as high as 20.51%, with a short-circuit current density of 23.70 mA cm−2, an open circuit voltage of 1.07 V, and a fill factor of 80.48%. As far as we know, the PCE of 20.51% is among the highest efficiency for the p-i-n pero-SCs based on the dopant-free HTMs.

Characteristics of Large Area Perovskite Solar Cells from Electrodes of Used Car Batteries

Power conversion efficiency (PCE) of perovskite solar cells increases very rapidly and more than 22% is already achieved. However, some problems still need to be resolved for mass production and commercialization, including reducing production costs and development of large area solar cells. The best PCE is reached by very small active area, mostly below 0.5 cm2 which is mostly produced by spin-coating technique. Moreover, the perovskite precursor materials, mostly lead (II) iodide (PbI2) and hole-transport materials (HTM) Spiro-OMeTAD are expensive material in perovskite solar cells. Therefore, the use of low-cost perovskite precursors and low-cost HTM materials is one way to reduce the whole production costs of perovskite solar cells. Nowadays, many groups have been developed HTM-free perovskite solar cells using carbon-based mesoscopic solar cells for low cost production and large area perovskite solar cells, although the PCE of large area perovskite solar cells is still half than that very small area prepared by spin-coating technique. Here, we report our recent study to fabricate perovskite solar cells using mesoscopic carbon-based structure consisting of glass/ITO/TiO2/ZrO2/perovskite/carbon with active area larger than 1 cm2 by use of simple screen printing technique in ambient air with high humidity. We also synthesize PbI2 as perovskite precursor material from electrodes of used car battery to reduce the cost of solar cells production. Although, the PCE is still much lower than that reported by other groups, however, our study shows that perovskite solar cells from used car battery and with active area more than 1 cm2 can be fabricated in ambient air with high humidity by use of simple screen printing technique.