Pyridine-triphenylamine hole transport material for inverted perovskite solar cells

In the light of superior interaction between pyridine unit and perovskite,a facile star-shaped triphenylamine-based hole transport material(HTM)incorporating pyridine core(coded as H-Pyr)is designed and synthesized.A reference HTM with benzene core,coded as H-Ben,is also prepared for a comparative study.The effects of varying core on HTMs are investigated by comparing the photophysical,electrochemical and hole mobility properties.It is found that pyridine core exhibits better conjunction and decreased dihedral angles with triphenylamine side arms than that of benzene,leading to obviously better hole mobility and well-matched work function.The perovskite film prepared on H-Pyr also shows improved crystallization than on H-Ben.Photoluminescence and electrochemical impedance studies indicate improved charge extraction and reduced recombination in the H-Pyr-based perovskite solar cells.Consequently,H-Pyr-based device exhibits higher efficiency than H-Ben-based one.After doping with a Lewis acid,tris(pentafluorophenyl)borane,H-Pyr-based device delivers a champion efficiency of 17.09%,which is much higher compared with 12.14% of the device employing conventional poly(3,4-ethy lenedioxythiophene)polystyrene sulfonate(PEDOT:PSS)as HTM.Moreover,the H-Pyr-based device displays good long-term stability that the power conversion efficiency remains over 80% of the initial value after storage in ambient(relative humidity=50±5%)for 20 days.     

Nickel oxide for inverted structure perovskite solar cells

The emergence of inverted perovskite solar cells(PSCs) has attached great attention derived from the potential in improving stability. Charge transporting layer, especially hole transporting layer is crucial for efficient inverted PSCs. Organic materials were used as hole transporting layer previously. Recently, more and more inorganic hole transporting materials have been deployed for further improving the device stability. Nickel oxide(NiOx) as p-type metal oxide, owning high charge mobility and intrinsic stability,has been widely adopted in inverted PSCs. High performance over 20% efficiency has been achieved on NiOx base inverted PSCs. Herein, we have summarized recent progresses and strategies on the NiOx based PSCs, including the synthesis or deposition methods of NiOx, doping and surface modification of NiOx for efficient and stable PSCs. Finally, we will discuss current challenges of utilizing NiOx HTLs in PSCs and attempt to give probable solutions to make further development in efficient as well as stable NiOx based PSCs.     

Copper-copper iodide hybrid nanostructure as hole transport material for efficient and stable inverted perovskite solar cells

A CuI coated Cu hybrid nanostructure by partial iodation of Cu nanowires was used as hole transport material(HTM) to enhance the charge transfer in inverted perovskite solar cells(PSCs). The outer CuI achieved efficient charge extraction, and the inner copper facilitated the extracted charges to be rapidly transferred, further improving the overall cell performance. Furthermore,we employed a mixture of [6,6]-phenyl-C71-butyric acid methyl ester(PCBM) and ZnO nanoparticles as electron transport material(ETM) to achieve the fabrication of stable PSCs. The best efficiency was up to 18.8%. This work represents a fundamental clue for the design of efficient and stable PSCs using the chemical in-situ construction strategy for HTM and integration of PCBM and ZnO as ETM.     

Titanylphthalocyanine as hole transporting material for perovskite solar cells

Titanylphthalocyanine(TiOPc) as hole transporting material(HTM) was successfully synthesized by a simple process with low cost. Perovskite solar cells using the TiOPc as HTM were fabricated and characterized. TiOPc as HTM plays an important role in increasing the power conversion efficiency(PCE) by minimizing recombination losses at the perovskite/Au interface because TiOPc as HTM can extract photogenerated holes from the perovskite and then transport quickly these charges to the back metal electrode. In the research, the β-TiOPc gives a higher PCE than α-TiOPc for the devices due to sufficient transfer dynamics. The β-TiOPc was applied in perovskite solar cells without dopping to afford an impressive PCE of 5.05% under AM 1.5G illumination at the thickness of 40 nm which is competitive with spiro-OMe TAD at the same condition. The present work suggests a guideline for optimizing the photovoltaic properties of perovskite solar cells using the TiOPc as the HTM.     

Realizing high photovoltage for inverted planar heterojunction perovskite solar cells

<正>Inverted planar heterojunction perovskite solar cells (peroSCs) have caused tremendous attention due to their promise features of easy fabrication and compatibility with flexible substrates [1]. However, their power conversion efficiencies(PCE) are greatly limited by its relatively low open-circuit voltage (Voc), which is attributed to high nonradiative recombination losses owing to the existence of high density of     

Recent progress of inverted organic-inorganic halide perovskite solar cells

In recent years, inverted perovskite solar cells(IPSCs) have attracted significant attention due to their low-temperature and cost-effective fabrication processes, hysteresis-free properties, excellent stability,and wide application. The efficiency gap between IPSCs and regular structures has shrunk to less than 1%. Over the past few years, IPSC research has mainly focused on optimizing power conversion efficiency to accelerate the development of IPSCs. This review provides an overview of recent...     

Cross-linked hole transport layers for high-efficiency perovskite tandem solar cells

Science China Chemistry - Perovskite tandem solar cells have recently received extensive attention due to their promise of achieving power conversion efficiency (PCE) beyond the limits of...     

Heteroatom engineering on spiro-type hole transporting materials for perovskite solar cells

A series of spiro-type hole transporting materials, spiro-OMe TAD, spiro-SMe TAD and spiro-OSMe TAD,with methoxy, methylsulfanyl or half methoxy and half methylsulfanyl terminal groups are designed and prepared. The impact of varied terminal groups on bulk properties, such as photophysical, electrochemical, thermal, hole extraction, and photovoltaic performance in perovskite solar cells is investigated.It is noted that the terminal groups of the hole transporting material with half methoxy and h...     

High isotropic dispiro structure hole transporting materials for planar perovskite solar cells

Two novel fluorene-based hole transporting materials(HTMs) were synthesized to be used in perovskite solar cells(PSCs). C102 was designed based on C101 by simply linking the two carbon–carbon single bonds to compose a "dispiro" structure. Their typically similar structures cause them sharing almost the same energy levels. However, their photovoltaic performances are quite different due to the small variations. The PSC that contained the "dispiro" structure, C102, reached a power conversion efficiency(PCE)of 17.4%, while the device contained C101, obtained a lower PCE of 15.5%. Electrochemical properties and Photovoltaic characterization of the two materials have been investigated to explain the result. It is shown that C102 has a stronger ability to transport holes and resist the charge recombination. Thus, the dispiro structure should be more appropriate being used as HTM in PSCs.     

Development of electron and hole selective contact materials for perovskite solar cells

Nowadays, both n-i-p and p-i-n perovskite solar cells (PSCs) device structures are reported to give high performance with photo conversion efficiencies (PCEs) above 20%. The efficiency of the PSCs is fundementally determined by the charge selective contact materials. Hence, by introducing proper contact materials with good charge selectivity, one could potentially reduce interfacial charge recombination as well as increase device performance. In the past few years, copious charge selective contact materials have been proposed. Significant improvements in the corresponding devices were observed and the reported PCEs were close to that of classic Spiro-OMeTAD. This mini-review summarizes the state-of-the-art progress of typical electron/hole selective contact materials for efficient perovskite solar cells and an outlook to their development is made.     

Evaporated potassium chloride for double-sided interfacial passivation in inverted planar perovskite solar cells

Defect-induced charge carrier recombination at the interfaces between perovskite and adjacent charge transport layers restricts further improvements in the device performance of perovskite solar cells(PSCs).Defect passivation at these interfaces can reduce trap states and inhibit the induced nonradiative recombination.Herein,we report a double-sided interfacial passivation via simply evaporating potassium chloride(DIP-KCl)at both the hole transport layer(HTL)/perovskite and perovskite/electron transport layer(ETL)interfaces in inverted planar PSCs.We demonstrate that the bottom KCl layer at the HTL/perovskite interface not only reduces the interfacial defects and improves the interfacial contact,but also leads to increased perovskite crystallinity,while the top KCl layer at the perovskite/ETL interface efficiently passivates the perovskite top surface defects and facilitates electron extraction at this interface.Thus,suppressed nonradiative recombination and faster charge extraction at both interfaces close to the perovskite layer can be achieved by using our DIP-KCl strategy.As a result,inverted PSCs based on DIP-KCl present an increased efficiency from 17.1% to 19.2% and enhanced stability,retaining over 90% of their initial efficiency after aging at maximum power point tracking for 1000 h.This work provides a simple and efficient way for defect passivation to further increase the efficiency and stability of PSCs.     

Novel donor-acceptor-donor structured small molecular hole transporting materials for planar perovskite solar cells

Novel donor-acceptor-donor structured small molecular hole transporting materials are developed through a facile route by crosslinking dithienopyrrolobenzothiadiazole and phenothiazine or triarylamine-based donor units. The strong push/pull electron capability of dithienopyrrolobenzothiadiazole/phenothiazine and large π-conjugated dithienopyrrolobenzothiadiazole facilitate hole mobility and high conductivity. The devices using the dithienopyrrolobenzothiadiazole/phenothiazine-based hole transporting material achieved a power conversion efficiency of 14.2% under 1 sun illumination and improved stability under 20% relative humidity at room temperature without encapsulation. The present finding highlights the potential of dithienopyrrolobenzothiadiazole-based donor-acceptor-donor small molecular hole transporting materials for perovskite solar cells.     

Minimizing interfacial energy losses in inverted perovskite solar cells by a dipolar stereochemical 2D perovskite interface

Inverted perovskite solar cells(PSCs) have attracted broad research and industrial interest owing to their suppressed hysteresis,cost-effectiveness,and easy-fabrication.However,the issue of non-radiative recombination losses at the n-type interface between the perovskite and fullerene has impeded further improvement of photovoltaic performance.Here,we modify the n-type interface of FAPbI₃ perovskite films by constructing a stereochemical two-dimensional(2D) perovskite interlayer,in wh...     

Spatial configuration engineering of perylenediimide-based non-fullerene electron transport materials for efficient inverted perovskite solar cells

Due to their excellent photoelectron chemical properties and suitable energy level alignment with perovskite,perylene diimide(PDI)derivatives are competitive non-fullerene electron transport material(ETM)candidates for perovskite solar cells(PSCs).However,the conjugated rigid plane structure of PDI units result in PDI-based ETMs tending to form large aggregates,limiting their application and photovoltaic performance.In this study,to restrict aggregation and further enhance the photovoltaic performance of PDI-type ETMs,two PDI-based ETMs,termed PDO-PDI2(dimer)and PDO-PDI3(trimer),were constructed by introducing a phenothiazine 5,5-dioxide(PDO)core building block.The research manifests that the optoelectronic properties and film formation property of PDO-PDI2 and PDO-PDI3 were deeply affected by the molecular spatial configuration.Applied in PSCs,PDO-PDI3 with threedimensional spiral molecular structure,exhibits superior electron extraction and transport properties,further achieving the best PCE of 18.72%and maintaining 93%of its initial efficiency after a 720-h aging test under ambient conditions.     

Improved interfacial property by small molecule ethanediamine for high performance inverted planar perovskite solar cells

We report a simple and effective method to realize desirable interfacial property for inverted planar perovskite solar cells(PSCs)by using small molecule ethanediamine for the construction of a novel polyelectrolyte hole transport material(P3CT-ED HTM).It is found that P3CT-ED can not only improve the hole transport property of P3CT-K but also improve the crystallinity of adjacent perovskite film.In addition,the introduction of ethanediamine into P3CT realigns the conduction and valence bands upwards,passivates surface defects and reduces nonradiative recombination.As a consequence,compared to P3CT-K hole transport layer(HTL)based devices,the average power conversion efficiency(PCE)is boosted from17.2% to 19.6% for the counterparts with P3CT-ED,with simultaneous enhancement in open circuit voltage and fill factor.The resultant device displays a champion PCE of 20.5% with negligible hysteresis.     

Inorganic p-type semiconductors and carbon materials based hole transport materials for perovskite solar cells

Incorporation of proper inorganic p-type semiconductors as hole transport layer has great potential to increase long-term stability while maintaining high power conversion efficiency of perovskite solar cells with low material cost.     

Intrinsic thermal stability of inverted perovskite solar cells based on electrochemical deposited PEDOT

Thermal stability of perovskite materials is an issue impairing the long-term operation of inverted perovskite solar cells(PSCs). Herein, the thermal attenuation mechanism of the MAPb I3films that deposited on two different hole transport layers(HTL), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS) and poly(3,4-ethylenedioxythiophene)(PEDOT), is comprehensively studied by applying a heat treatment at 85 °C. The thermal stress causes the mutual ions migration of I, Pb and Ag t...     

Solution-processed CuOx as an efficient hole-extraction layer for inverted planar heterojunction perovskite solar cells

A solution-processed CuO_x film has been successfully integrated as the hole-transporting layer (HTL) for inverted planar heterojunction perovskite solar cells (PVSCs). The CuO_x layer is fabricated by simply spin-coating a copper acetylacetonate (Cu(acac)₂) chloroform solution onto ITO glass with high transparency in the visible range. The compact and pinhole-free perovskite film with large grain domains is grown on the CuO_x film. The inverted PVSCs with the structure of ITO/CuO_x/MAPbI₃/PC₆₁BM/ZnO/Al are fabricated and show a best PCE of 17.43% under standard AM 1.5G simulated solar irradiation with a V_OC of 1.03 V, a J_SC of 22.42 mA cm^-2, and a fill factor of 0.76, which is significantly higher and more stable than that fabricated from the often used hole-transporting material PEDOT:PSS (11.98%) under the same experimental conditions. The enhanced performance is attributed to the efficient hole extraction through the CuO_x layer as well as the high-quality CH₃NH₃PbI₃ films grown on the CuO_x. Our results indicate that low-cost and solution-processed CuO_x film is a promising HTL for high performance PVSCs with better stability.     

Spin-coated copper(I) thiocyanate as a hole transport layer for perovskite solar cells

Journal of Solid State Electrochemistry - Application of a low-cost and efficient p-type inorganic hole-transporting material, copper thiocyanate (CuSCN), on mesoporous n-i-p-configurated...     

Planar core based starburst triphenylamine molecules as hole transporting materials for high-performance perovskite solar cells

<正>Starburst triphenylamine molecules are generally used as hole transporting materials (HTMs) for optoelectronic devices like solar cells, light emitting diode and field effect transistors [1]. The use of starburst triphenylamine molecules like spiro-OMeTAD HTM initiated the construction of solid state perovskite solar cells (PSCs)[2,3]. Currently, based on triphenylamine HTMs, the highest power conversion efficiency (PCE) of PSCs is up to 22.1%[4]. Nowadays, spiro-