Chen Weijie

Hole transport layer (HTL) is of great importance to carbon electrode perovskite solar cells. This study develops an organic/inorganic HTL bilayer to enhance electrical and mechanical contact at anode buffer interfaces. The modified HTL delivers a state-of-the-art efficiency of 20.8% for perovskite solar cells with both blade-coated active layer and carbon electrode.

Abstract

Perovskite solar cells with carbon electrode have a commercial impact because of their facile scalability, low-cost, and stability. In these devices, it remains a challenge to design an efficient hole transport layer (HTL) for robust interfacing with perovskite on one side and carbon on another. Herein, an organic/inorganic double planar HTL is constructed based on polythiophene (P3HT) and nickel oxide (NiOx) nanoparticles to address the named challenge. Through adding an alkyl ammonium bromide (CTAB) modified NiOx nanoparticle layer on P3HT, the planar HTL achieves a cascade type-II energy level alignment at the perovskite/HTL interfaces and a preferential ohmic contact at NiOx/carbon electrode, which greatly benefits in charge collection while suppressing charge transfer recombination. Besides, compared with the single P3HT layer, the planar composite enables a robust interfacial contact by protecting perovskite from being corroded by carbon paste during fabrication. As a result, the blade-coated FA_0.6MA_0.4PbI₃ perovskite solar cells (fabricated in ambient air in fume hood) with carbon electrode deliver an efficiency of 20.14%, the highest value for bladed coated carbon and perovskite solar cells, and withstand 275 h maximum power point tracking in air without encapsulation (95% efficiency retained).

Publication date: July 2023

Source: Nano Energy, Volume 112

Author(s): Atefeh Yadegarifard, Haram Lee, Hae-Jun Seok, Inho Kim, Byeong-Kwon Ju, Han-Ki Kim, Doh-Kwon Lee

A new interface modification strategy for TiO₂ via FAI@ZIF-8 is demonstrated. After the FAI@ZIF-8 modification, the FA⁺ and I⁻ released from the ZIF-8 pores in the modified layer fill the iodide and formamidine ions vacancies produced during annealing of perovskite film, reducing defects and improving stability of the FAI@ZIF-8-treated device.

The efficiency of perovskite solar cells (PSCs) has surpassed all other thin-film solar cells. It is well known that the mismatch between the perovskite film and electron transport layer is an important factor to damage the stability of PSCs. Herein, an effective modification strategy to improve stability by using FAI@ZIF-8 is demonstrated. It is found that the FAI@ZIF-8 modification reduces the trap-state density of the perovskite by slowly releasing FAI from the ZIF-8 pore. Besides, FAI@ZIF-8 improves energy-level alignment at TiO₂/perovskite interface, which facilitates electron extraction at the interface. As a consequence, an optimal power conversion efficiency (PCE) of 23.52% is achieved for the FAI@ZIF-8-treated PSCs. After storing under 20–30% relative humidity and room temperature for 2000 h, the FAI@ZIF-8-treated device sustains 96% of its initial PCE; nevertheless, the control device maintains only 73% of its initial PCE under the same conditions. This strategy is helpful to guide the development of high-performance PSCs and promotes commercialization of perovskite materials.

Herein, a novel multilayer electrode has been developed based on the atomic layer deposition technique and vacuum thermal evaporation. The semitransparent perovskite solar cells made with the novel multilayer anode show superior photovoltaic performance and optical transmittance compared to devices with ultrathin metal anode. An effective method to realize the preparation of high-efficiency translucent perovskite photovoltaic devices is provided.

Semitransparent perovskite solar cells (ST-PSCs) have recently shown their significance in building-integrating photovoltaics. Normally, the conductivity and transparency of the top electrode directly affects the properties of the ST-PSC. The transparency of metal electrodes is extremely sensitive to thickness, but an ultrathin metal film (<10 nm) shows an unexpectedly low conductivity. Herein, a sandwich-type transparent conductive electrode is designed by combining atomic layer deposition ZnO and thermally evaporated Ag films, and proved that its film conductivity and optical transmittance are superior to metal electrodes with the same thickness. By using an optimized solution-based thin and continuous CH₃NH₃PbI₃ (MAPbI₃) film as the light absorber layer, the ST-PSCs demonstrate a power conversion effiency of 10% and an average visible transmittance of 19.6%. The results illustrate a strategy of novel structure designs for the electrode to overcome the contradiction between the efficiency and transparency of ST-PSCs.

Prolinamide (ProA) is introduced into the PbI₂ precursor solution, which improves the performance of perovskite solar cells (PSCs) by the competitive crystallization and efficient defect passivation of perovskite. The results indicate that ProA can lead to the increase of the energy barrier of crystallization and slows down the crystallization rate. Notably, ProA-assisted PSCs achieve 24.61% power conversion efficiency and high stability.

Abstract

Defects of perovskite (PVK) films are one of the main obstacles to achieving high-performance perovskite solar cells (PSCs). Here, the authors fabricated highly efficient and stable PSCs by introducing prolinamide (ProA) into the PbI₂ precursor solution, which improves the performance of PSCs by the competitive crystallization and efficient defect passivation of perovskite. The theoretical and experimental results indicate that ProA forms an adduct with PbI₂, competes with free I⁻ to coordinate with Pb²⁺, leads to the increase of the energy barrier of crystallization, and slows down the crystallization rate. Furthermore, the dual-site synergistic passivation of ProA is revealed by density functional theory (DFT) calculations and experimental results. ProA effectively reduces non-radiative recombination in the resultant films to improve the photovoltaic performance of PSCs. Notably, ProA-assisted PSCs achieve 24.61% power conversion efficiency (PCE) for the champion device and the stability of PSCs devices under ambient and thermal environments is improved.

Improving the cooperative interactions between halogenated aromatic additive DIB and aromatic side chain Y-type acceptors induced increased crystallinity of acceptor molecules in a high-performance polymorph, leading to the elevated power conversion efficiencies of 18.03% and 19.22% in binary and ternary blend devices.

Abstract

Processing additive plays an important role in the standard operation procedures for fabricating top performing polymer solar cells (PSCs) through efficient interactions with key photovoltaic materials. However, improving interaction study of acceptor materials to high performance halogenated aromatic additives such as diiodobenzene (DIB) is a widely neglected route for molecular engineering toward more efficient device performances. In this work, two novel Y-type acceptor molecules of BTP-TT and BTP-TTS with different aromatic side chains on the outer positions are designed and synthesized. The resulting aromatic side chains significantly enhanced the interactions between the acceptor molecules and DIB through an arene/halogenated arene interaction, which improved the crystallinity of the acceptor molecules and induced a polymorph with better photovoltaic performances. Thus, high power conversion efficiencies (PCEs) of 18.04% and 19.22% are achieved in binary and ternary blend devices using BTP-TTS as acceptor and DIB as additive. Aromatic side chain engineering for improving additive interactions is proved to be an effective strategy for achieving much higher performance photovoltaic materials and devices.

The trichloroacetyl chloride can effectively passivate the perovskite surface defects and tend to generate an electronic barrier layer cesium chloride acetate which promote gradient energy level arrangement, thus significantly improving the power conversion efficiency and stability of HTL-free CsPbI₃ C-PSCs.

Abstract

In order to improve the thermal stability of perovskite solar cells (PSCs) and reduce production costs, hole transport layer (HTL)-free carbon-based CsPbI₃ PSCs (C-PSCs) have attracted the attention of researchers. However, the power conversion efficiency (PCE) of HTL-free CsPbI₃ C-PSCs is still lower than that of PSCs with HTL/ metal electrodes. This is because the direct contact between the carbon electrode and the perovskite layer has a higher requirement on the crystal quality of perovskite layer and matched energy level at perovskite/carbon interface. Herein, the acyl chloride group and its derivative trichloroacetyl chloride are used to passivate CsPbI₃ C-PSCs for the first time. The results show that the carbonyl group of trichloroacetyl chloride can effectively passivate the uncoordinated Pb²⁺ ions in perovskite. At the same time, leaving group Cl⁻ ions can increase the grain size of perovskite and improve the crystallization quality of perovskite layer. In addition, the trichloroacetyl chloride tends to generate cesium chloride acetate, which acts as an electron blocking layer, reduces charge recombination, promotes gradient energy level arrangement, and effectively improves the separation and extraction ability of carriers. The PCE of CsPbI₃ HTL-free C-PSCs is successfully increased from 13.40% to 14.82%.

The impact of the amorphous–crystalline (a–c) interface on the blocking performance of ZrN _x barrier films is investigated and the interface density is quantified for proving the interdiffusion channels by pattern recognition technology. The underlying mechanisms of a–c interfaces for blocking effects are further revealed in thermodynamic and kinetics properties, constructing stable inverted perovskite solar cells with amorphous ZrN _x barriers.

Abstract

It is challenging to achieve long-term stability of perovskite solar cells due to the corrosion and diffusion of metal electrodes. Integration of compact barriers into devices has been recognized as an effective strategy to protect the perovskite absorber and electrode. However, the difficulty is to construct a thin layer of a few nanometers that can delay ion migration and impede chemical reactions simultaneously, in which the delicate microstructure design of a stable material plays an important role. Herein, ZrN _x barrier films with high amorphization are introduced in p–i–n perovskite solar cells. To quantify the amorphous–crystalline (a–c) density, pattern recognition techniques are employed. It is found the decreasing a–c interface in an amorphous film leads to dense atom arrangement and uniform distribution of chemical potential, which retards the interdiffusion at the interface between ions and metal atoms and protect the electrodes from corrosion. The resultant solar cells exhibit improved operational stability, which retains 88% of initial efficiency after continuous maximum power point tracking under 1-Sun illumination at room temperature (25 °C) for 1500 h.

Publication date: Available online 27 April 2023

Source: Joule

Author(s): Yuhao Wang, Matthew James Robson, Alessandro Manzotti, Francesco Ciucci

Publication date: 17 May 2023

Source: Joule, Volume 7, Issue 5

Author(s): Wenxuan Wang, Yong Cui, Tao Zhang, Pengqing Bi, Jianqiu Wang, Shiwei Yang, Jingwen Wang, Shaoqing Zhang, Jianhui Hou

Using 4-tert-Butyl-1-(ethoxycarbonyl- methoxy) thiacalix[4]arene (tBuTCA) to complex with the cations and out-of-cage (Lead(II) iodide) PbI₂ so that to compensate electrons for iodine vacancy defect. The negative charge compensation for iodine vacancy can hinder the formation of Pb-Pb dimer.

Abstract

Although there is extensive attention to the eminent perovskite solar cells, the deep-level defects such as Pb-Pb dimers in the solution-processed polycrystalline perovskites inevitably result in photovoltaic output losses and subsequent degradation. Recently, it is reported that an electron-donating group can passivate Pb dimer defects efficiently. However, the mechanism for the causation of metallic lead (Pb⁰) from the iodide vacancy (V_I) is unclear. Herein, a chain reaction mechanism is proposed for the possible transformation process from V_I to Pb⁰ with the Pb dimer intermediates. In this regard, a host-guest strategy is adopted by using 4-tert-Butyl-1-(ethoxycarbonyl- methoxy) thiacalix[4]arene (tBuTCA) to complex with the cations and out-of-cage (Lead(II) iodide) PbI₂. Moreover, a host-guest complexation can be formed due to the Pb²⁺-π interactions. Continuously, the negative charge compensation for iodine vacancy can hinder the formation of Pb-Pb dimer, thus significantly suppressing non-radiative recombination. Consequently, the resulting solar cells show more than 24% power conversion efficiencies and maintain over 96% of their initial performance without encapsulation for 486 h under an ambient environment. This work highlights the significance of supramolecular engineering in constructing a high-quality perovskite for efficient and stable perovskite solar cells.

An easy isomerization strategy for additives enables more reasonable molecular spatial distribution and better π–π stacking behavior of bulk heterojunction, which provides guidance for screening and designing additives with excellent morphology improvement capability and is expected to have a profound influence on further increasing efficiency of organic solar cells without adopting the isomerization strategy for active molecules possessing complex conjugated backbones and branched chains.

Abstract

The morphological features of the active layer has always been an important factor limiting the efficiency of organic solar cells (OSCs). Although halogen-based additives capable of forming non-covalent bonds with active molecules can effectively adjust the morphology of active layer, the inner mechanism of positional isomerization of additives on the crystallization kinetics of bulk heterojunction has been ignored, which hinders further development of this technique. Herein, a new additive-assisted optimization strategy for high-efficiency OSCs based on three positional isomeric additives is proposed, which have different sites for two bromine substituents on the benzene ring. The results demonstrate that symmetrically structured additives with the smallest dipole moment, the lowest steric hindrance and the most uniformly distributed electrostatic potential, can form more suitable non-covalent interactions with the acceptor, resulting in more reasonable molecular spatial distribution and better π–π stacking behavior. For other non-fullerene systems, the symmetrically structured additive also shows the best effect on optimizing molecular aggregation and stacking. This work provides guidance for screening and designing additives with excellent morphology improvement capability and is expected to have a profound influence on further increasing efficiency of OSCs without adopting the isomerization strategy for active molecules possessing complex conjugated backbones and branched chains.

The double-edged sword effects of the methylammonium chloride (MACl) additive on the properties of perovskite films and solar cells are presented. Methylammonium lead mixed-halide perovskite (MAPbI_{3− x} Cl _x ) films suffer from undesirable morphology evolution during annealing, resulting in extra defects to deteriorate optoelectronic properties and device performance. The FAX (FA = formamidinium, X = I, Br, and Ac) post-treatment strategy is developed to inhibit the morphology transition and suppress defects.

Abstract

The additive engineering strategy promotes the efficiency of solution-processed perovskite solar cells (PSCs) over 25%. However, compositional heterogeneity and structural disorders occur in perovskite films with the addition of specific additives, making it imperative to understand the detrimental impact of additives on film quality and device performance. In this work, the double-edged sword effects of the methylammonium chloride (MACl) additive on the properties of methylammonium lead mixed-halide perovskite (MAPbI_3-xCl_x ) films and PSCs are demonstrated. MAPbI_3-xCl_x films suffer from undesirable morphology transition during annealing, and its impacts on the film quality including morphology, optical properties, structure, and defect evolution are systematically investigated, as well as the power conversion efficiency (PCE) evolution for related PSCs. The FAX (FA = formamidinium, X = I, Br, and Ac) post-treatment strategy is developed to inhibit the morphology transition and suppress defects by compensating for the loss of the organic components, a champion PCE of 21.49% with an impressive open-circuit voltage of 1.17 V is obtained, and remains over 95% of the initial efficiency after storing over 1200 hours. This study elucidates that understanding the additive-induced detrimental effects in halide perovskites is critical to achieve the efficient and stable PSCs.

The cross-linked perovskite and phenyl-C61-butyric acid methyl ester (PCBM) layers by polydimethylsiloxane (PDMS) are applied. The hydrogen bond and Lewis acid–base interaction between PDMS and perovskite precursors effectively reduce formamidinium vacancy, passivating uncoordinated Pb defects and improving perovskite stability. Also, PDMS in the PCBM layer can suppress the auto-aggregation of the PCBM under light and thermal stress.

The operational stability of p–i–n perovskite solar cells (PSCs) is dramatically subjected to the quality of the perovskite light harvester and the interface layer atop the perovskite. Herein, a dual crosslinked functional layer strategy of using the versatile polydimethylsiloxane as an additive both in the perovskite layer and in phenyl-C61-butyric acid methyl ester interface layer, to improve the device tolerance against light, thermal, humidity, and bending stress, is reported. As a result, a promising power conversion efficiency of 21.6% (stabilized at 21.3%) for nickel oxide-based p–i–n PSCs is achieved. In addition, the unencapsulated devices maintain 97% of their initial efficiencies after continuous operation under 1 sun equivalent illumination at 60 °C with maximum power point tracking for 1000 h and 80% of their initial efficiencies exposed in ambient air for 500 h. The application of the aforementioned strategy in the flexible device also improves the bending mechanical stability, of which the corresponding flexible devices maintain 85% of their initial efficiencies after 1000 cycles at a radius of 8 mm.

A series of novel self-assembled molecules (SAMs) is synthesized and successfully used to modify the interfacial layer between poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) and perovskite. The introduction of SAMs improves interfacial contact, reduces nonradiative recombination, and improves the quality of perovskite films. Consequently, the all-perovskite tandem solar cell with an efficiency of 25.24% is realized.

Abstract

This study is on the enhancement of the efficiency of wide bandgap (FA_0.8Cs_0.2PbI_1.8Br_1.2) perovskite solar cells (PSCs) used as the top layer of the perovskite/perovskite tandem solar cell. Poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) and the monomolecular layer called SAM layer are effective hole collection layers for APbI₃ PSCs. However, these hole transport layers (HTL) do not give high efficiencies for the wide bandgap FA_0.8Cs_0.2PbI_1.8Br_1.2 PSCs. It is found that the surface-modified PTAA by monomolecular layer (MNL) improves the efficiency of PSCs. The improved efficiency is explained by the improved FA_0.8Cs_0.2PbI_1.8Br_1.2 film quality, decreased film distortion (low lattice disordering) and low density of the charge recombination site, and improves carrier collection by the surface modified PTAA layer. In addition, the relationship between the length of the alkyl group linking the anchor group and the carbazole group is also discussed. Finally, the wide bandgap lead PSCs (E _g = 1.77 eV) fabricated on the PTAA/monomolecular bilayer give a higher power conversion efficiency of 16.57%. Meanwhile, all-perovskite tandem solar cells with over 25% efficiency are reported by using the PTAA/monomolecular substrate.

A simple solution-processable passivator is introduced on the top surface of low-dimensional 2D perovskites. This passivator induces a vertical crystal orientation and simultaneously passivates the defects on the perovskites, leading to efficient charge transport with reduced recombination loss in the photoactive materials. The champion device exhibits a power conversion efficiency of 20.05% with negligible hysteresis and superior operational stability.

Abstract

Solar cells (PSCs) with quasi-2D Ruddlesden–Popper perovskites (RPP) exhibit greater environmental stability than 3D perovskites; however, the low power conversion efficiency (PCE) caused by anisotropic crystal orientations and defect sites in the bulk RPP materials limit future commercialization. Herein, a simple post–treatment is reported for the top surfaces of RPP thin films (RPP composition of PEA₂MA₄Pb₅I₁₆ <n> = 5) in which zwitterionic n-tert-butyl-α-phenylnitrone (PBN) is used as the passivation material. The PBN molecules passivate the surface and grain boundary defects in the RPP and simultaneously induce vertical direction crystal orientations of the RPPs, which lead to efficient charge transport in the RPP photoactive materials. With this surface engineering methodology, the optimized devices exhibit a remarkably enhanced PCE of 20.05% as compared with the devices without PBN (≈17.53%) and excellent long-term operational stability with 88% retention of the initial PCE under continuous 1-sun irradiation for over 1000 h. The proposed passivation strategy provides new insights into the development of efficient and stable RPP-based PSCs.

Herein, the electron acceptor molecule 1,2,4,5-tetracyanobenzene is utilized to trigger intermolecular π–π interaction along with the electronic doping of 2D/3D perovskite to facilitate carrier transportation. It effectively reduces defect density and optimizes energy level alignment. As a result, the 2D/3D perovskite solar cell achieves a champion PCE of up to 24.01 % coupled with greatly strengthened environmental stability.

Abstract

Although the incorporation of 2D perovskite into 3D perovskite can greatly enhance intrinsic stability, power conversion efficiency (PCE) of 2D/3D perovskite is still inferior to its 3D counterpart due to poor carrier transport kinetics resulted from the quantum and dielectric confinement of 2D component. To overcome this issue, the electron acceptor molecule 1,2,4,5-tetracyanobenzene (TCNB) was introduced to trigger intermolecular π–π interaction in 2D perovskite along with the electronic doping of 2D/3D perovskite to improve charge transfer efficiency. By virtue of high electron affinity, TCNB can undergo electron transfer reaction and subsequently establish π–π interaction with 1-naphthalenemethylammonium (NMA) cations, greatly strengthening lattice rigidity and reducing exciton binding energy. Transmission electron microscopy results demonstrate that 2D phases are mainly distributed at grain boundaries, reducing defect density and weakening nonradiative recombination. Meanwhile, the p-type doping of perovskite by TCNB optimizes energy level alignment at perovskite/hole transport layer interface. Consequently, PCE of champion device is significantly boosted to 24.01 %. The unencapsulated device retains an initial efficiency close to 94 % after exposure to ambient environment for over 1000 h. This work paves a novel path for designing new mixed-dimensional perovskite solar cells with high PCE and superior stability.

Two vinyl π-spacer linking-site isomerized giant molecule acceptors (GMAs) EV-i and EV-o were synthesized and applied in non-halogenated solvent o-xylene (o-XY) processed organic solar cells (OSCs). The EV-i based OSC exhibits suitable phase separation in active layer, which contributes to a higher power conversion efficiency (PCE) of 18.27 %, while the EV-o based OSCs show a poor PCE of 2.50 % due to its excessive aggregation.

Abstract

High efficiency organic solar cells (OSCs) based on A-DA′D-A type small molecule acceptors (SMAs) were mostly fabricated by toxic halogenated solvent processing, and power conversion efficiency (PCE) of the non-halogenated solvent processed OSCs is mainly restricted by the excessive aggregation of the SMAs. To address this issue, we developed two vinyl π-spacer linking-site isomerized giant molecule acceptors (GMAs) with the π-spacer linking on the inner carbon (EV-i) or out carbon (EV-o) of benzene end group of the SMA with longer alkyl side chains (ECOD) for the capability of non-halogenated solvent-processing. Interestingly, EV-i possesses a twisted molecular structure but enhanced conjugation, while EV-o shows a better planar molecular structure but weakened conjugation. The OSC with EV-i as acceptor processed by the non-halogenated solvent o-xylene (o-XY) demonstrated a higher PCE of 18.27 % than that of the devices based on the acceptor of ECOD (16.40 %) or EV-o (2.50 %). 18.27 % is one of the highest PCEs among the OSCs fabricated from non-halogenated solvents so far, benefitted from the suitable twisted structure, stronger absorbance and high charge carrier mobility of EV-i. The results indicate that the GMAs with suitable linking site would be the excellent candidates for fabricating high performance OSCs processed by non-halogenated solvents.

Publication date: August 2023

Source: Journal of Energy Chemistry, Volume 83

Author(s): Wu Liu, Ning Meng, Xiaomin Huo, Yao Lu, Yu Zhang, Xiaofeng Huang, Zhenqun Liang, Suling Zhao, Bo Qiao, Zhiqin Liang, Zheng Xu, Dandan Song

Difluorobenzoxadiazole (ffBX) unit is introduced into the skeleton of PBDB-TF as the third comonomer to reduce the energy loss and poor batch-to-batch reproducibility. The resulting polymer PBFBX20 exhibits suppressed energy loss and insensitivity to molecular weight when 20% ffBX is added. This result implies that the ffBX unit can be a promising monomer in constructing high-performance polymer donors.

Developing high-performance polymer donors is of great importance to further improve the photovoltaic performances of organic solar cells (OSCs). However, most polymer donors suffer from mismatching energy levels and poor batch-to-batch reproducibility, which hinder the further enhancement of device performance and their potential in a commercial application. Constructing random terpolymers with a third monomer is considered a practical way to solve these problems. Herein, the 5,6-difluorobenzo[c][1,2,5]oxadiazole (ffBX) unit is incorporated into the skeleton of PBDB-TF as the third comonomer to construct random terpolymers. The terpolymers exhibit downshifted the highest occupied molecular orbital energy levels than PBDB-TF, which is beneficial for obtaining higher open-circuit voltage and lower energy loss of the OSCs. The OSCs based on PBFBX20:Y6-BO demonstrate high power conversion efficiency of 17.5%. Moreover, PBFBX20 exhibits excellent batch-to-batch reproducibility. Five polymer batches with molecular weights ranging from 20.0 to 54.0 kDa produced very similar PCEs. This work demonstrates the bright future of ffBX-contained terpolymers in realizing high-performance OSCs and further applying in the OSCs community.

Recent progress on all polymer solar cells (APSCs) is summarized as (1) materials innovation involving polymerized small molecule acceptors, polymer donors, and interfacial modification layer; (2) device engineering including solvent and additive treatment, layer by layer processing method and ternary strategy. Challenges and new insights on future research directions are suggested for pushing forward the development of efficient APSCs.

All polymer solar cells (APSCs) composed of polymeric donors and acceptors have attracted tremendous attention due to their unique merits of mechanical flexibility and good film formation property, which exhibit promising applications on wearable and flexible stretchable devices. Over 18% power conversion efficiency of APSCs has been achieved benefiting from the continuous development of functional layer materials innovation and device engineering evolution. In this review, the functional layer materials that enabled the recent progress of efficient APSCs are outlined, including typical polymer donors, emerging polymer acceptors based on polymerizing small molecule acceptors strategy, interfacial materials as well as the rational design rules for corresponding functional materials. From the perspective of device engineering evolution, the film deposition and treatment techniques are introduced, which play a vital role in manipulating film morphology through properly tuning the vertical component distribution and aggregation behavior of polymers. Meanwhile, the ternary strategy is also discussed as an effective method in promoting mechanical durability, stability, and thickness-insensitive characteristics of APSCs facing for future applications. The challenges and outlooks on this filed are finally proposed for developing high-performance APSCs.

The aluminum oxide (Al₂O₃) nanoparticles are imbedded into the buried interface, which fills the voids and grain boundaries of perovskite, leading to compact morphology and reduced dangling bonds and defects. The suppressed trap-assisted recombination, better energy alignment, and decreased J–V hysteresis in the modified device with Al₂O₃ nanoparticles and phenethylammonium bromide contribute to a significant increase in voltage and stability.

Abstract

Stability and scalability are essential and urgent requirements for the commercialization of perovskite solar cells (PSCs), which are retarded by the non-ideal interface leading to non-radiative recombination and degradation. Extensive efforts are devoted to reducing the defects at the perovskite surface. However, the effects of the buried interface on the degradation and non-radiative recombination need to be further investigated. Herein, an omnibearing strategy to modify buried and top surfaces of perovskite film to reduce interfacial defects, by incorporating aluminum oxide (Al₂O₃) as a dielectric layer and growth scaffolds (buried surface) and phenethylammonium bromide as a passivation layer (buried and top surfaces), is demonstrated. Consequently, the open-circuit voltage is extensively boosted from 1.02 to 1.14 V with the incorporation of Al₂O₃ filling the voids between grains, resulting in dense morphology of buried interface and reduced recombination centers. Finally, the impressive efficiencies of 23.1% (0.1 cm²) and 22.4% (1 cm²) are achieved with superior stability, which remain 96% (0.1 cm²) and 89% (1 cm²) of its initial performance after 1200 (0.1 cm²) and 2500 h (1 cm²) illumination, respectively. The dual modification provides a universal method to reduce interfacial defects, revealing a promising prospect in developing high-performance PSCs and modules.

Pemirolast potassium (PP) is employed to passivate Pb²⁺ and I atom defects, the release of residual stress can be effectively extended from the surface to the entire perovskite layer. Moreover, the superior carrier extraction/transport and better energy level alignment, yields an exceptional efficiency over 23% with an ultra-high fill factor of 84.36% for inverted perovskite solar cells.

Abstract

The quality of the perovskite absorption layer is critical for the high efficiency and long-term stability of perovskite solar cells (PSCs). The inhomogeneity due to local lattice mismatch causes severe residual strain in low-quality perovskite films, which greatly limits the availability of high-performance PSCs. In this study, a multi-active-site potassium salt, pemirolast potassium (PP), is added to perovskite films to improve carrier dynamics and release residual stress. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) measurements suggest that the proposed multifunctional additive bonds with uncoordinated Pb²⁺ through the carbonyl group/tetrazole N and passivated I atom defects. Moreover, the residual stress release is effective from the surface to the entire perovskite layer, and carrier extraction/transport is promoted in PP-modified perovskite films. As a result, a champion power conversion efficiency (PCE) of 23.06% with an ultra-high fill factor (FF) of 84.36% is achieved in the PP-modified device, which ranks among the best in formamidinium-cesium (FACs) PSCs. In addition, the PP-modified device exhibits excellent thermal stability due to the inhibited phase separation. This work provides a reliable way to improve the efficiency and stability of PSCs by releasing residual stress in perovskite films through additive engineering.

To replace popular but toxic chlorobenzene series, CsPbI₃ nanocrystals functionalized alkanes with ultralow-polarity are utilized as green antisolvents successfully to fabricate high-quality and high-orientation perovskite films.

Abstract

To address the toxicity concern of extensively used chlorobenzene (CB) and toluene antisolvents, it is urgent to explore green and more efficient antisolvents. In this work, a general and highly reproducible methodology of employing CsPbI₃ nanocrystals (NCs) functionalized green alkanes with ultralow-polarity (Alkane/NCs) as antisolvents to fabricate high-quality perovskite films is reported. Compared with the CB processed, the perovskite films with much improved quality and high-orientation are achieved by the Alkane/NCs approach. NCs in the alkane antisolvents are proven to provide enough heterogeneous nuclei, solving effectively the discontinuous film problem encountered from using pure alkanes. Strikingly, the lattice anchoring effect of NCs accounts for the high-orientation growth of the perovskite films as revealed directly by cryo-electron microscopy (cryo-EM). Moreover, the phase segregation that easily occur in the CB processed perovskite film is successfully suppressed by the Alkane/NCs method. The optimal device conversion efficiency is enhanced from 21.59% to 23.10% from CB to octane (OCT)/NCs. Impressively, the alkane/NCs processed perovskite films and their devices exhibit much improved stability over CB, with the conversion efficiency remaining at 94% of its initial value after 500 h light soaking for OCT/NCs device, while the CB device fails at around 100 h.

ChPbI₃ was obtained by ChI treatment of the CsPbI₃ surface to construct a 1D/3D heterostructure, which significantly improves the defect-assisted recombination and stability of CsPbI₃. Benefiting from 1D/3D heterostructure, the assembled carbon-based perovskite solar cells (C-PSCs) delivered a champion/certified efficiency of 18.05 %/17.8 %.

Abstract

Defects in perovskite are key factors in limiting the photovoltaic performance and stability of perovskite solar cells (PSCs). Generally, choline halide (ChX) can effectively passivate defects by binding with charged point defects of perovskite. However, we verified that ChI can react with CsPbI₃ to form a novel crystal phase of one-dimensional (1D) ChPbI₃, which constructs 1D/3D heterostructure with 3D CsPbI₃, passivating the defects of CsPbI₃ more effectively and then resulting in significantly improved photoluminescence lifetime from 20.2 ns to 49.4 ns. Moreover, the outstanding chemical inertness of 1D ChPbI₃ and the repair of undesired δ-CsPbI₃ deficiency during its formation process can significantly enhance the stability of CsPbI₃ film. Benefiting from 1D/3D heterostructure, CsPbI₃ carbon-based PSCs (C-PSCs) delivered a champion efficiency of 18.05 % and a new certified record of 17.8 % in hole transport material (HTM)-free inorganic C-PSCs.