Chen Weijie

2,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2 H,6 H)-tetraone (Pyr-TPA), with superior defect passivation effect for perovskite and decent carrier transport properties, as well as ideal solubility, is developed.

Interfacial passivation is a crucial technique for improving the performance of perovskite solar cells (PSCs) by suppressing nonradiative recombination. Incorporating electron-rich functional groups into organic semiconductors can combine the advantages of Lewis bases and organic semiconductors to achieve defect passivation of perovskite films and interfacial charge transport improvement simultaneously. However, interlayers generated by organic semiconductors are often destroyed during the deposition of the hole transport layer (HTL) in n–i–p PSCs. This prevents the accurate evaluation of interfacial passivation effects. Herein, a pyromellitic derivative, 2,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2 H,6 H)-tetraone (Pyr-TPA), containing four carbonyl groups that can passivate defects and enhance hole transport while simultaneously acting as a stable interlayer at the perovskite/HTL interface due to its ideal solubility profile is introduced. As a result, Pyr-TPA as an interlayer can minimize nonradiative recombination loss, resulting in a power conversion efficiency of up to 24.16%. Additionally, the interfacial Pyr-TPA passivation layer also exhibits strong resistance to moisture and ion migration, leading to enhanced long-term ambient stability of PSCs based on this material. Findings provide valuable insights into developing efficient and stable PSCs with simple and effective organic semiconductor interfacial passivation materials.

Solid additive 1,3,5-tribromobenzene (TBB) with centrosymmetric structure shows excellent potential in optimizing molecular aggregation and stacking, tuning the donor-acceptor distribution in the vertical direction, and improving the device stability. In tandem with the synergistic effect of the sequential deposition processing method and thermal treatment, a champion power conversion efficiency of 18.5% is achieved with D18-Cl/L8BO as the photoactive layer.

Abstract

The sequential deposition method assists the vertical phase distribution in the photoactive layer of organic solar cells, enhancing power conversion efficiencies. With this film coating approach, the morphology of both layers can be fine-tuned with high boiling solvent additives, as frequently applied in one-step casting films. However, introducing liquid additives can compromise the morphological stability of the devices due to the solvent residuals. Herein, 1,3,5-tribromobenzene (TBB) with high volatility and low cost, is used as a solid additive in the acceptor solution and combined thermal annealing to regulate the vertical phase in organic solar cells composed of D18-Cl/L8-BO. Compared to the control cells, the devices treated with TBB and those that underwent additional thermal processing exhibit increased exciton generation rate, charge carrier mobility, charge carrier lifetime, and reduced bimolecular charge recombination. As a result, the TBB-treated organic solar cells achieve a champion power conversion efficiency of 18.5% (18.1% averaged), one of the highest efficiencies in binary organic solar cells with open circuit voltage exceeding 900 mV. This study ascribes the advanced device performance to the gradient-distributed donor-acceptor concentrations in the vertical direction. The findings provide guidelines for optimizing the morphology of the sequentially deposited top layer to achieve high-performance organic solar cells.

High-performance organic solar cells based on the inkjet-printed photoactive layer with efficiency approaching 16% are achieved by eliminating the “drying-line” dependent component inhomogeneity. The device of the disruptive pattern of 1 cm² gives a certificated efficiency of 12.18%.

Abstract

Inkjet printing (IJP) is a roll-to-roll (R2R) compatible fabrication method for large-area organic solar cells (OSCs). Unlike the coating process, the films are formed through droplet leveling and merging during IJP, and the pre-deposited droplets are partly dissolved by the subsequent droplets. Such a process yields undesired printing pattern lines, especially in large-area printed films. This study reveals that such a temperature-dependent “drying lines-related” phase separation morphology has caused component variation in the organic blend films, which leads to an obvious inhomogeneity of photocurrent in the printed OSCs. Such a phenomenon is attributed to the solubility difference between organic donor and acceptor molecules in the main printing solvent. A composite solvent strategy of ortho-dichlorobenzene (oDCB)/trimethylbenzene (TMB) and tetralin (THN) is developed to solve this problem. The introduction of THN suppresses the formation of printing drying lines during high-temperature printing due to the preferential miscibility of acceptor in THN, leading to the efficiency improvement to 13.96% and 15.78% for the binary and ternary devices. In addition, the 1 cm² device with a disruptive pattern gives an efficiency of 12.80% and a certificated efficiency of 12.18%.

Herein, a 4-amino-2,3,5,6-tetrafluorobenzoate cesium (ATFC) is developed as a bifacial defect passivator to tailor the perovskite/TiO₂ interface. The comprehensive experiments confirm that ATFC can passivate multiple defects, improve electrical properties, optimize energy band structure of TiO₂ layer, and synergistically passivate Pb-related defects at perovskite buried surface. Consequently, ATFC-modified γ-CsPbI₃ device achieves a remarkable efficiency of 21.11% and improved operational stability.

Abstract

The poor interface quality between cesium lead triiodide (CsPbI₃) perovskite and the electron transport layer limits the stability and efficiency of CsPbI₃ perovskite solar cells (PSCs). Herein, a 4-amino-2,3,5,6-tetrafluorobenzoate cesium (ATFC) is designed as a bifacial defect passivator to tailor the perovskite/TiO₂ interface. The comprehensive experiments demonstrate that ATFC can not only optimize the conductivity, electron mobility, and energy band structure of the TiO₂ layer by passivation of the undercoordinated Ti⁴⁺, oxygen vacancy (V _O), and free OH defects but also promote the yield of high-quality CsPbI₃ film by synergistic passivation of undercoordinated Pb²⁺ defects with the CO group and F atom, and limiting I⁻ migration via F···I interaction. Benefiting from the above interactions, the ATFC-modified CsPbI₃ device yields a champion power conversion efficiency (PCE) of 21.11% and an excellent open-circuit voltage (V _OC) of 1.24 V. Meanwhile, the optimized CsPbI₃ PSC maintains 92.74% of its initial efficiency after aging 800 h in air atmosphere, and has almost no efficiency attenuation after tracking at maximum power point for 350 h.

Due to the special molecular configuration of 3-amino-1-adamantanol (AAD), the bidirectional coordination with Ni³⁺ and Pb²⁺ enables AAD pre-buried interface modifier to be orderly arranged at the NiO_x/perovskite interface, which enhances the hole extraction, regulates ordered nucleation crystallization, and hinders the unfavorable reaction, effectively improving the photovoltaic and stability of inverted PSCs.

Abstract

The buried interface has important effect on carrier extraction and nonradiative recombination of perovksite solar cells (PSCs). Herein, to inactivate the buried interfacial defects of perovskite and boost the crystallization quality of perovskite film, 3-amino-1-adamantanol (AAD) serves as a pre-buried interface modifier on nickel oxide (NiO_x) surface to regulate the nucleation and crystallization process of perovskite precursor. The amino and hydroxyl groups in AAD molecule can synchronously coordinate with nickel ion (Ni³⁺) in NiO_x and lead ion in perovskite, respectively. The dual action favors the ordered arrangement of AAD molecules between NiO_x and perovskite, which not only enhances hole extraction in hole transport layer, but also provides active sites for homogeneous nucleation. Furthermore, AAD modifier blocks the unfavorable reaction between Ni³⁺ and perovskite, and effectively passivates the buried interfacial defects. The optimal inverted PSCs achieve a champion power conversion efficiency of 22.21% with negligible hysteresis, favorable thermal, optical, and long-term stability. Thus, this strategy of modulating perovskite nucleation and crystallization by pre-buried modifier is feasible for achieving efficient and stable inverted perovskite solar cells.

Almost all of the high efficiencies of all-polymer solar cells (all-PSCs) are obtained using chloroform as the solvent. Sequential processing and a ternary strategy are combined to enable the highest efficiency, 18.1%, for all-PSCs processed from an aromatic hydrocarbon solvent, which is also comparable to the highest value processed from chloroform.

Abstract

All-polymer solar cells (all-PSCs) have promising potential for industrial production due to their superior stability. Recently, the widespread application of the polymerized small molecule acceptor (PSMA) has led to a surge in the efficiency of all-PSCs. However, the high efficiencies of these devices generally rely on the use of the highly volatile solvent, chloroform (CF). Furthermore, the molecular weights of PSMA are lower than polymer donors, yet their crystallinity is weaker than typical small molecules, making most PSMA-based all-PSCs suffer from low electron mobility. To improve device performance and facilitate large scale production of all-PSCs, it is necessary to enhance electron mobility and avoid the use of CF. This paper investigates the use of sequential processing (SqP) for active layer preparation using toluene as the solvent to address these issues. This work reports 18.1% efficient all-PSC devices, which is the highest efficiency of all-PSCs prepared using non-halogen solvents. This work systematically compares the conventional blend-casting method with the SqP method using PM6 as the donor and PY-V-γ and PJ1-γ as the acceptors, and compares the performance of binary and ternary blends in both methods. Finally, this work measures the device stability and finds that SqP can significantly improve the photostability of the device.

Healing damage in halide perovskites (HaPs) is a fascinating property that can help extend the functional lifetime of devices. A novel approach is used to study mechanical damages and their recovery kinetics with atomic force microscopy operated in both ultra-high vacuum and controlled humidity conditions. Remarkably, this study observes that moderate humidity conditions aid healing in the HaPs.

Abstract

Recovery from damage in materials helps extend their useful lifetime and of devices that contain them. Given that the photodamages in HaP materials and based devices are shown to recover, the question arises if this also applies to mechanical damages, especially those that can occur at the nanometer scale, relevant also in view of efforts to develop flexible HaP-based devices. Here, this question is addressed by poking HaP single crystal surfaces with an atomic force microscope (AFM) tip under both ultra-high vacuum (UHV) and variably controlled ambient water vapor pressure conditions. Sequential in situ AFM scanning allowed real-time imaging of the morphological changes at the damaged sites. Using methylammonium (MA) and cesium (Cs) variants for A-site cations in lead bromide perovskites, the experiments show that nanomechanical damages on methylammonium lead bromide (MAPbBr₃) crystals heal an order of magnitude faster than Cs-based ones in UHV. However, surprisingly, under ≥40% RH conditions, cesium lead bromide (CsPbBr₃) shows MAPbBr₃-like fast healing kinetics. Direct evidence for ion solvation on CsPbBr₃ is presented, leading to the formation of a surface hydration layer. The results imply that moisture improves the ionic mobility of degradation components and leads to water-assisted improved healing, i.e., repair of nanomechanical damages in the HaPs.

Nature Photonics, Published online: 06 July 2023; doi:10.1038/s41566-023-01247-4

Nature Energy, Published online: 06 July 2023; doi:10.1038/s41560-023-01295-8

Publication date: October 2023

Source: Journal of Energy Chemistry, Volume 85

Author(s): Zhihao Li, Zhi Wan, Chunmei Jia, Meng Zhang, Meihe Zhang, Jiayi Xue, Jianghua Shen, Can Li, Chao Zhang, Zhen Li

Charge photogeneration from triplet excitons is demonstrated in an organic solar cell consisting of PM6, Y6, and PtTPBP as an electron donor, electron acceptor, and triplet sensitizer, respectively. Upon photoexcitation of PtTPBP, triplet excitons of Y6 are generated after triplet energy transfer from PtTPBP. The Y6 triplet excitons subsequently undergo endothermic charge separation at the PM6/Y6 interfaces.

Suppressing charge recombination is pivotal for further improving the power conversion efficiency of organic solar cells (OSCs). The bimolecular recombination of free charge carriers leads to the formation of both singlet and triplet charge transfer (CT) states at a ratio of 1:3 when considering simple spin statistics, meaning that charge recombination via the triplet excited state is the main deactivation channel for OSCs. Although the formation of local triplet excitons through back charge transfer from triplet CT states is thought to be a terminal loss process, it is shown that charge separation from triplet excitons can occur in nonfullerene acceptor (NFA)-based OSCs. To reveal the triplet exciton dynamics, a triplet sensitizer PtTPBP is doped into an OSC consisting of PM6 and Y6 as an electron donor and acceptor, respectively. Upon photoexcitation of PtTPBP, triplet excitons are formed, which subsequently transfer their energy to Y6, resulting in Y6 triplet excitons formation. Based on transient absorption and external quantum efficiency measurements, clear experimental evidence of charge photogeneration from Y6 triplet excitons at the PM6:Y6 interface is provided. This study highlights the importance of minimizing the energy difference between the singlet and triplet excited states of NFAs to suppress charge recombination.

Herein, light is shed on the inherent variability in solar cell fabrication by introducing a comprehensive opto-electronic-electric model. The model, calibrated using forty-eight distinct in-house fabricated cells, predicts four-terminal tandem solar cell performance considering fluctuating optical and recombination parameters with varied perovskite thickness. This paper concludes by unveiling potential efficiency improvements and the drawbacks of constant parameter models.

Opto-electronic models that seek to predict the performance of perovskite and tandem solar cells (PSCs/TSCs) often keep the optical and recombination parameters (ORPs) constant in subsequent studies. During fabrication of PSCs, however, these parameters can vary significantly. To account for the inherent fabrication variability, a comprehensive opto-electronic-electric model to predict the current–voltage characteristics of four-terminal (4T) TSCs is developed. This model is calibrated with forty-eight in-house fabricated transparent PSCs with perovskite layer thickness of 420, 550, and 700 nm and corresponding median efficiencies of 20.6%, 21.1%, and 21.0%, respectively; a CIS bottom cell with stand-alone efficiency of 17.5%; and combined 4T TSCs with a median efficiency of 29.0%. After fitting and validation, the functional forms of the ORPs are captured to estimate how they change with perovskite layer thickness. Finally, the errors with models assuming constant ORPs are demonstrated and how to improve the TSCs efficiency to more than 30% is discussed.

The efficiency of single-component organic solar cells based on Y6 is increased from 0.15% to 1.41% through interface regulation and mixed solvent strategy. This article elucidates the entropy-driven exciton separation mechanism by establishing a model of the dependence between molecular stacking and entropy and combining it with experimental data. Direct exciton separation mechanism is illustrated from experiment and theory aspects.

The excitons are generally decomposed into free charges by the heterojunction due to the low dielectric constant of organic materials. Recent research indicates that owing to the low exciton binding energy, the pure Y6 film can directly and spontaneously generate free charge carriers after photoexcitation, even without the assistance of the donor/acceptor interface driving force. However, the serious bimolecular recombination and trap-assisted recombination also limit the photovoltaic efficiency of single-component Y6 devices. Herein, efficient exciton separation and charge collection by changing the buffer layer and using mixed solvents to control the active layer morphology of single-component devices based on Y6 are achieved. It is found that the short-circuit current is significantly increased by properly adjusting the proportion of face-on and edge-on direction of molecules. Eventually, the power conversion efficiency (PCE) of single-component devices based on Y6 is increased from 0.15% to 1.41%. The corresponding dynamic process is revealed by ultrafast transient absorption spectroscopy and entropy effect on the exciton dissociation. Effective charge separation and collection in single-component devices is not only critical to improving the PCE, but provides an in-depth understanding for the further design of high-performance multicomponent devices.

Publication date: September 2023

Source: Nano Energy, Volume 114

Author(s): Yun Tang, Yuchao Zhang, Xinming Zhou, Ting Huang, Kai Shen, KangNing Zhang, Xiaoyan Du, Tingting Shi, Xiudi Xiao, Ning Li, Christoph J. Brabec, Yaohua Mai, Fei Guo

Publication date: 16 August 2023

Source: Joule, Volume 7, Issue 8

Author(s): Tian Du, Shudi Qiu, Xin Zhou, Vincent M. Le Corre, Mingjian Wu, Lirong Dong, Zijian Peng, Yicheng Zhao, Dongju Jang, Erdmann Spiecker, Christoph J. Brabec, Hans-Joachim Egelhaaf

This work summarizes the advances in morphology optimization in all-small-molecule organic solar cells from the viewpoint of efficient charge management and energy loss reduction, aiming to provide useful guidance in further materials design and device optimization and promote further development of all-small-molecule organic solar cells.

Abstract

All-small-molecule organic solar cells (ASM-OSCs) have received tremendous attention in recent decades because of their advantages over their polymer counterparts. These advantages include well-defined chemical structures, easy purification, and negligible batch-to-batch variation. Remarkable progress with a power conversion efficiency (PCE) of over 17% has recently been achieved with improved charge management (FF × J _SC) and reduced energy loss (E _loss). Morphology control is the key factor in the progress of ASM-OSCs, which remains a significant challenge because of the similarities in the molecular structures of the donors and acceptors. In this review, the effective strategies for charge management and/or E _loss reduction from the perspective of effective morphology control are summarized. The aim is to provide practical insights and guidance for material design and device optimization to promote further development of ASM-OSCs to a level where they can compete with or even surpass the efficiency of polymer solar cells.

Semitransparent organic photovoltaics combine the functions of photovoltaic conversion and visual semitransparency. The p-type polymers used in semitransparent organic photovoltaics are systematically summarized from the perspectives of chemical structures, conformation structures, and aggregation structures. The design guidelines for novel p-type polymers in high-performance semitransparent organic photovoltaics are also proposed.

Abstract

P-type polymers are polymeric semiconducting materials that conduct holes and have extensive applications in optoelectronics such as organic photovoltaics. Taking the advantage of intrinsic discontinuous light absorption of organic semiconductors, semitransparent organic photovoltaics (STOPVs) present compelling opportunities in various potential applications such as building-integrated photovoltaics, agrivoltaics, automobiles, and wearable electronics. The characteristics of p-type polymers, including optical, electronic, and morphological properties, determine the performance of STOPVs, and the requirements for p-type polymers differ between opaque organic photovoltaics and STOPVs. Hence, in this Minireview, recent advances of p-type polymers used in STOPVs are systematically summarized, with emphasis on the effects of chemical structures, conformation structures, and aggregation structures of p-type polymers on the performance of STOPVs. Furthermore, new design concepts and guidelines are also proposed for p-type polymers to facilitate the future development of high-performance STOPVs.

Nature Energy, Published online: 03 July 2023; doi:10.1038/s41560-023-01288-7

The solubility of FAPbI₃ halide perovskite always reaches the peak at moderate situations including medium solvent coordination ability, medium temperature, and medium FAI/PbI₂ molar ratio due to the interconversion between solute forms of solvent-containing lead complexes and solvated lead halide fragments in solution. Modulated dissolution affects crystallization paths and crystal quality when preparing single crystals, nanocrystals, and thin films.

The photovoltaic, luminescence, and detector fields have witnessed the robust application prospects of solution-processed halide perovskites. Deep insights into solution can pave the way toward the precise crystallization control of halide perovskites for giving full play to the advantages of those materials. Herein, the dissolution behavior of formamidinium lead iodide (FAPbI₃) together with lead iodide in amide solvents with regulated coordination ability at increasing temperature and under different molar ratio between formamidinium iodide (FAI) and PbI₂ is studied. The solvent coordination ability, temperature, and FAI/PbI₂ molar ratio demonstrate equivalent influence on the dissolution, and increasing those factors tends to increase the solubility first and decrease it then for Pb compounds. It is proposed that there are interchangeable Pb solute forms including solvent-containing lead complexes and solvated lead halide fragments in solution and the interconversion of both solutes driven by the above factors brings the solubility change. The modulated dissolution affects the crystallization behaviors of FAPbI₃ when preparing single crystals, nanocrystal dispersions, and thin films, and allows for regulated crystallinity in printable mesoscopic solar cells which demonstrate a power conversion efficiency of 18.40%.

Semitransparent perovskite solar cells are regulated by transparent electrodes and the perovskite absorber. The color semitransparent perovskite solar cells can be realized through optical management. If the semitransparent perovskite solar cells are applied to the glass curtain wall, it will bring aesthetics and generate photovoltaic power.

Semitransparent perovskite solar cells (ST-PSCs) are highly promising for application in building-integrating photovoltaics (BIPVs) due to their potential in tunable transparency and color. However, the comprehensive performance of ST-PSCs falls quite short of the ideal requirements for BIPV. Herein, more attention is to review how to balance transparency and power conversion efficiency for ST-PSCs. Optimizing transparent electrodes and the active layers are interesting strategies to achieve the transparency required by devices. In addition, to obtain color ST-PSCs, tuning the bandgap of perovskite layers and designing the optical structure of the electrode are effective strategies. Last but not least, three significant optical evaluation indexes of ST-PSCs are described in the supporting information: average visible transmittance, color rendering index, and light utilization efficiency.

A dual-interface modulation strategy is demonstrated using functional covalent organic frameworks to fabricate the high-performance perovskite solar cells; a champion efficiency of 24.26% is obtained together with enhanced long-term stability due to released tensile stress, reduced trap state density, as well as enhanced resistance of humidity and ultraviolet irradiation.

Abstract

Dual-interface modulation including buried interface as well as the top surface has recently been proven to be crucial for obtaining high photovoltaic performance in lead halide perovskite solar cells (PSCs). Herein, for the first time, the strategy of using functional covalent organic frameworks (COFs), namely HS-COFs for dual-interface modulation, is reported to further understand its intrinsic mechanisms in optimizing the bottom and top surfaces. Specifically, the buried HS-COFs layer can enhance the resistance against ultraviolet radiation, and more importantly, release the tensile strain, which is beneficial for enhancing device stability and improving the order of perovskite crystal growth. Furthermore, the detailed characterization results reveal that the HS-COFs on the top surface can effectively passivate the surface defects and suppress non-radiation recombination, as well as optimize the crystallization and growth of the perovskite film. Benefiting from the synergistic effects, the dual-interface modified devices deliver champion efficiencies of 24.26% and 21.30% for 0.0725 cm² and 1 cm²-sized devices, respectively. Moreover, they retain 88% and 84% of their initial efficiencies after aging for 2000 h under the ambient conditions (25 °C, relative humidity: 35–45%) and a nitrogen atmosphere with heating at 65 °C, respectively.

A re-assembling process is developed to overcome the charge confinement in perovskite nanocrystalline films (PeNCs) made of colloidal perovskite nanocrystals, by increasing the crystallite size and removing the long-chain ligands. Use of this strategy in gradient-bandgap PeNC solar cells achieves a high J _sc of 19.30 mA cm⁻² and a power conversion efficiency of 16.46%.

Abstract

The small nanoparticle size and long-chain ligands in colloidal metal halide perovskite quantum dots (PeQDs) cause charge confinement, which impedes exciton dissociation and carrier extraction in PeQD solar cells, so they have low short-circuit current density J _sc, which impedes further increases in their power conversion efficiency (PCE). Here, a re-assembling process (RP) is developed for perovskite nanocrystalline (PeNC) films made of colloidal perovskite nanocrystals to increase J _sc in PeNC solar cells. The RP of PeNC films increases their crystallite size and eliminates long-chain ligands, and thereby overcomes the charge confinement in PeNC films. These changes facilitate exciton dissociation and increase carrier extraction in PeNC solar cells. By use of this method, the gradient-bandgap PeNC solar cells achieve a J _sc = 19.30 mA cm⁻² without compromising the photovoltage, and yield a high PCE of 16.46% with negligible hysteresis and good stability. This work provides a new strategy to process PeNC films and pave the way for high performance PeNC optoelectronic devices.

Benzotriazole is introduced to donor–acceptor–acceptor configured small molecules for vacuum-deposited small-molecule organic solar cells (SMOSCs). Power conversion efficiencies (PCEs) in the range of 6.42–7.43% are attained for SMOSCs employing these small molecules as donors and C₇₀ as acceptors. Additionally, excellent performance in indoor photovoltaics with PCE of 14.84% is realized.

Three novel donor–acceptor–acceptor configured small molecules with benzotriazole as the central A building block are synthesized as donor materials for vacuum-deposited small-molecule organic solar cells (SMOSCs). The effects of different lengths of the side chains attached to the benzotriazole block on the molecular structure, electrochemical behavior, and optical properties of these donors are investigated systematically. Vacuum-deposited SMOSCs fabricated with these small molecule donors and C₇₀ as the acceptor exhibit power conversion efficiencies (PCEs) in the range of 6.42–7.43% under air mass 1.5 global (AM 1.5 G) 100 mW cm⁻² simulated solar illumination. Furthermore, the Me-DTDCPT-based devices deliver a promising PCE of 14.84% under 600 lux illumination by a fluorescent lamp, demonstrating its potential in indoor photovoltaic applications.

The semiconducting TAPC molecules can strongly interact with PbI₂ through π-Pb²⁺ interactions, thereby inhibiting excess PbI₂ aggregation and leaving a less n-type surface of the perovskite films. The perovskite solar cell based on TAPC-modified FA_0.95MA_0.05PbI_2.85Br_0.15 perovskite yields an improved efficiency of 23.15%, which is much higher than that of the control device of 21.19%.

Abstract

Excess lead iodide (PbI₂) aggregation at the charge carrier transport interface leads to energy loss and acts as unstable origins in perovskite solar cells (PSCs). Here, a strategy is reported to modulate the interfacial excess PbI₂ by introducing π-conjugated small-molecule semiconductors 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC) into perovskite films through an antisolvent addition method. The coordination of TAPC to PbI units through the electron-donating triphenylamine groups and π-Pb²⁺ interactions allows for a compact perovskite film with reduced excess PbI₂ aggregates. Besides, preferred energy level alignment is achieved due to the suppressed n-type doping effect at the hole transport layer (HTL) interfaces. As a result, the TAPC-modified PSC based on Cs_0.05(FA_0.85MA_0.15)_0.95Pb(I_0.85Br_0.15)₃ triple-cation perovskite achieved an improved PCE from 18.37% to 20.68% and retained ≈90% of the initial efficiency after 30 days of aging under ambient conditions. Moreover, the TAPC-modified device based on FA_0.95MA_0.05PbI_2.85Br_0.15 perovskite produced an improved efficiency of 23.15% compared to the control (21.19%). These results provide an effective strategy for improving the performance of PbI₂-rich PSCs.

Publication date: October 2023

Source: Journal of Energy Chemistry, Volume 85

Author(s): Jiayu You, Hongyu Bian, Meng Wang, Xinghong Cai, Chunmei Li, Guangdong Zhou, Hao Lu, Changxiang Fang, Jia Huang, Yanqing Yao, Cunyun Xu, Qunliang Song