Due to their unique features such as localized heat generation and spatiotemporal controllability, organic photothermal (OPT) films were explored using π-conjugated materials that exhibit high light absorption in the near-infrared region and tunability of molecular structures to achieve transparent to colorful OPT films. These OPT films showed a photothermal efficiency of 50 % to 95 % providing a thin film light absorber and a heating element. This talk reports on the preparation of OPT thin films and a mechanism on their photothermal heat generation with a demonstration of emerging applications including cell sheet harvesting, photo actuation, and energy harvesting.

Organic solar cells (OSCs) potentially can offer low cost, large area, flexible, light-weight, clean, and quiet alternative energy sources for indoor and outdoor applications. OSCs using non-fullerene acceptors (NFAs) have garnered a lot of attention during the past few years and shown dramatic increases in the power conversion efficiency (PCE) exceeding 19% for single-junction devices. In this talk, I will discuss the current progress and remaining challenges of solution-processed OSCs.

Over the past few decades, organic solar cells (OSCs) have made a significant progress, showing their great potential for low-cost, flexible, lightweight, portable and large-area energy-harvesting devices. In recent years, nonfullerene acceptors have emerged as a new candidate of n-type materials to overcome the disadvantages of fullerene derivatives in tuning optical and electronic properties. The strong and easily adjustable absorption characteristics of nonfullerene acceptors have been considered as a strong point compared to fullerene-type structures, showing a photovoltaic efficiency over ~19%. To further optimize the OSCs for next generation green energy sources, several important points need to be considered carefully. Here we discuss the fundamental correlations between molecular structure, exciton diffusion length, film morphology and device performance in new nonfullerene acceptor-based OSCs. In addition, perovskite solar cells (PeSCs) have also attracted extensive attention because of their inherent advantages such as solution processability, band-gap tunability, high absorption coefficient, and long carrier diffusion length. It has been successfully demonstrated that their power conversion efficiencies exceed 25%, which becomes similar with the highest PCE for crystalline Si solar cells. For PeSCs applications, appropriate charge transport layers (CTLs) are crucial for device performance and stability. The CTLs should have suitable energy levels for effective charge injection/transport while blocking opposite charges. Moreover, the CTL below the perovskite layer is critical because it significantly affects the crystal growth of the perovskite layer and its interfacial defects. In this presentation, a new series of conjugated polyelectrolytes is reported as an ideal interfacial layer and CTLs in PeSCs.

Charge-selective interlayers are crucial in thin-film photovoltaics, such as organic and perovskite solar cells (PSCs). Doped and undoped charge transport layers (CTLs) constitute perhaps the most important class of charge-selective interlayers; however, it is not well understood how a CTL should be designed in order to ensure efficient extraction of majority carriers while blocking minority carriers. This work clarifies how well CTLs with varying majority carrier conductivities block minority carriers. We use the charge extraction by linearly increasing voltage (CELIV) technique to determine the surface recombination velocity of minority carriers in model PSC devices with varying majority carrier conductivity in the transport layer [1]. Our results show that CTLs with high conductivity for majority carriers do not block minority carriers – at least not at operating voltages close to or above the built-in voltage – due to direct bimolecular recombination across the CTL/absorber interface. We furthermore discuss and propose design principles to achieve selective charge extraction in thin film solar cells using CTLs. Another important factor is the stabilizing effect of the PSC degradation through passivating the interface between CTLs and the perovskite absorber. We introduced a thin crosslinked PC61BM layer on top of the SnO2 electron transport layer, resulting in immobilization of Li+ ions. This resulted in the elimination of the “burn-in” degradation, showing for the first time a zero “burn-in” loss in the performances while boosting the device efficiency to > 22% for triple-cation based PSCs and > 24% for formamidinium based (FAPbI3) PSCs, proving the general validity of our approach and creating a new framework for the realization of stable PSCs devices [2]. [1] Mathias Nyman, Christian Ahläng, Staffan Dahlström, Manasi Pranav, Johannes Benduhn, Syeda Qudsia, Jan-Henrik Smått, Donato Spoltore, and Ronald Österbacka, submitted [2] Changzeng Ding, Li Yin, Jinlong Wang, Valentina Larini, Lianping Zhang, Rong Huang, Mathias Nyman, Liyi Zhao, Chun Zhao, Weishi Li, Qun Luo,Yanbin Shen, Ronald Österbacka, Giulia Grancini*, Chang-Qi Ma*, “Boosting Perovskite Solar Cells Efficiency and Stability: Interfacial Passivation of Crosslinked Fullerene Eliminates the “burn-in” Decay”, Advanced Materials 35, 2207656 (2023)

Organic–inorganic halide perovskites have demonstrated tremendous potential for next-generation electronic and optoelectronic devices due to their remarkable carrier dynamics. Current studies are mostly focused on polycrystals, since controlled growth of high-quality single crystals is challenging. In this presentation, I will discuss strategies that enabled the first chemical epitaxial growth of single-crystal hybrid halide perovskites. Using advanced microfabrication, homo-/hetero-epitaxy, and a low-temperature solution method, single crystals can be grown with controlled locations, morphologies, orientations, and strain levels. By a lifting off approach, single-crystal thin films can be transferred from the epitaxial substrate to a general flexible substrate. Extending this strategy to low-dimensional perovskites yields nanostructured superlattices, based on which a solar cell with an open-circuit voltage exceeding the Shockley-Queisser limit is demonstrated. This approach opens up broad opportunities for hybrid halide perovskite materials based flexible high-performance electronic and optoelectronic devices.

The most stable and efficient perovskite solar cells reported so far, have mostly been prepared by solution-processing. This is due in part to the technical difficulties associated with the vacuum deposition from individual thermal sources. Here we present multi-component materials obtained by using multiple sources (up to 4) thermal vacuum deposition. Different stoichiometries are evaluated, varying the A-site cations, as well as mixed halide systems. Both narrow bandgap and wide bandgap materials will be presented, with bandgap spanning from 1.5 to 1.8 eV. We highlight the importance of the control over the film morphology and composition, which differs substantially when these compounds are vacuum processed. We identify thermally stable compositions and apply them to opaque and bifacial perovskite solar cells. Avenues to improve the material stability and to maximize the open circuit voltage using additives and/or novel charge transport layers will also be discussed.

Perovskite solar cells promise to yield efficiencies beyond 30% by further improving the quality of the materials and devices. Electronic defect passivation, and suppression of detrimental charge-carrier recombination at the different device interfaces has been used as a strategy to achieve high performance perovskite solar cells. In this presentation, I will discuss the role of electronic defects and how these can be passivated to improve charge-carrier lifetimes and to achieve high open-circuit voltages. I will discuss the characterization of 2D and 3D defects, such as grain boundaries, crystal surface defects, and precipitate formation within the films, by synchrotron-based techniques. The importance of interfaces and their contribution to detrimental recombination will also be discussed. As a result of these contributions to better understanding 2D and 3D defects, the perovskite solar cell field has been able to improve device performance. Albeit the rapid improvements in performance, there is still a need to improve these defects to push these solar cells beyond the current state-of-the-art.

The overall efficiency of organic photovoltaic devices has made impressive progress in recent years, but often active materials now require complex, multi-step synthesis, potentially limiting their application. We report approaches to prepare building blocks in just one or two steps, allowing the preparation of conjugated polymers of low synthetic complexity which can be readily upscaled. I will highlight how this approach can be used to readily build libraries of conjugated polymers to more rapidly identify promising materials for application in OPV and OECT devices. Finally approaches to introduce additional functionality via post-polymerisation backbone modification will be discussed.

In recent years, hairy rod semiconducting polymers have risen to the forefront of organic electronic implementations for, among other factors, their desirable photophysical properties. Departing from conventional semiflexible polymers, the newer generation of materials have increased backbone rigidity. This evokes the question of how increasing rigidity manifests in the photophysical response of these materials. Herein, we use solid-state vacuum compression molding to induce elusive liquid crystallinity in quintessential thermotropic Poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene], PBTTT. By means of conventional and fast calorimetry, we elucidate the changes in phase behavior of solution processed PBTTT upon solid-state compression. Furthermore, anisotropy, associated with liquid crystallinity, is observed through transmission X-ray scattering. The shift towards increased anisotropy strongly influences the photophysical aggregation of transition dipole moments as it determines the local ordering of chromophores. We probe the optical response as a function of temperature to determine dominant aggregation states and further exemplify local ordering. This work provides a framework for controlling photophysical response in thermotropic or liquid crystalline-like polymer semiconductors by means of processing.

Organic semiconductors have garnered interest in wide range of applications including photovoltaics, light emission, photodetectors, sensors, and photocatalysis. Specifically, the emerging organic photovoltaics (OPVs) make use of donor-acceptor conjugated polymers in a bulk heterojunction (BHJ) morphology. Focused continued efforts in developing donor polymers and non-fullerene acceptors enabled the power conversion efficiency (PCEs) of single-junction solar cells over 19% today.[1,2] With the aim of further improving PCEs and stability of OPVs, efforts have been expended on understanding structure-processing-stability-property interrelations, which necessitates molecular-level understanding of thin film morphology of the photoactive layer, contact layers and interfaces between them. Here we provide a method to resolve structure-property relationships in OPVs using multiscale characterization and device physics including charge generation, extraction and recombination processes.[3] Synergism between the X-ray diffraction, solid-state NMR/EPR and modelling techniques enabled the bulk and interfacial morphology in BHJ thin films and contact layers to be resolved and distinguished.[3,4] We will discuss the state-of-the-art 2D NMR and EPR spectroscopy and imaging techniques suitable for resolving thin film morphology in PM6:Y6 solar cells at atomic-scale resolution. In addition, we will demonstrate how a hybrid bottom-up and top-down NMR crystallography approach in conjunction with device physics can be used to establish structure-property relationships in NFA based OPVs.[4,5] Our approach can be further extended to resolve structure-stability-property relationships in high performance organic photodetectors (OPDs) and organic electrochemical transistors (OECTs). References: 1. L. Zhu, M. Zhang, J. Xu, C. Li, J. Yan, G. Zhou, W. Zhong, T. Hao, J. Song, X. Xue, Z. Zhou, R. Zeng, H. Zhu, C.-C. Chen, R.C. I. MacKenzie, Y. Zou, J. Nelson, Y. Zhang, Y. Sun, F. Liu, Single-junction organic solar cells with over 19% efficiency enabled by a refined double-fibril network morphology. Nature Materials 2022, 21 (6), 656-66. 2. Y. Cui, Y. Xu, H. Yao, P. Bi, L. Hong, J. Zhang, Y. Zu, T. Zhang, J. Qin, J. Ren, Z. Chen, C. He, X. Hao, Z. Wei, J. Hou, Single-Junction Organic Photovoltaic Cell with 19% Efficiency. Adv. Mater. 2021, 33, 2102420. 3. B. R. Luginbuhl, P. Raval, T. Pawlak, Z. Du, T. Wang, G. Kupgan, N. Schopp, S. Chae, S. Yoon, A. Yi, H. J. Kim, V. Coropceanu, J.-L. Brédas, T.-Q. Nguyen, G. N. M. Reddy, Resolving Atomic-Scale Interactions in Nonfullerene Acceptor Organic Solar Cells with Solid-State NMR Spectroscopy, Crystallographic Modelling, and Molecular Dynamics Simulations. Adv. Mater. 2022, 34, 2105943. 4. A. Karki, J. Vollbrecht, A. J. Gillett, S. S. Xiao, Y. Yang, Z. Peng, N. Schopp, A. L. Dixon, S. Yoon, M. Schrock, H. Ade, G. N. M. Reddy, R. H. Friend, T.-Q. Nguyen, The role of bulk and interfacial morphology in charge generation, recombination, and extraction in non-fullerene acceptor organic solar cells, Energy Environ. Sci. 2020, 13, 3679. 5. A. L. Dixon, H. Vezin, T.-Q Nguyen, G. N. M. Reddy, Structural insights into Lewis acid and F4TCNQ doped conjugated polymers by solid-state magnetic resonance spectroscopy. Materials Horizons, 2022, 9, 981-990.

Non-radiative recombination loss (Eloss,nr or ΔE3) suppression and performance boosting are in the center of OSCs research. Herein, we developed a novel non-monotonic intermediate state manipulation (NM-ISM) strategy for state-of-the-art NFA OSCs by employing 1,3,5-trichlorobenzene (TCB) as crystallization regulator, which optimizes the film crystallization process, regulates the self-organization of bulk-heterojunction (BHJ) in a non-monotonic manner, i.e., first enhancing and then relaxing the molecular aggregation. As a result, we have achieved efficient OSCs with reduced Eloss,nr. In PM6:BTP-eC9 OSC system, the ISM strategy successfully offers a record binary OSC PCE of 19.31% (18.93% certified) with very low Eloss,nr of 0.190 eV. Nature Communicaitons, in press

Characterization of organic photodiodes (OPDs) requires experimental measurement of the OPD dark noise, devoid of shot-noise assumption. Importantly, the associated noise measurement bandwidth is highly relevant for determining the linear dynamic range (LDR), noise equivalent power (NEP), and specific detectivity (D*). In this work, different OPDs are experimentally studied for their dark characteristics. Different measurement bandwidths associated with the time-dependent dark current are investigated. The apposite bandwidth is counter-checked for its relationship between the noise power density spectrum and the experimentally measured noise. The resultant standardized approach is then used to provide correct reporting of NEP, LDR, and D*.

The IoT will result in deployment of billions of devices requiring local power. For the indoor environment, ambient light harvesting is a tangible strategy which could reduce reliance on batteries and provide ‘set-and-forget’ functionality. Organic Photovoltaics is emerging as a lead technology for indoor PV due to a number of factors including low intensity performance, tuneable absorption, and flexible form factors. In my talk I will examine the thermodynamics and electro-optics of organic PV for the indoor environment. I will advance a model to predict the performance and analyse current high efficiency OPV systems designed for outdoor AM1.5G solar harvesting.

We designed and fabricated highly reflective polymer-based chirped mirrors for thermal management using a titanium oxide hydrate/poly(vinyl alcohol) hybrid as the high-refractive-index material and a commodity polymer as the low-refractive-index material. Typically, chirped reflectors are fabricated using inorganic dielectrics incompatible with large-area and flexible applications. All-organic alternatives suffer from a small refractive index contrast between layers, limiting reflectivity. By employing this inorganic/organic hybrid material with a tunable refractive index (1.5-2.1), we accomplish a large enough refractive index contrast with commodity polymers and contribute towards making these photonic structures more readily accessible for heat management purposes.

Deposition methods have been used extensively to achieve high-quality, semi-transparent solar cells. Here, we have studied semi-transparent electrodes based on WO3 and Ag, to boost the PCE in semi-transparent formamidinium lead bromide (FAPbBr3) solar cells. A screening upon the mixed halide perovskite, from pure bromide to pure iodide has been made, demonstrating that the PCE increase with the semi-transparent electrode compare to the conventional semi-transparent Au. This work demonstrates the potential use of semi-transparent electrode to improve the light harvesting of the perovskite layer, by using optical methods to compensate chemical limitation, paving the way for application in building integration.

Perovskite materials, most notably organo-lead iodide species, have recently demonstrated great potential in future high-performance photovoltaics. Formamidinium lead iodide perovskite (FAPbI3) features desirable bandgap and thermal resistance, and has thus emerged as the most promising candidate among the perovskite family for highly efficient photovoltaic devices. However, the photoactive black-phase FAPbI3 is not energetically favorable at room temperature. Polytype formation and other intermediate non-photoactive phases can readily occur, which undermines the photovoltaic performance. Through multimodal in-situ monitoring of the perovskite crystallization process, we found an oriented nucleation mechanism that acted as the key to avoid undesirable phases. This concept was applicable to improving the photovoltaic device performance under different film-processing scenarios. In this talk, I will present our recent progress on improving the stablity and efficiency of FA-based perovskites, and the potential of the commercialization will be discussed.

Driven by the development of non-fullerene electron acceptor materials, the performance of organic solar cells (OSCs) has recently shown a remarkable improvement, with power conversion efficiencies nearly doubling from 11% to 19% in less than 10 years. However, the efficiency of OSCs is still lower than inorganic technologies, where efficiencies of >20% are commonplace. This is primarily due to excessive non-radiative recombination in OSCs, which reduces the open circuit voltage from the radiative limit. In our work, we have identified recombination via low energy triplet excitons as a key factor responsible for the large non-radiative losses in OSCs. In state-of-the-art systems, such as ‘PM6:Y6’, up to 90% of the charge carrier recombination proceeds via triplet exciton states; this reduces the open circuit voltage by up to 60 mV. To address this issue, we propose two viable strategies. First, through the identification of systems where recombination via triplet excitons is suppressed, we demonstrate that significant hybridisation of the molecular triplet exciton and triplet charge transfer state can disfavour terminal recombination into the former. Second, we show that triplet-triplet annihilation has the potential to mitigate against triplet exciton losses by recycling up to half of these states formed back into singlet excitons, providing an opportunity for radiative recombination to occur. Therefore, our findings constitute a framework to alleviate non-radiative losses via triplet excitons in OSCs, which could further reduce the performance gap between organic and inorganic solar cell technologies.

Over the past six years, the solar power conversion efficiencies of organic solar cells (OSC) have greatly improved from 12% to 19%, closing the gap with inorganic and hybrid solar cells. The major breakthrough behind the rapid efficiency improvement is the development of non-fullerene acceptor molecules, replacing the traditional fullerene molecules as electron-accepting materials. Understanding the photophysical processes underlying these high-performance materials is crucial to OSC research. In this talk, I will present transient optical spectroscopy results on non-fullerene OSC blends with small interfacial energy offsets. By optically probing the time evolution of excited states, we show that free charges are generated via thermal activation of interfacial charge-transfer (CT) states on a hundred picosecond timescale. Reduced charge separation rate is observed at lower temperatures, leading to increasing charge recombination either directly at the donor-acceptor interface or via the emissive singlet exciton state. A kinetic model is used to rationalize the results, showing that although photogenerated charges have to overcome a significant Coulomb potential to generate free carriers, OSC blends can achieve high photocurrent generation yields even at reduced temperatures given that the thermal dissociation rate of charges outcompetes the recombination rate.

Modest exciton diffusion lengths dictate the need for nanostructured bulk heterojunctions in organic photovoltaic (OPV) cells, however, this morphology compromises charge collection. Here, we reveal rapid exciton diffusion in films of high performing fused-ring non-fullerene acceptors. Using experimental and computational approaches, rapid exciton diffusion is shown to arise from intrinsic molecular and packing factors and can even now be screened computationally. Relieving exciton diffusion constraints has important implications for OPVs; large, ordered, and pure domains – even bilayer architectures – enhance charge separation and transport, and suppress recombination, thereby boosting fill factors.

Organic photovoltaic cells (OPVs) using Y-series nonfullerene electron acceptors (NFA) have recently achieved record high efficiencies. However, there is still lack of experimental investigation on how individual molecules and different aggregates of these NFAs contribute to the overall charge transfer (CT) properties. We fabricated solid-solution thin films by dispersing Y-series NFA molecules in insulating polymers at various loading ratios and the CT property has been investigated using electroabsorption (EA) spectroscopy. This study provides direct experimental evidence on the origin of the strong CT character in thin film and brings insight into the correlation between charge transfer and delocalization of wavefunction.

Organic electronic materials possess unique opto-electronic and processing properties that provide broad opportunities for use in light-emitting diodes, solar-energy harvesting systems, to next-generation sensors and neuromophic computing components. These technologies have been continually improving over the past decades, aided by advancements in materials chemistry and processing innovation. State-of-the-art polymer semiconductors typically have an electron donor-acceptor (D-A) backbone structure with a number of fused ring moieties, and complex aliphatic or, e.g., ethylene-oxide side chains that decorate the backbone to provide solubility. It is important to recognize that the physical properties of the side chains are substantially different from the backbone, constituting an amphiphilic-like characteristics transverse to the backbone reminiscent of phospholipid and surfactant molecular analogs, and simple classical descriptions of amorphous vs. semicrystalline structure no longer apply. Here, we discuss how the FSC technique can be used for the identification of thermodynamic transitions of next generation D-A polymers commonly used in the organic solar cell area to obtain important structural information of this new class of materials and, in turn, establish processing guidelines towards materials of specific optical or electrical characteristics, and improved materials design for organic optoelectronic devices.

Formamidine (FA)-based perovskite has bandgap close to the optimal bandgap of single junction solar cell is gradually attracting more attentions in the community. However, cracks are commonly found in FA-based perovskite films right after the spin-coating at room temperature, which has detrimental effect on the solar cell performance. Cooling down the glovebox temperature has become a general practice to solve this issue, yet the temperature effect on the nucleation and crystallization processes if still unknow. In this work, we developed in-situ photoluminescence and absorption techniques to investigate the temperature effect on the nucleation and crystallization of FA-based perovskite crystals (FAxMA1-xPbI3) during spin-coating and annealing processes. Combining with density functional theory (DFT) results, we have found that FAPbI3 framework is firstly generated, which is then followed by the incorporation of FA, MA, Pb, I ions into crystal lattice. Both the higher FA content and higher temperature would significantly increase the growth rate of perovskite, resulting in phase aggregation and stress relief. Leading to the formation of cracks. This work provides a unique and intuitive perspective towards the understanding of the FA-based perovskite growth mechanism.

Controlling the crystallization to achieve a high-quality homogeneous film of mixed halide wide bandgap (>1.7 eV) perovskites is vital for the development of tandem and semitransparent solar cells. Since nucleation from the precursor ions is sensitive and typically completed in a few seconds, monitoring the crystallization during the perovskite film formation is still challenging. Here, we demonstrate an in-situ dynamic optical-probing technique which can monitor the crystallization without affecting the process by laser excitation. It is found that the generally observed low film quality is due to the inefficient nucleation of MAPbI2Br during the spin-coating process. Once the film is transferred to the annealing process, we find that there is a fast ion-exchange of halide ions within the first few second, and large amount of PbI2 is formed simultaneously which strongly deteriorate the film homogeneity. We find that an additional preheating process at a moderate temperature is crucial to promote the nucleation of perovskite and retard the forming of PbI2. Such process can significantly increase the number of MAPbI2Br nuclei, and therefore facilitates the formation of uniformly composited perovskite film. Eventually, only a small amount of PbI2 is observed around the grain boundary which in turn passivates the perovskite. This presentation would provide insight into identifying the limiting factors which could affect the crystallization of the organo-metal halide perovskites films during the fabrication processes by in-situ optical techniques.

We studied CsFAMAPbBrI mixed perovskite solar cells with an ultrafast time-resolved transient absorption (TA) spectroscopy using pump-probe setup based on a femtosecond Ti:sapphire laser system(36 fs pulses centered at 805 nm, 1 kHz repetition rate). Frequency-doubled and supercontinuum lights were used as pump and probe beams, respectively. Our study presents a spectroscopic analysis of the dynamics of photo-induced charge carrier generation and decay in perovskite solar cells. We conducted a comparative study on perovskite solar cell devices with/without passivation layer, under various excitation pump intensities, and in a series of atmospheric exposures.

The large non-radiative recombination is the main factor that limits organic solar cells (OSCs). In this work, we synthetized two novel structurally similar oligomers high-performance ternary OSCs with low energy loss. As third components, these PM6 analogue oligomers effectively suppress the non-radiative recombination of the ternary OSCs, the oligomers showed ultra-high EQEEL of 0.05% and improved VOC was achieved in ternary OSCs. Moreover, the different compatibility of 5BDTBDD and 5BDDBDT with PM6 and BTP-BO4Cl fine-tunes the morphology of the active layer. This is the first work that demonstrates novel structurally compatible D-A type oligomers are effective third components, and provides new understanding of energy loss mechanisms towards high performance OSCs.

Organic solar cells (OSCs) have attracted research interest by their elastic character for wearable and stretchable devices. Especially all-polymer OSCs with same composition unit between donor and acceptor are enhanced their thermal stability and mechanical robustness. However, in most of OSCs, high elasticity often reduces the power conversion efficiency (PCE) by low charge transfer be cacused by weak aggregation of each donor and acceptor composite. In this study, new polymer acceptors consisted by the poly siloxane-spacer (PSS) with benzoditohiophene (BDT) and Y6 non-fullerene small molecule acceptor (NFSMA) derivative are synthesized and characterized for high performance and highly stretchable OSCs. The PSS unit has intrinsically stretchable property due to their rubber like structure, therefore introducing PSS unit as a building block in the OSC polymers suggests improve its own elasticity of the OSC polymers. In addition, introducing PSS unit increase solubility of OSC polymers, enabling high performance OSC by solution process using a non-halogenated green solvents. For example, all-polymer OSCs based on PSS containing polymer achieved more high PCE value (13.5 %) and crock-onset strain (COS = 15.2 %) than non-containing one (PCE = 9.8% and COS = 9.6%)

Although it has been clearly elucidated that the change in the overall bulk-heterojunction (BHJ) morphology of PM6:Y6 induced by the difference in solvents results in a variation in the performance of the entire solar cell, the charge dynamics during the charge separation process induced by morphological changes have not yet been deeply studied. Based on mobility and photocurrent-related studies, it has been inferred that holes are deeply involved in these charge generation and separation processes. The decrease in exciton dissociation probability observed in the PM6:Y6 solar cell fabricated using CB (PM6:Y6-CB) was found to be due to the change in the hole transfer state caused by morphological changes. For the PM6:Y6 solar cell fabricated using CF (PM6:Y6-CF), it was determined that the density of the state (DOS) of the effective hole transfer state (hECT) was small, as hECT and Y6 HOMO were almost degenerate, and the lower hECT, which can interfere with hole transfer, was also formed minimally. However, for PM6:Y6-CB, the overlapping region of hECT and the highest occupied molecular orbital (HOMO) of Y6 shifted towards the lower energy side (upper hECT), and a lower effective hECT that can act as a defect was significantly formed. These facts obtained by EL deconvolution were clearly confirmed in time-resolved photoinduced absorption spectroscopy. As a result, it is concluded that the decrease in fill factor (FF) and current density (JSC) in PM6:Y6-CB is due to the degradation of hole transfer from Y6 HOMO to PM6 HOMO. This analysis shows that the morphological changes in non-fullerene acceptor (NFA) solar cells affect the formation of hole transfer levels, which in turn affect the charge separation efficiency.