Chen Weijie

A photocatalyst with Cu single atoms anchored on S doped polymeric carbon nitride (p-CN) is designed for photo-oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran under visible-light irradiation. The construction of dual atomic sites of Cu–N₄ and C–S–C in Cu SAs/p-CNS facilitates the separation of photo-generated carriers and thus enhances the photo catalytic activity.

Abstract

The separation efficiency of photo-generated carriers is still a great challenge that restricts the practical application of photocatalytic technology. The design of spatial separation path for photo-generated carriers at atomic level provides an innovative approach to address this challenge. Herein, a facile dual atomic sites strategy, consisting of Cu-N₄ and C-S-C active moieties decorated on polymeric carbon nitride (Cu SAs/p-CNS) is reported to simultaneously achieve the highly efficient separation of photo-generated electrons and holes for boosting photocatalytic performance. As a proof of concept, the Cu SAs/p-CNS is successfully applied to the photo-oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF), which exhibits 77.1% HMF conversion and 85.6% DFF selectivity under visible light irradiation. The activity is considerably higher than that of bulk p-CN, S doped p-CN, and p-CN supported Cu single atom catalysts. Theoretical calculations and experimental results suggest that, during photocatalytic reaction, the isolated Cu-N₄ sites directly capture photo-generated electrons, while the surrounding S atoms bear photo-generated holes, which synergistically facilitates the separation of photo-generated carriers and thus results in enhanced photocatalytic activity. This study provides a new perspective for the rational design of high performance photocatalysts at atomic level.

The baseplate temperature-dependent blend morphology of sequential deposition-processed organic solar cells at vertical and lateral scales is systematically studied, and the temperature-microstructure-performance relationship is established.

Abstract

Numerous previous reports on the sequential deposition (SD) technique have demonstrated that this approach can achieve a p-i-n active layer architecture with an ideal vertical composition gradient, which is one of the critical factors that can influence the physical processes that determine the photovoltaic performance of organic solar cells. Herein, a commonly used photovoltaic system comprised of PM6 as a donor and Y6 as an acceptor is investigated with respect to sequential blade-processing deposition to comprehensively explore the morphology characteristics as a function of baseplate temperature. A systematic study of the temperature-dependent blend morphology elucidates the SD-processed configuration merits and device physics behind temperature-controlled degree of vertical composition gradient, and constructs the temperature-microstructure-property relationship for the corresponding photovoltaic parameters. The result shows, as the temperature increases, the morphology of the active layer has undergone a distinct evolution from the pseudo-bulk heterojunction to a pseudo-planar heterojunction and then to a pseudo-planar bilayer, leading to a non-monotonic correlation between baseplate temperature and device performance. This investigation not only reveals the importance of precisely controlling baseplate temperature for gaining vertical morphology control, but also provides a path toward rational optimization of device performance in the lab-to-fab transition.

Three nonfused ring electron acceptors (NFREAs) with different π-conjugation length are designed and synthesized. The π-conjugation length can significantly influence the molar extinction coefficient and the electron mobility. The first 3D network packing is observed for 2BTh-2F. 2BTh-2F derivative based organic solar cells give a high power conversion efficiency of 15.44%, which is the highest value reported based on NFREAs.

Abstract

Three nonfused ring electron acceptors (NFREAs; 2Th-2F, BTh-Th-2F, and 2BTh-2F) with thieno[3,2-b]thiophene bearing two bis(4-butylphenyl)amino substituents as the core, 3-octylthiophene or 3-octylthieno[3,2-b]thiophene as the spacer, and 3-(1,1-dicyanomethylene)-5,6-difluoro-1-indanone as the terminal group are designed and synthesized. The molar extinction coefficient of acceptors and the electron mobility of blend films gradually increase with increasing π-conjugation length. Moreover, 2BTh-2F displays a planar molecular conformation assisted by S···N and S···O intramolecular interactions. More importantly, the molecular stacking changes from 2D packing for the 2Th-2F analog to 3D network packing for 2BTh-2F. Due to these comprehensive merits, 2BTh-2F:PBDB-T-based organic solar cells give a high power conversion efficiency of 14.53%. More impressively, when D18 is used as the donor polymer, the power conversion efficiency is further enhanced to 15.44%, which is the highest value reported for solar cells based on NFREAs.

The efficiency of polycrystalline perovskite solar cells is approaching that of silicon, while being substantially higher than that of monocrystalline perovskite despite the optoelectronic properties following the opposite trend. This review questions the future of perovskite single crystals and proposes new strategies that unleash their full potential to achieve record solar cells.

Abstract

Lead halide perovskite solar cells have been gaining more and more interest. In only a decade, huge research efforts from interdisciplinary communities enabled enormous scientific advances that rapidly led to energy conversion efficiency near that of record silicon solar cells, at an unprecedented pace. However, while for most materials the best solar cells were achieved with single crystals (SC), for perovskite the best cells have been so far achieved with polycrystalline (PC) thin films, despite the optoelectronic properties of perovskite SC are undoubtedly superior. Here, by taking as example monocrystalline methylammonium lead halide, the authors elaborate the literature from material synthesis and characterization to device fabrication and testing, to provide with plausible explanations for the relatively low efficiency, despite the superior optoelectronics performance. In particular, the authors focus on how solar cell performance is affected by anisotropy, crystal orientation, surface termination, interfaces, and device architecture. It is argued that, to unleash the full potential of monocrystalline perovskite, a holistic approach is needed in the design of next-generation device architecture. This would unquestionably lead to power conversion efficiency higher than those of PC perovskites and silicon solar cells, with tremendous impact on the swift deployment of renewable energy on a large scale.

An extended π-conjugated organic spacer, namely TTDMAI, is successfully developed as spacers for 2D Dion–Jacobson perovskites. A champion efficiency of 18.82% is demonstrated due to the improved film quality and preferred crystal vertical orientation thanks to the templated grain growth by the large crystal nuclei size in the precursor solution.

Abstract

2D Dion–Jacobson (DJ) perovskites have become an emerging photovoltaic material with excellent structure and environmental stability due to their lacking van der Waals gaps relative to 2D Ruddlesden–Popper perovskites. Here, a fused-thiophene-based spacer, namely TTDMAI, is successfully developed for 2D DJ perovskite solar cells. It is found that the DJ perovskite using TTDMA spacer with extended π-conjugation length exhibits high film quality, large crystal size and preferred crystal vertical orientation induced by the large crystal nuclei in precursor solution, resulting in lower trap density, reduced exciton binding energy and oriented charge transport. As a result, the optimized 2D DJ perovskite device based on TTDMA (nominal n = 4) delivers a champion PCE up to 18.82%. Importantly, the unencapsulated device based on TTDMA can sustain average 99% of their original efficiency after being stored in N₂ for 4400 h (over 6 months). Moreover, light, thermal, environmental and operational stabilities are also significantly improved in comparison with their 3D counterparts.

Pure formamidinum (FA)-based 2D perovskite solar cells (PSCs) achieve a record power conversion efficiency (PCE) of 21.07% (certified over 20%), the highest efficiency for low-dimensional PSCs (n ≤ 10) reported to date, together with the improved device stability. The high-efficiency device exhibits a narrowed bandgap and unique 2D–3D intermixing phase distribution for improved light absorption and superior charge transport.

Abstract

Owing to their insufficient light absorption and charge transport, 2D Ruddlesden–Popper (RP) perovskites show relatively low efficiency. In this work, methylammonium (MA), formamidinum (FA), and FA/MA mixed 2D perovskite solar cells (PSCs) are fabricated. Incorporating FA cations extends the absorption range and enhances the light absorption. Optical spectroscopy shows that FA cations substantially increase the portion of 3D-like phase to 2D phases, and X-ray diffraction (XRD) studies reveal that FA-based 2D perovskite possesses an oblique crystal orientation. Nevertheless, the ultrafast interphase charge transfer results in an extremely long carrier-diffusion length (≈1.98 µm). Also, chloride additives effectively suppress the yellow δ-phase formation of pure FA-based 2D PSCs. As a result, both FA/MA mixed and pure FA-based 2D PSCs exhibit a greatly enhanced power conversion efficiency (PCE) over 20%. Specifically, the pure FA-based 2D PSCs achieve a record PCE of 21.07% (certified at 20%), which is the highest efficiency for low-dimensional PSCs (n ≤ 10) reported to date. Importantly, the FA-based 2D PSCs retain 97% of their initial efficiency at 85 °C persistent heating after 1500 h. The results unambiguously demonstrate that pure-FA-based 2D PSCs are promising for achieving comparable efficiency to 3D perovskites, along with a better device stability.

Herein, Sr-doped CsPbI₃ quantum dots (QDs) as an interfacial layer for CsPbIBr₂ solar cells are introduced. The simultaneous Sr²⁺ ion doping and surface Cl⁻ ion passivation for CsPbI₃ QDs results in an enhanced photoluminescence quantum yield with an increased carrier lifetime. The resulting CsPbIBr₂ solar cells achieve a highly efficient power conversion efficiency of 10.32%.

Interfacial recombination and nonradiative recombination in inorganic CsPbIBr₂ solar cells impede the device performance. Herein, surface passivation of CsPbIBr₂ inorganic perovskite layers with Sr-doped CsPbI₃ quantum dots (QDs), which act as an efficient interlayer to reduce interfacial recombination and enhance hole extraction as well, is reported for the first time. It is found that the simultaneous Sr²⁺ ion doping and surface Cl⁻ ion passivation for CsPbI₃ QDs results in an enhanced photoluminescence quantum yield with an increased carrier lifetime. The resulting perovskite solar cells achieve a highly efficient power conversion efficiency of 10.32% with enhanced high open circuit V _oc of 1.20 V. It is logically inferred that this approach can be a promising tool for improving device performance in inorganic perovskite solar cells.

Super flexible p–i–n-type transparent conducting oxide (TCO)-free perovskite solar cells are demonstrated on lithium bis(trifluoromethane) sulfonimide (Li-TFSI)-doped graphene electrodes on polydimethylsiloxane substrates. Li-TFSI increases the single-layered graphene conductivity while codoping the poly(triarylamine) hole-transporting layer. The resulting flexible TCO-free perovskite solar cells produce a best power conversion efficiency of 19.01% and show excellent bending and long-term photostability.

Highly efficient organic–inorganic hybrid perovskite solar cells (OIHP-SCs) are often fabricated on a transparent conducting oxide (TCO) substrate such as indium tin oxide (ITO). However, the presence of TCOs is disadvantageous to the development of flexible OIHP-SCs due to the brittle nature of ITO which is easily breakable during bending. Herein, a flexible TCO-free OIHP-SC is demonstrated by using lithium bis(trifluoromethane)sulfonimide (Li-TFSI) as a codopant for the single-layer graphene transparent conducting electrode and poly(triarylamine) hole-transporting material (HTM) on a flexible polydimethylsiloxane substrate. The optical and electrical properties of the Li-TFSI-doped graphene substrate are measured by controlling the doping amount and the best conditions for charge extraction are established at a doping concentration of 20 mm Li-TFSI, thus optimizing the device photovoltaic performance. As a result, a highest power conversion efficiency of 19.01% is demonstrated by the flexible TCO-free OIHP-SC devices with an active area of 1 cm². In addition, the flexible TCO-free OIHP-SCs exhibit good bending stability after 5000 bending cycles at radii of 6, 4, and 2 mm and excellent light soaking stability under 1 Sun light intensity over 1000 h as opposed to the poor stability when using poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as the HTM.

Herein, it is demonstrated that a two-step postfiring bias treatment is able to evidently enhance the efficiency of commercial gallium-doped passivated emitter and rear cell solar cells by up to 0.1% absolute. Furthermore, based on the proposed new model in light of hydrogen behavior under electric field, the mechanisms underlying the two-step bias treatments on improving cell efficiency are discussed.

Passivated emitter and rear cell (PERC) solar cells have dominated the photovoltaic market in recent years. Continuously improving the efficiency of PERC solar cells is of great importance to enable the goal of low electricity cost, which is cheaper than the cost of thermal power generation. Herein, it is demonstrated that a two-step postfiring bias treatment is able to evidently enhance the efficiency of commercial gallium-doped PERC solar cells by up to 0.1% absolute. In detail, the first-step bias treatment is done by forward biasing the PERC solar cells at 12 A and 200 °C for 60 min, resulting in an average efficiency enhancement at around 0.05% absolute. The second-step bias treatment is done by reverse biasing the PERC solar cells at −0.1 or −0.2 V and at the elevated temperatures for certain times, leading to another average efficiency enhancement at around 0.05% absolute. To explore the mechanism underlying the two-step bias treatments on improving cell efficiency, a new model in light of hydrogen behavior under electric field is proposed to explain this phenomenon.

Doped hole-transporting materials from spiro cores involving 9H-quinolinophenoxazine (spiro-POZ) and 9H-quinolinophenothiazine (spiro-PTZ) show outstanding stability, retaining over 84% of their initial efficiency after more than 300 days of exposure to ambient conditions, and 94% of the power conversion efficiency values after 1200 h under continuous 1 sun illumination.

The improvement of the long-term stability of perovskite-based solar cells (PSCs) toward commercialization is closely linked to the development of cutting-edge charge-transporting materials. The progress on the design and the synthesis of new hole-transporting materials (HTMs) is synergistically attaining both top efficiencies and promising stability. Herein, the synthesis and characterization of two doped-HTMs based on electron-rich spiranic cores, namely, 9H-quinolinophenoxazine (spiro-POZ) and 9H-quinolinophenothiazine (spiro-PTZ), are presented. The novel HTMs exhibit excellent solubility, optimal highest occupied molecular orbital energy, and excellent thermal stability with glass transition temperatures higher than those for spiro-OMeTAD. [(FAPbI₃)_0.87(MAPbBr₃)_0.13]_0.92[CsPbI₃]_0.08-based solar cells using the new spiro-type HTMs deliver power conversion efficiencies (PCEs) around 17% for mesoporous cells, and higher than 18% in planar configurations, matching the PCE of spiro-OMeTAD. Remarkably, doped spiro-POZ and spiro-PTZ exhibit excellent long-term stability in planar devices, retaining over 84% of their initial efficiency after more than 300 days of exposure to ambient conditions. Furthermore, after 1200 h under continuous 1 sun illumination, the PCE of the PSCs based on spiro-POZ and spiro-PTZ decreases by only 6%.

An interdigitated bulk heterojunction structure of the active layer is developed by preforming the porous donor polymer film and then processing the acceptor on top, which yields an impressive high power conversion efficiency of 18.74% for polymer solar cells.

Abstract

The most popular approach to fabricating organic solar cells (OSCs) is solution processing a mixture of donor (D) and acceptor (A) materials into an active layer with a bulk heterojunction (BHJ) nanostructure. Herein, it is demonstrated that the interdigitated heterojunction (IHJ) is a more suitable nanostructure of the active layer for high-performance OSCs whereas it is a long standing challenge to realize well-defined IHJ structures. In this study, a facile and versatile sequential solution processing method is developed to produce an IHJ nanostructure with power conversion efficiency reaching 18.74% (18.10% for BHJ the counterpart) by fabricating a donor film with nanopores created by a wax additive, sequentially casting the acceptor on top of infiltrating the nanopores. Compared to the BHJ, the IHJ structure with an interpillar distance within the exciton diffusion length can afford a large bulk D/A interface for efficient exciton dissociation with a minimized charge recombination while free electrons and holes can transport to the respective electrodes through more straightforward pathways, thus enhance performance. Furthermore, the D or A phase in the IHJ device contacts with only one electrode, which can prevent shunting between the anode and cathode and facilitate the industrial mass production of OSCs.

Stability and toxicity of PSCs are bottleneck challenges for their commercial development. Herein, biomimetic Di-g molecules are introduced to the encapsulated FPSCs as the interface layer, which improves the efficiency of 1.01 cm² FPSCs up to 20.29%. Importantly, they demonstrate excellent mechanical stability and lead leakage suppression, the efficiency maintains 85% of initial value without ion leakage under 10 000 bending cycles.

Abstract

Although outstanding power conversion efficiency (PCE) has been achieved in flexible perovskite solar cells, unsatisfactory operational stability and toxicity caused by the moisture transmittance of polymer packaging are still the bottleneck challenges that limit their applications. Herein, inspired by the non-selective permeability of inactivated cell membrane, the diphosphatidyl-glycerol (Di-g) is tactfully introduced as a self-shield interface upon the perovskite layer. 96% of lead leakage is suppressed because the amphipathic Di-g can simultaneously bind tightly to the divalent lead ion and afford an interfacial water-resistance. More importantly, the gradient distribution of lattice residual stress perpendicular to the substrate are optimized. The resultant flexible devices achieve a PCE of 20.29% and 15.01% at effective areas of 1.01 and 21.82 cm² respectively, yielding excellent environmental and mechanical stability. This strategy exhibits the feasibility of developing interfacial encapsulation to stabilize scalable PSCs with negligible lead leakage.

Two nonhalogenated polymers, PB1 and PB2, with different side-chain orientations and deep highest occupied molecular orbital (HOMO) levels are reported. In organic photovoltaic (OPV) cells, PB1 only produces a power conversion efficiency (PCE) of 5.3%, while PB2 gives an outstanding PCE of 17.7%. More importantly, PB2 has good compatibility with various electron acceptors. PB2 achieves excellent PCEs of 18.4% and 27.1% for ternary OPV cells and indoor light photovoltaic devices, respectively.

Abstract

Nonhalogenated polymers have great potential in the commercialization of organic photovoltaic (OPV) cells due to their advantage in low-cost preparation. However, non-halogenated polymers usually have high highest occupied molecular orbital (HOMO) energy levels and inferior self-aggregation properties in solution, thus resulting in low power conversion efficiencies (PCEs). Herein, two nonhalogenated polymers, PB1 and PB2, are prepared. When the polymers are used to fabricate OPV cells with BTP-eC9, the PB1-based device only gives a PCE of 5.3%, while the PB2-based device shows an outstanding PCE of 17.7%. After the introduction of PBDB-TF as the third component, the PB2:PBDB-TF:BTP-eC9-based device with an optimal weight ratio of 0.5:0.5:1 achieves a PCE up to 18.4%. More importantly, PB2 exhibits good compatibility with various nonfullerene acceptors to achieve better PCEs than those of classical polymer (PBDB-T and PBDB-TF)-based devices. When PB2 is combined with a wide-bandgap electron acceptor (F-BTA3), this device shows excellent PCE of 27.1% and 24.6% for 1 and 10 cm² devices, respectively, under light intensity of 1000 lux light-emitting diode illumination. These results provide new insight in the rational design of novel nonhalogenated polymer donors for further development of low-cost materials and broadening the application of OPV cells.

A general mechanism for the doping-induced insulator–conductor transition in organic semiconductors is proposed. Multiscale simulations unveil the high polarizability of dopant–semiconductor complexes and predict large nonlinear enhancements of the dielectric constant as the system approaches a dielectric instability (catastrophe) upon increasing doping. Such an enhanced screening frees charges from Coulomb barriers at concentrations of 5–10%, in accordance with experiments.

Abstract

The control over material properties attainable through molecular doping is essential to many technological applications of organic semiconductors, such as organic light-emitting diodes or thermoelectrics. These excitonic semiconductors typically reach the degenerate limit only at impurity concentrations of 5–10%, a phenomenon that has been put in relation with the strong Coulomb binding between charge carriers and ionized dopants, and whose comprehension remained elusive so far. This study proposes a general mechanism for the release of carriers at finite doping in terms of collective screening phenomena. A multiscale model for the dielectric properties of doped organic semiconductor is set up by combining first principles and microelectrostatic calculations. The results predict a large nonlinear enhancement of the dielectric constant (tenfold at 8% load) as the system approaches a dielectric instability (catastrophe) upon increasing doping. This can be attributed to the presence of highly polarizable host–dopant complexes, plus a nontrivial leading contribution from dipolar interactions in the disordered and heterogeneous system. The enhanced screening in the material drastically reduces the (free) energy barriers for electron–hole separation, rationalizing the possibility for thermal charge release. The proposed mechanism is consistent with conductivity data and sets the basis for achieving higher conductivities at lower doping loads.

Publication date: 17 November 2021

Source: Joule, Volume 5, Issue 11

Author(s): Wenxiao Zhang, Xiaodong Li, Sheng Fu, Xiaoyan Zhao, Xiuxiu Feng, Junfeng Fang

This is the first example where the fused aromatic ring unit is utilized as a conjugated side chain to extend the conjugation system of small-molecular donors. This strategy effectively achieves improved short-circuit current density and fill factor in organic solar cells (OSCs). Together with Y6 as acceptor, the all-small-molecule OSC achieves an improved power conversion efficiency of 13.6%.

Side-chain engineering influences the organic solar cell (OSC) devices active layer morphology fundamentally and it is an efficient strategy to improve device performances. A novel small molecular donor with conjugated fused-aromatic-ring side chain on a benzo[1,2-b:4,5-b′]dithiophene core is developed. To the best of our knowledge, this is the first example where fused-aromatic-ring units are being utilized as conjugated side chains to extend the conjugation system of small molecular donor materials. The material property, OSC device performance, active layer morphology, and photovoltaic mechanism are investigated. This molecular design strategy has proven to be effective in fine-tuning and enhancing the molecular stacking/orientation and phase separation, which led to the enhanced charge separation and transportation, suppressed charge recombination, and as a result, devices with an improved short-circuit current density of 24.9 mA cm⁻², fill factor of 69.9%, and power conversion efficiency of 13.6% are achieved. The results reveal that a fused-aromatic-ring utilized as conjugated side chain strategy can potentially be an effective way for molecular rational design, aiming to improve the OSC performances.

Herein, by partial substitution of the A-site cation using diethylammonium iodide (DEAI), deeper energy levels are obtained. At the same time, the trap density is reduced, and the grain size is significantly improved. The fabricated solar cell shows much enhanced efficiency from 7.31% to 10.28% with the stability of 50 days maintaining 78%.

Environment-friendly tin perovskite solar cells (T-PKSCs) are the most suitable alternative candidate for lead-free PKSCs. However, the photovoltaic performance of such T-PKSCs is far below those of lead-based perovskite solar cells due to an energetic mismatch between the perovskite layer and charge transport layers. Herein, it is shown that, by partial substitution of the A-site cation using diethylammonium iodide (DEAI) substitution, deeper energy levels are obtained. At the same time, the trap density is reduced and the grain size is significantly improved. The fabricated solar cell shows much enhanced efficiency from 7.31% to 10.28%, short-circuit current density from 18.68 to 21.69 mA cm⁻², open-circuit voltage from 0.59 to 0.67 V, and fill factor from 0.67 to 0.71 after DEAI substitution. Such an efficiency improvement can be explained by matching energy levels at the interfaces between perovskite layer and the charge transport layers. In addition, after 50 days of storage, the modified T-PKSCs demonstrate high stability maintaining 78% of its initial efficiency, whereas the reference device degrades to 68% during 28 days storage.

A low energetic disorder with an urbach energy (E _U) of 23.7 meV and a low energy loss (E _loss) of 0.41 eV are achieved for the PBDS-TCl:Y6-based organic solar cells (OSCs). It is demonstrated that fine-tuning the polymer donor by functional atom modification on the side chain is a promising way to reduce E _U and E _loss, as well as obtain small driving force and high open circuit voltage for highly efficient OSCs.

Abstract

The energy loss (E _loss), especially the nonradiative recombination loss and energetic disorder, needs to be minimized to improve the device performance with a small voltage (V _OC) loss. Urbach energy (E _U) of organic photovoltaic materials is related to energetic disorder, which can predict the E _loss of the corresponding device. Herein, a polymer donor (PBDS-TCl) with Si and Cl functional atoms for organic solar cells (OSCs) is synthesized. It can be found that the V _OC and E _loss can be well manipulated by regulation of the energy level of the polymer donor and E _U, which is dominated by the morphology. A low energetic disorder with an E _U of 23.7 meV, a low driving force of 0.08 eV, and a low E _loss of 0.41 eV are achieved for the PBDS-TCl:Y6-based OSCs. Consequently, an impressive open circuit voltage (V _OC) of 0.92 V is obtained. To the best of knowledge, the V _OC value and E _loss are both the record values for the Y6-based device. These results demonstrate that fine-tuning the polymer donor by functional atom modification on the side chain is a promising way to reduce E _U and energy loss, as well as obtain small driving force and high V _OC for highly efficient OSCs.

High-performance organic solar cells (OSCs) are feasibly obtained from the hot spin coating of different kinds of non-halogenated solvents. It is revealed that the blend phase evolution during solution-to-solid transition has a correlation to the substrate temperature. As result, high-performance OSCs are obtained with power conversion efficiencies of 18.25% in o-xylene, 18.20% in p-xylene, and 18.12% in toluene, respectively.

Abstract

High-performance organic solar cells (OSCs) at the current stage are majorly accomplished from the processing of halogenated solvents, such as chloroform, which will be constrained for upscale fabrication due to the adverse health and environmental impacts. Therefore, exploring the high-performance OSCs from non-halogenated solvent processing becomes highly necessary, yet largely lagged behind. Herein, it is demonstrated high-performance OSCs can be obtained from the hot spin processing of different non-halogenated solvents, and achieve the highest reported efficiency of OSCs from non-halogenated solvent processing so far. It is revealed that the phase evolution of ternary blends during solution-to-solid transition has a correlation to the substrate temperature. With the elevated substrate temperature of hot spin coating, the optimal blend films can be secured in different kinds of non-halogenated solvents. As result, high-performance OSCs are obtained with excellent power conversion efficiencies of 18.25% in o-xylene, 18.20% in p-xylene, and 18.12% in toluene, respectively. To the author's best knowledge, these results represent the best-performed OSCs made from non-halogenated solvents so far.