Nitroxide radical-conjugated polymer additives (nr-PAs) have been employed as newly emerged additives to mitigate the non-radiative energy loss (Elossnon_ rad), thus to boost the performance and stability of the non-fullerene acceptors-based organic solar cells (NFAs-OSCs). Herein, the small molecular nitroxide radical compounds (SMTEMPO) of racemic 4-glycidyloxy-substituted 2,2,6,6-tetramethylpiperidine-1-oxyl (GTEMPO), the stereoisomers of (R)-GTEMPO and (S)-GTEMPO, are employed as the additives for NFAs-OSCs. Upon addition of 1.0 wt% (relative to the weight of polymer donor) of the SM-TEMPO radical additives, the power conversion efficiencies (PCEs) of the devices improved as follows: PM6:Y6: from 15.73% (pristine) to 16.46% (GTEMPO), 17.20% ((R)GTEMPO), and 16.91% ((S)-GTEMPO). D18-Cl:L8-BO: from 17.53% (pristine) to 18.66% (GTEMPO), 19.42% ((R)-GTEMPO), and 19.38% ((S)-GTEMPO). On the contrary, the addition of the unglycidylated 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical additive always results in a slight decrease in the PCEs of the PM6:Y6based NFAs-OSCs. Moreover, the reasons behind the performance enhancement, as well as the specific correlation between the improved performances of NFAs-OSCs and the difference in aggregation behaviours between the SM-TEMPO and TEMPO radical additives, are investigated and discussed through a set of physical investigations of representative PM6:Y6-based blends and devices. This work not only demonstrates that SMTEMPO radical additives, which tend to aggregate in the active layer, can serve as effective additives to improve the performance and stability of the NFAs-OSCs as their nr-PAs counterparts, but also points towards simpler avenues for the development of the nitroxide radical-based additives to achieve high-performance NFAsOSCs with enhanced stability.

A series of nitroxide radical conjugated polymers (PBDT-NOx), specifically named PBDT-NO100, PBDT-NO60, PBDT-NO40, PBDT-NO20, and PBDT-NO5, are synthesized via palladium-catalyzed Stille coupling polymerization. These polymers are accordingly constructed from 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl) (BDT), 1,3-bis(5-bromothiophen-2-yl)-5,7-dioctyl-4H,8H-benzo[1,2-c:4,5-c']dithio-phene-4,8-dione (BDD), and 1,4-bis(4-oxy-2,2,6,6-tetramethylpiperidine-1-oxyl)phthalate (BTMP), with their molar feed ratios systematically varied from 50:0:50 to 50:45:5. The chemical structures, molecular weights, and optoelectronic properties are characterized. Upon the addition of the PBDT-NOx as additives, the power conversion efficiencies (PCEs) of the PM6:Y6-based non-fullerene-based organic solar cells (NFAs-OSCs) are increased from 15.62% to 16.71%-17.04%, contributed by the improvement of the electron and hole mobility, reduced charge carriers' recombination, and mitigation of the non-radiative energy loss, thus leading to PCE improvements of the NFAs-OSCs. Furthermore, the utilization of the representative PBDT-NO60 as a solid additive for the hole transporting layers (HTL) of Spiro-OMeTAD with Li-TFSI for the Cs0.05Rb0.05(FA0.83MA0.17)0.90Pb(I0.95Br0.05)3 based perovskite of solar cells (PSCs), which result in the improvement of the hole mobility of HTL, reduced carrier recombination, and enhanced carrier extraction, therefore leading to PCE improvements from 19.31% to 21.17% the PSCs, are supported an discussed.

While graphene additives demonstrably mitigate sulfation in lead-carbon battery negative plates through electric double-layer capacitance (EDLC) mechanisms or catalytic PbSO4 reduction, their practical application is hampered by the exacerbation of hydrogen evolution side reactions (HER), which accelerate water decomposition. To resolve this conflict, we developed Pb@CN@rGO composites featuring nitrogen-lead dual-active sites through in situ growth of g-C3N4 on reduced graphene oxide followed by anchoring Pb single atoms. Specifically, g-C3N4-derived N sites enhance EDLC performance and suppress HER by raising H-atom adsorption energy, enabling covalent hydrogen trapping. Concurrently, Pb sites fulfill dual functions: further inhibiting HER via Nsite modulation, and guiding Pb/PbSO4 growth within the negative active material (NAM) through optimized adsorption and metal-bonding-mediated nucleation. This synergistic action simultaneously strengthens graphene-NAM interfacial bonding and optimizes NAM morphology. Furthermore, through this synergistic design, the N-Pb dual sites enable cooperative charge storage by making the EDLC potential window of Pb@CN@rGO compatible with the Pb/PbSO4 redox potential range, where nitrogen-mediated H+ separation/ neutralization is complemented by Pb-driven Faradaic reactions. Remarkably, Lead-carbon batteries (LCBs) incorporating 0.5 wt% 10 %Pb@CN@rGO additives achieved 24,736 high-rate partial state of charge (HRPSoC) cycles at 50 % SOC. This represents a twofold improvement over batteries with g-C3N4@rGO additives (12,344 cycles) and a 6.5-fold longevity increase compared to commercial lead-acid batteries (3826 cycles). This work establishes a cooperative site design paradigm that simultaneously addresses sulfation mitigation, parasitic HER suppression, and NAM structural reinforcement, providing a new strategy for developing durable energy storage systems for renewable energy grid applications.

The larger non-radiative energy loss (Delta Vnon-radoc) of the non-fullerene-based organic solar cells (NFAs-OSCs) has been demonstrated to be the main barrier to further boosting the efficiency of NFAs-OSCs. In response, extensive studies have been implemented, focusing on the optimization of the photoactive layer morphology, molecular engineering of donors and acceptors, and the development of multi-component NFAs-OSCs etc., thereby achieving a series of devices with markedly enhanced performance. As an emerging strategy, the utilization of nitroxide radical-conjugated polymer additives is also worthy of attention due to their ability to simultaneously enhance the performance and stability of NFAs-OSCs. In this study, the racemic and isotactic nitroxide radical polymonothiocarbonates (PTC-NOs, with the specific names of Rac-PTC-NO, (R)-PTC-NO and (S)-PTC-NO) are employed as solid additives to mitigate the Delta Vnon-radoc of the NFAs-OSCs. Upon the addition of 0.5 wt% of Rac-PTC-NO, (R)-PTC-NO and (S)-PTC-NO, the PCEs of the PM6:Y6-based NFAs-OSCs are respectively improved from 15.73% to 16.59%, 17.30% and 17.40%. Besides, the reasons behind the improvement in the performance of the NFAs-OSCs from the representative photovoltaic material pair of PM6:Y6, such as the increase of the exciton dissociation probability, suppression of charge carrier recombination and mitigation of the non-radiative energy loss of the devices upon the addition of the PTC-NOs additives, are supported by and discussed through a set of comparative investigations. This work not only broadens the scope but also provides new insights for designing and developing efficient nitroxide radical-based polymeric additives to mitigate the non-radiative energy loss, thus further boosting the performance of NFAs-OSCs.

Free radical-containing polymer additives have demonstrated remarkable efficacy in the mitigation of energy losses, the suppression of triple exciton concentration, and the optimization of charge transport in organic solar cells (OSCs) devices. To further explore the reasons why free radical additives with different molecular structures enhance the performance enhancement of organic solar cells, in this study, PBN-NO free radical polymer was added with a dopant in the active layer of PBDBT:ITIC, and the performance of the PBDB-T:ITIC-based device was significantly improved by adding 0.3 % of PBN-NO, and the power conversion efficiency (PCE) was boosted from 9.49 % to 11.13 %. Magneto-optical current measurements and Coulomb capture radius calculations revealed that optimized morphologies assisted by PBN-NO contribute to the suppressed charge recombination, regulated polaron pairs, reduced exciton recombination and enhanced charge transportation, leading to simultaneous enhancements in short-circuit current density (JSC) and fill factor (FF). Compared with the control devices, the JSC was increased to 16.19 mA cm- 2 and the FF was significantly improved to 74.59 %. Likewise, a slight increase in the open-circuit voltage (VOC) of the devices with the addition of PBN-NO was confirmed based on the dark-state photovoltaic performance and energy loss. Furthermore, the effectiveness of PBN-NO as an additive has been demonstrated in various systems, where the PCE of devices based on PM6:Y6 was improved from 15.82 % to 16.89 %. This work provides a new solution to improve the performance of OSCs by controlling Coulomb capture radius, suppressing exciton recombination and enhancing charge separation and transport.

Molecular halogenation enables precise adjustment of polymer electronic distribution without altering absorption spectra, while simultaneously strengthening intermolecular interactions and shortening pi-pi stacking distances to facilitate charge transport. In this study, dithieno[3,2-b:2 ',3 '-d]benzo[1,2-b:4,5-b']dithiophene copolymers, named PBT-SBDD, PBTCl-SBDD, and PBTF-SBDD, respectively, were designed and synthesised through side-group halide engineering, and employed as donor materials in the active layer of semi-transparent organic solar cells (ST-OSCs). With the introduction of fluorine and chlorine atoms, the device exhibited enhanced absorption in the wavelength range of 400 to 500 nm, a key factor in balancing transparency and energy conversion efficiency. The average visible transmittance (AVT) values of the PBTCl-SBDD- and PBTFSBDD-based devices reach 21.3 % and 20.2 %, respectively, which is a significant enhancement compared to 12.5% in the non-halogenated PBT-SBDD devices. The power conversion efficiencies (PCEs) of the PBTCl-SBDD: Y6 and PBTF-SBDD: Y6 devices were 9.54 % and 9.48 % respectively, representing enhancements of 2.21 % and 2.15 % compared to the PBT-SBDD: Y6 device with a PCE of 7.33 %. The corresponding light utilisation efficiencies (LUEs) are simultaneously increased to 2.0 % and 1.9 % compared to 0.9 % for the PBT-SBDD: Y6 device, respectively. Further analysis revealed that halogenation optimised charge transport by intensifying intermolecular interactions and reducing pi-pi stacking distances. This simultaneously suppressed non-radiative recombination losses and improved exciton dissociation efficiency. Furthermore, halogenation promoted smoother blend film morphology, increased crystallinity, and improved donor-acceptor compatibility, collectively enhancing device performance. This work demonstrates that halogenation engineering can effectively optimise polymer properties without compromising transparency, offering a viable pathway towards high-performance devices.

A series of novel dual-state luminescent (DSE) polymers were synthesized by Suzuki coupling reaction, and their optical properties and potential applications as color conversion materials in agriculture were studied. A series of characterizations prove that the synthesized DSE polymer has excellent color conversion ability and good luminescence properties. The prepared light conversion agent was doped into polymethyl methacrylate (PMMA), and the optical conversion film was prepared by adjusting the doping amount, and its optical properties were analyzed. The results show that the light conversion film not only has good performance of converting ultraviolet light into blue light (400-480 nm), but also has good light transmittance for blue light and red-orange light (600-700 nm), which is beneficial to plant growth. The efficiency of plants using light energy is significantly improved, which is expected to greatly improve the quality and efficiency of agriculture.

Three narrow bandgap alternating conjugated polymers of PBDT‐TT, PBDT‐2F‐TT, and PBDT‐4F‐TT, which accordingly derived from 2‐(2‐ethylhexyl)thiophene, 2‐(2‐ethylhexyl)‐3‐fluorothiophene and 2‐(2‐ethylhexyl)‐3,4‐difluorothiophene flanked benzo[1,2‐ b :4,5‐ b ’]dithiophene (BDT) and 2,5‐bis(4‐(ethylhexyl)thiophen‐2‐yl)thienothiadiazole (TT), are synthesized by Palladium‐catalyzed Stille coupling reaction. The absorption, thermal stability, and electrochemical properties of the copolymers are characterized. It is found that, with the increase of the fluorine atoms in the BDT blocks of the copolymers, the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) energy levels, and decomposition temperatures of the copolymers, are successively varied from −5.16 to −5.30 eV, −3.98 to −4.09 eV, and 364 to 384 °C. The specific detectivity ( D * ) at 790 nm and linear dynamic range (LDR) of the polymer photovoltaic photodetectors (PPDs) from the PBDT‐TT:Y6, PBDT‐2F‐TT:Y6 and PBDT‐4F‐TT:Y6 blend films, are ordinally increased from 7.54 × 10 11 Jones and 53.5 dB to 1.79 × 10 12 Jones and 87.0 dB, and then up to 4.23 × 10 12 Jones and 88.7 dB under −0.1 V bias voltage. Moreover, the possible reasons for the successive improvements in the performance of the PPDs from the BDT‐alt‐TT copolymers with the increase of the fluorine atoms in the BDT units are investigated and discussed.

Continuous interpenetrating network morphology on the performance of organic solar cells (OSCs) have the effect of ease, how to control the bulk heterojunction (BHJ) the formation of the fiber morphology is of vital importance. In this study, a series of polymers were synthesized by rationally varying the atoms connecting the conjugated backbone and side chains, PBDT-T-SBDD, PBDT-TS-SBDD and PBDT-TDS-SBDD were used to systematically study the effects of sulfur atom on the electron conformation of the molecule, the morphology of the blend film and the properties of the device. We found that the introduction of sulfur atoms can enhance the intermolecular interaction, thus reducing the energy disorder of the blend film. However, excessive introduction of sulfur atoms leads to excessive steric hindrance of side chain of the molecules, resulting in excessive local aggregation. Compared with PBDT-T-SBDD: Y6 and PBDT-TDS-SBDD: Y6-based OSCs, PBDT-TS-SBDD: Y6-based OSCs has both higher photovoltaic performance, reaching a PCE of 11.33 %, due to the well-defined fiber structure which significantly improves the charge transport channel and phase separation of the blend film.

Cathode interface layers (CILs), which are often built between the active layer and the metal cathode to facilitate electron collection and extraction, are highly necessary to develop stable and efficient organic solar cells (OSCs). However, most CILs are usually very sensitive to film thickness and work only in ultrathin films. In this study, 4,8-bis((N,N-dimethylamino)propyloxy)benzo[1,2-b,4,5-b']dithiophene (BDT-N) is utilized as an electron-attracting additive for sequential-deposited (SD) OSCs made from the nonfullerene acceptor (NFA) Y6 paired with the polymer donor PM6. Upon addition of 0.3 wt % of BDT-N to the Y6 layers, the power conversion efficiencies (PCEs) of the CIL-free SD-NFA OSCs with the device configuration ITO/PEDOT:PSS/PM6/Y6 without/with BDT-N/Ag improved from 6.93 to 15.13%, alongside a remarkable improvement in the stability of the devices. Meanwhile, the possible reasons behind the lowering of the work function of Ag metal cathodes, facilitating the electron attraction of the devices, etc. through the addition of the BDT-N additive are supported and discussed by a set of comparative experiments, such as ultraviolet photoelectron spectroscopy (UPS), capacitance-voltage (C-V) measurements, charge-carrier recombination measurements, etc. This work outlines a facile and promising approach to avoid the utilization of ultrathin CILs in the SD-NFA OSCs and to simplify the device fabrication.

Minimizing non-radiative energy losses (E-non-rad(Loss)) has been crucial to further boosting the efficiency of non-fullerene organic solar cells (NFAs-OSCs) to a new performance regime. Recently, we have developed an alternating radical conjugated polymer named GDTA from 3,4-dioctylthiophene flanked benzo[1,2-b;4,5-b']dithiophene (BDT) and 1,4-bis(4-oxy-2,2,6,6-tetramethylpiperidine-1-oxyl)phthalate (BTMP), and demonstrated that GDTA can be used as additives to improve the performance of OSCs from a broad of photovoltaic materials system. Herein, the GDTA is accordingly optimized by varying the molar feed ratios of monomers containing BTMP and BDT moieties from 9:11, 2:3, 3:7 and 1:4, to generate the random radical conjugated polymers (R-RCPs) of R-GDTA90, R-GDTA80, R-GDTA60, R-GDTA40. For the NFAs-OSCs from PM6:Y6 blends, the addition of all the R-RCPs additives results in the general improvement of the efficiency of 9.3-11.5 % (16.12 % to 17.62 % similar to 17.98 %). On contrary, the efficiencies of the devices from D18-Cl: L8-BO blends are firstly increased to 19.32 %, 19.02 % and finally dropped to 17.29 %, as the R-GDTA90, R-GDTA80, R-GDTA60 and R-GDTA40 are separately used as additives. The particularly interesting NFAs-OSCs, which present higher efficiency of 17.98 % and 19.32 % than those of 17.62 % and 18.78 % for devices with the counterpart GDTA additives, were achieved from PM6: Y6 and D18-Cl: L8-BO with the 2.0 wt% of R-GDTA80 and R-GDTA90 additives, respectively. Besides that, the more efficiently suppressed charge recombination and energy loss of the devices with the best-fitting R-RCPs in contrast to NFAs-OSCs with GDTA additives, were observed and supported by a range of physical measurements.

Understanding the impact of molecular structure on the molecular packing arrangement and aggregation behaviors of organic semiconductor materials is crucial for investigating their properties in multiple organic photoelectrical applications. In this study, a high-performance polymer donor based on dithieno[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene (DTBDT) and 5,6-difluorobenzo[c][1,2,5]thiadiazole (FBT) unit, named PDTBDT-Cl-TFBT, was designed and synthesized by introducing an asymmetric 3-octylthiophene π-bridge between the donor and acceptor segment. The density functional theory (DFT) calculation reveals that the asymmetric π-bridge increases the average dipole moment of the repeating units as well as the configurational disorder in polymer PDTBDT-Cl-TFBT, resulting in the overall diminished self-aggregation and crystallinity, which leads to higher miscibility with the nonfullerene acceptor Y6 than that of the symmetric π-bridge-modified polymer PDTBDT-Cl-DTFBT. This feature leads to a suitable phase separation in the PDTBDT-Cl-TFBT:Y6 blend and contributes to better photovoltaic performance. As a result, organic solar cells (OSCs) based on PDTBDT-Cl-TFBT:Y6 achieve a notably higher power conversion efficiency (PCE) of 14.13%, surpassing the performance of that based on PDTBDT-Cl-DTFBT:Y6 (9.63%). Detailed analyses indicate that the performance enhancement is primarily attributed to the reduced trap density, mitigated energetic disorder, improved charge transport, and suppressed charge recombination. This research uncovers an effective strategy for optimizing the film morphology and photovoltaic performance of DTBDT-based polymer donors.

The large non-radiative recombination losses (Delta Vnon-radoc) of non-fullerene acceptor-based organic solar cells (NFA-OSCs) were recognized as the main limitation to further boosting their efficiency to a new regime. In this report, three nitroxide radical modified PM6 analogous polymers labeled as PM6-BTMP1, PM6-BTMP2 and PM6-BTMP5 were built from 2,6-bis(trimethylstannyl)-4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b ']dithiophene (BDT-FSn) and 1,3-bis(5-bromothiophen-2-yl)-5,7-bis(2-ethyl-hexyl)benzo[1,2-c:4,5-c ']dithiophene-4,8-dione (BDDBr) through embedding the third nitroxide radical component 2,5-dibromo-1,4-bis(4-oxy-2,2,6,6-tetramethylpiperidine-1-oxyl)phthalate (BTMP) with molar feed ratios of 50 : 49 : 1, 50 : 48 : 2 and 50 : 45 : 5. With the incorporation of a small amount of BTMP blocks containing nitroxide radicals in terpolymers, the absorption and electrochemical characteristics were almost not changed as compared to the notable PM6, but the power conversion efficiencies (PCEs) of the NFA-OSCs from the blends of BTMP-modified PM6 polymers paired with Y6 were decreased to 12.65-13.38% in contrast to that of 15.87% for the devices from PM6:Y6, alongside the decrease of Delta Vnon-radoc and a remarkable increase in open circuit voltages (VOCs), as well as a decline in short current densities (JSCs) and fill factors (FFs). Interestingly, upon the utilization of the BTMP-modified PM6 polymer as a solid additive, the PCEs of the devices from PM6:Y6 were improved by 1.64-12.67% relative to that of 15.78% for the NFA-OSCs from the pristine PM6:Y6 blends (PCEs, 15.87% vs. 16.13-17.88%). Particularly interesting NFA-OSCs, which presented a PCE of 17.88%, were realized in the devices with 2.0 wt% PM6-BTMP2 additives. Besides these, the reasons behind the observed decrease in the performance and mitigated Delta Vnon-radoc of the devices from the BTMP-modified PM6 as donors, as well as the improvement of the PCEs in the NFA-OSCs with BTMP-modified PM6 as solid additives, were investigated by a set of physical measurements. The results not only point to a potential avenue to develop novel polymer donors to mitigate the Delta Vnon-radoc of the NFA-OSCs, but also provide a supplement to further optimize the nitroxide radical polymer additives to boost the efficiency of organic solar cells.

In recent years, polymerized small molecule acceptors (PSMAs) have emerged as a promising strategy that combines the strong absorption of small molecules with the film-forming ability and stability of polymers, thereby greatly boosting the performance of all-polymer solar cells (all-PSCs). We designed a non-fused acceptor, DTBT-IC, and its polymeric counterpart, PDTBT-Br-T, by selecting DTBT as the core, bithiophene as the pi-bridge, and IC as the terminal group. PDTBT-Br-T was synthesized via Stille coupling and used with PM6 as the donor to fabricate organic solar cells. The PDTBT-Br-T-based device delivered superior performance, with a VOC of 1.050 V, JSC of 9.32 mA cm-2, FF of 45.33%, and a PCE of 4.44%, outperforming the DTBT-IC-based counterpart. Morphological and structural analyses revealed that PDTBT-Br-T exhibits more ordered backbone stacking and defined phase separation, enhancing exciton dissociation and charge transport, and suppressing energy loss. The study highlights that polymerization of DTBT-IC enhances intermolecular packing and microstructure, offering critical design insights for efficient all-PSCs.

Europium oleate (Eu(OA)3) is designed as a multifunctional passivation layer coated onto methylammonium lead iodide (MAPbI3) films to delay the degradation of perovskite solar cells (PSCs) caused by moisture and heat. The carbonyl group and Eu3+ ions of Eu(OA)3 subsequently coordinate with uncoordinated Pb2+ and I- ions to form a moisture-proof and heat-dissipating layer anchored onto both top and side surfaces of the perovskite film. The hydrophobicity of the MAPbI3 film treated by Eu(OA)3 remarkably increases, as demonstrated by the enhancement of the average contact angle from 54.9° to 90.5°. Besides, the thermal conductivity of PSCs incorporated with Eu(OA)3 is 1.3 times that of the control device, resulting in a 1.34 °C reduction on surface temperature at 85 °C. The optimized PSCs demonstrate a T80 lifetime of 1056 h (only 180 h for pristine PSCs) at conditions of room temperature and relative humidity (RH) of 40%. Moreover, the T80 lifetime for optimized PSCs is four times that of the control device at 85 °C and RH of 85%. Finally, the power conversion efficiency (PCE) of PSCs treated with Eu(OA)3 increases from 17.36 to 18.99%, attributed to the effective defect passivation and suppression of nonradiative recombination.

Two wide band gap conjugated polymers labeled PDBT-DTPz-Cl and PDBT-DTPz-F, deriving from 4,8-di(5-(2-butyloctyl)-4-chlorothiophen-2-yl)dithieno[3,2-d,3 ',2 '-d ']benzo[1,2-b;4,5-b ']dithiophene and 9,10-dichloro-2,5-bis((4-hexyldecyl)thiophen-2-yl)dithieno[3,2-a:2 ',3 '-c]phenazine or 9,10-difluoro-2,5-bis((4-hexyldecyl)thiophen-2-yl)dithieno[3,2-a:2 ',3 '-c]phenazine, are synthesized by the Palladium-catalyzed Stille coupling reaction, and characterized by UV-vis absorption, gel chromatography (GPC) and cyclic voltammetry (CV) etc. The polymers exhibit extensive light-harvesting ability in the region of 300-700 nm alongside the lowest unoccupied (LUMO) and highest occupied molecular orbital (HOMO) energy levels of -3.92 and -5.59 eV for PDBT-DTPz-Cl and -3.98 and -5.65 eV for PDBT-DTPz-F. Besides that, the non-fullerene-based organic solar cells (NFAs-OSCs) from the blends of PDBT-DTPz-Cl:Y6 and PDBT-DTPz-F:Y6, which respectively present efficiencies of 9.41% and 13.16%, were achieved. The enhanced performance of devices fabricated from PDBT-DTPz-F:Y6, as compared to those from PDBT-DTPz-Cl:Y6, is attributed to several key factors. These include the higher charge mobility of the blend films, the increased probability of exciton dissociation, and the reduced bimolecular, triplet-assisted recombination, and non-radiative energy losses. These improvements are thoroughly discussed and corroborated by a comprehensive suite of physical measurements.

Fluorine side chain engineering has been widely used to optimize the organic photovoltaic materials via the regulation of the energy levels, crystallinity, and mitigation of the non-radiative energy loss (Delta E-nr) of the devices from them as well. Herein, the notable wide bandgap conjugated polymeric donor materials of D18 were optimized by the introduction of the third component of 4,8-di(3,4-difluoro-5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b']dithiophene (BDT-4F) to generate the polymers with the name of D18-4F-5, D18-4F-10, D18-4F-20, D18-4F-30, and D18-4F-100 as well. As compared with the D18, the absorption spectra of analogous polymers of the D18 were almost not changed in the solid state, but the highest occupied molecular orbital (HOMO) energy levels were successively deepened, alongside the gradually increasing pi-pi stacking distance and decreasing the d-interlayer spacing distance in the solid state. In parallel, the open circuit voltage (V-OC) of the non-fullerene-based organic solar cells (NFAs-OSCs) from the blends of the polymers paired with Y6 were increased from 0.860 V to similar to 0.876 V-0.874 V, and then up to 0.892 V, alongside the decrease of the short current density (J(SC)) from 27.61 mA/cm(2) to 20.59 mA/cm(2), fill factors (FF) from 76.29 % to 53.11 %. The particular interest NFAs-OSCs with the higher power conversion efficiency (PCE) of 18.11 % relative to that of 16.89 % for the counterpart devices from the blends of D18:Y6, is achieved from the D18-4F-10:Y6 blends. Beyond that, the more balanced charge transporting, efficiently suppressed charge bimolecular recombination, and lower Delta E-nr etc. of the devices of the D18-4F-10:Y6 as compared with D18:Y6, were observed and supported by a range of physical measurements.

Modification of conjugated polymer skeletons using side chain engineering is important for the development of efficient conjugated donor polymers. In this work, alkylthio-substituted BDD units (SBDD) were introduced into the high-efficiency donor PM6 to construct a series of conjugated polymers (PBDB-TF-S5, PBDB-TF-S10 and PBDB-TF-S20, with the molar ratios of SBDD of 5%, 10%, and 20%, respectively), and the effect of the third component SBDD on the photovoltaic performance of organic solar cells (OSCs) was systematically investigated. First, we demonstrated that the highest occupied molecular orbital energy level (EHOMO) of polymers gradually decreases when the content of SBDD increases, which facilitates the obtainment of progressively higher open-circuit voltages (VOC) for the corresponding devices. Second, the detailed experimental results proved that OSCs based on PBDB-TF-S5:Y6 revealed a lower energy loss (Eloss), suitable degree of crystallinity, good miscibility with Y6, more balanced carrier mobilities and weaker charge recombination. Eventually, the power conversion efficiency (PCE) of the device based on PM6:Y6 (15.47%) was increased to 16.46% with a JSC of 25.68 mA cm-2, VOC of 0.861 V and fill factor (FF) of 74.45% with the help of an alkylthio side chain. This work provides a sufficient reference for optimizing the efficient donor polymer PM6 and confirms that PBDB-TF-S5 is a promising and efficient donor polymer for OSCs.

For the purpose of examining the influence of the number of fluorine atoms on the open-circuit voltage (VOC) in photoelectric devices, the polymers PBDT-0F-G, PBDT-2F-G, PBDT-4F-G were synthesized. These side chains of the polymer were substituted by fluorine atoms in different quantities and the photovoltaic properties were characterized. The introduction of F atoms on the side chain has a deeper molecular orbital energy level than the polymer without F atoms. Thus, the introduction 4 F atoms enhanced the VOC, with an increased to 0.97 V, compared with 0.95 V in the control device. In addition, fluoridation also improves the dielectric constant, especially when the side chain was enhanced by 4 fluorine atoms, the epsilon r of PBDT-4F-G at 10 kHz was measured to be 4.5, which is higher than that of PBDT-2F-G (3.1) and PBDT-0F-G (2.9). Thus, the carrier mobility in the bulk heterojunction (BHJ) blends was improved. The results show that the improvement of devices performance is caused by introduction of F atoms.