To develop novel hole-transport materials (HTMs) with less synthetic steps is still a great challenge. Here, a small molecule hexakis[4-(N,N-di-p-methoxyphenylamino)phenyl]benzene (F-1) was successfully synthesized by a relatively simple scenario. F-1 exhibits a deep highest occupied molecular orbital energy level of −5.31 eV. Notably, F-1 also features 2 times higher hole mobility of 4.98 × 10–4 cm2 V–1 s–1 than that of the mostly used 2,2′,7,7′-tetrakis(N,N-bis(4-methoxyphenyl)amino)-9,9′-spirobifluorene (spiro-OMeTAD). Consequently, F-1-based perovskite solar cells (PSCs) show markedly improved performance compared with spiro-OMeTAD-based ones. These results indicate such a material can be a promising HTM candidate to boost the overall performance of the PSC.Keywords: deep energy level; high efficiency; high mobility; hole-transport material synthesis; perovskite solar cell;

Two kinds of new conjugated polymers (P1 and P2) with benzothiadiazole as the acceptor unit and thiophene as the donor unit were designed, synthesized and used as donor materials for polymer solar cells (PSCs). These polymers show a broad absorption in the visible region, a medium band gap of about 1.75 eV, and a low-lying HOMO energy level of about −5.65 eV. The open-circuit voltage (Voc) of both P1 and P2 was greatly improved to 0.85 V mainly due to the introduction of a carboxylate group at the 3-position of the thiophene spacer. Fluoro substitution on the polymer backbone of P2 can greatly enhance the interchain interaction, leading to a huge increase of short-circuit current density (Jsc). P2-based devices with the active layer spin-coated from 1,2-diclorobenzene (DCB) solutions that contain 1% 1,8-diiodooctane (DIO) and washed with methanol showed a synergistic positive effect, resulting in a significant enhancement of the power conversion efficiency (PCE) up to 8.67%. The PCE could be further improved by constructing inverted devices and the best efficiency of 9.26% was finally obtained. In addition, the mechanism for achieving such a high PCE for P2 based devices was also proposed based on the morphological analysis of the blend films by atomic force microscopy (AFM), transmission electron microscopy (TEM), grazing incident angle X-ray scattering (GIWAXS) and resonant soft X-ray scattering (RSoXS). The improvement can be ascribed to the enhanced molecular packing and proper phase separation of the blend films and the reduced charge recombination.

A new 1,8-naphthalimide based planar small molecular acceptor and two benzothiadiazole based wide band gap (WBG) polymer donors P1 and P2 were synthesized for nonfullerene organic photovoltaic cells (OPVs). Devices based on fluorinated polymer P2 achieved a highly improved PCE of 3.71% with an open circuit voltage (Voc) of 1.07 V, which is beyond the currently known levels for nonfullerene OPVs with the Voc higher than 1 V.

We investigated photovoltaic performances of polymer solar cells depending on three materials (P1/PC71BM, P2/PC71BM, P3/PC71BM) that embedded with a certain sized (35 nm) Ag nanoparticles (NPs) between indium tin oxide (ITO) and PEDOT:PSS anode buffer layer. The power conversion efficiency of the three solar cells enhanced by 13.6%, 21.1%, and 16.0%, respectively, and the increase mainly originated from Jsc. The other measurements and investigations demonstrated that both the optical and electrical properties made contributions to the development of device performances. The introduction of Ag NPs between ITO substrates and PEDOT:PSS layers is one of the most effective approaches to improve the polymer solar cell performance.

A series of new conjugated polymers (P1–P3) with 3,6-difluorocarbazole as a donor unit and benzoxadiazole as an acceptor unit were synthesized and used as donor materials for polymer solar cells (PSCs). The morphology of blend films was regulated by controlling the drying process via tuning the solubility of polymers and using solvent additives. Enhancing the solubility of polymers via increasing the volume of side chains can decrease the domain size of polymers and using 1,8-diiodooctane (DIO) as a solvent additive can give an even better vertical phase separation, leading to a significant enhancement of the power conversion efficiency (PCE) of up to 5.71% for P3 based PSCs. The improving of the interface between polymers and PC71BM phases as well as the formation of vertical phase separation after using DIO as an additive are probably responsible for the high open circuit voltage (Voc) of devices.

The use of a commercially available nucleating agent as the additive for the fabrication of polymer:PC71BM-based active layers by solution-processing can greatly enhance the power conversion efficiency (PCE) of bulk heterojunction polymer solar cells (BHJ PSCs). The enhancement of device performance is mainly due to the addition of nucleating agent, which is able to regulate the drying process of the active layer and decrease the oversized domain size of conjugated polymers. Via this effective strategy to optimize the film morphology, the designed device exhibits an enhancement as great as 30.8%.Keywords: conjugated polymers; domain size; morphology control; nucleating agent; polymer solar cells

A new 1,8-naphthalimide based planar small molecular acceptor and two benzothiadiazole based wide band gap (WBG) polymer donors P1 and P2 were synthesized for nonfullerene organic photovoltaic cells (OPVs). Devices based on fluorinated polymer P2 achieved a highly improved PCE of 3.71% with an open circuit voltage (Voc) of 1.07 V, which is beyond the currently known levels for nonfullerene OPVs with the Voc higher than 1 V.

A series of new conjugated polymers (P1–P3) with 3,6-difluorocarbazole as a donor unit and benzoxadiazole as an acceptor unit were synthesized and used as donor materials for polymer solar cells (PSCs). The morphology of blend films was regulated by controlling the drying process via tuning the solubility of polymers and using solvent additives. Enhancing the solubility of polymers via increasing the volume of side chains can decrease the domain size of polymers and using 1,8-diiodooctane (DIO) as a solvent additive can give an even better vertical phase separation, leading to a significant enhancement of the power conversion efficiency (PCE) of up to 5.71% for P3 based PSCs. The improving of the interface between polymers and PC71BM phases as well as the formation of vertical phase separation after using DIO as an additive are probably responsible for the high open circuit voltage (Voc) of devices.

Two kinds of new conjugated polymers (P1 and P2) with benzothiadiazole as the acceptor unit and thiophene as the donor unit were designed, synthesized and used as donor materials for polymer solar cells (PSCs). These polymers show a broad absorption in the visible region, a medium band gap of about 1.75 eV, and a low-lying HOMO energy level of about −5.65 eV. The open-circuit voltage (Voc) of both P1 and P2 was greatly improved to 0.85 V mainly due to the introduction of a carboxylate group at the 3-position of the thiophene spacer. Fluoro substitution on the polymer backbone of P2 can greatly enhance the interchain interaction, leading to a huge increase of short-circuit current density (Jsc). P2-based devices with the active layer spin-coated from 1,2-diclorobenzene (DCB) solutions that contain 1% 1,8-diiodooctane (DIO) and washed with methanol showed a synergistic positive effect, resulting in a significant enhancement of the power conversion efficiency (PCE) up to 8.67%. The PCE could be further improved by constructing inverted devices and the best efficiency of 9.26% was finally obtained. In addition, the mechanism for achieving such a high PCE for P2 based devices was also proposed based on the morphological analysis of the blend films by atomic force microscopy (AFM), transmission electron microscopy (TEM), grazing incident angle X-ray scattering (GIWAXS) and resonant soft X-ray scattering (RSoXS). The improvement can be ascribed to the enhanced molecular packing and proper phase separation of the blend films and the reduced charge recombination.

We investigated photovoltaic performances of polymer solar cells depending on three materials (P1/PC71BM, P2/PC71BM, P3/PC71BM) that embedded with a certain sized (35 nm) Ag nanoparticles (NPs) between indium tin oxide (ITO) and PEDOT:PSS anode buffer layer. The power conversion efficiency of the three solar cells enhanced by 13.6%, 21.1%, and 16.0%, respectively, and the increase mainly originated from Jsc. The other measurements and investigations demonstrated that both the optical and electrical properties made contributions to the development of device performances. The introduction of Ag NPs between ITO substrates and PEDOT:PSS layers is one of the most effective approaches to improve the polymer solar cell performance.