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Material chemical structure – intrinsic photostability relationships are revealed for a family of DPP-based polymers and the pathway of DPP block photodegradation is identified, thus providing guidelines for designing more stable organic absorbers.

New conjugated (BDT-TTBTBTT)n copolymers are featured as promising hole-transport materials for n–i–p perovskite solar cells delivering efficiencies of up to ∼19%.

Currently, organic small molecules represent a widely used class of hole-transport layer (HTL) materials in perovskite solar cells (PSCs). Commonly, these materials are doped to compensate for their low hole-mobility, which leads to an additional increase of the device cost along with the stability issues. An alternative approach is to use compounds containing large aromatic moieties, which can interact within the film at the intermolecular level, improving its conductivity. To demonstrate this strategy, we present four pyrene derivatives as HTL materials for perovskite solar cells. It is shown that devices fabricated using thermally evaporated films of pyrene derivatives deliver superior performance as compared to the cells with solution-processed HTLs. The power conversion efficiency of 17.9% is achieved for dopant-free perovskite solar cells using pyrene-based HTL with α-naphthylamine substituents.

One of the major challenges in the field of organic photovoltaics is associated with high-throughput manufacturing of efficient and stable organic solar cells. Practical realization of technologies for production of large-area organic solar cells requires the development of novel materials with a defined combination of properties ensuring sufficient reliability and scalability of the process in addition to good efficiency and operation stability of the devices. In this work, we designed two novel polymers comprising thiazolothiazole units and investigated their performance as absorber materials for organic solar cells and modules. Optimized small-area solar cells based on P1/[70]PCBM ([6,6]-phenyl-C71-butyric acid methyl ester) blends exhibited promising power conversion efficiency (PCE) of 7.5%, while larger area modules fabricated using slot die coating showed encouraging PCE of 4.2%. Additionally, the fabricated devices showed promising outdoor stability maintaining 60–70% of the initial efficiency after 20 sun days being exposed to natural sunlight at the Negev desert. The obtained results feature the designed polymer P1 as a promising absorber material for a large-scale production of organic solar cells under ambient conditions.

Two conjugated polymers with (X-DADAD)n backbone and 2,6- or 4,8-linked benzobisthiazole (BBT) moieties were designed, synthesized and characterized as absorber materials in thin-film organic solar cells (OSCs). The 2,6-BBT polymer (P1) delivered enhanced short circuit densities and power conversion efficiencies in OSCs compared to devices based on 4,8-BBT polymer P2. Improved photovoltaic performance is related to the optimal morphology of P1/PC71BM blend films and higher and more balanced charge carrier mobilities.

New small molecules bearing either phenylene or naphthalene core in combination with thiophene and rhodanine periphery moieties were synthesized by the Stille cross-coupling reaction. Their evaluation for prototypes of organic solar cells showed that replacing phenylene moiety by the naphthalene one caused decrease in the HOMO energy, while the open-circuit voltage and fill factors of solar cells based on these materials were significantly improved to manifest maximum power conversion efficiencies to 5.3%.

Five new donor-acceptor (X-DAD'AD)n type conjugated polymers have been synthesized using different X blocks based on carbazole, fluorene, silafluorene, benzodithiophene, and cyclopentadithiophene (CPDT). The strongly electron donating CPDT unit was used as a central D′ fragment to enhance intramolecular charge transfer interactions along the polymer backbone and reduce the bandgap of the resulting conjugated polymers. Apparently, the nature of the X block impacts the photophysical, morphological and optoelectronic properties of the designed polymers as well as their performance in bulk heterojunction solar cells. Fluorene-based copolymer P2 in combination with [70]PCBM delivered the best power conversion efficiency of 5.0% with a VOC of 0.78 V, a JSC of 11.1 mA/cm2 and a FF of 57%. Possibility for easy variation of the X and D′ blocks in the designed materials paves a way towards design of a variety of new materials for optoelectronic applications.

Conjugated polymers represent a promising family of semiconductor materials for thin-film organic solar cells (OSCs). An efficient approach to improve the photovoltaic performance of conjugated polymers is engineering the side chains attached to the polymer backbone. This work reports the impact of different alkyl substituents on the optoelectronic properties, charge carrier mobilities, thin film morphology, and photovoltaic performance of novel (X-DADAD)

The development of dopant-free organic charge transport layers is crucial for achieving long-term stability of perovskite solar cells. In this paper, we present a new polytriarylamine derivative, poly[bis(4-phenyl)(4-methylphenyl)amine] (PTA), which showed significantly improved photovoltaic performance compared to dopant-free PTAA. Perovskite solar cells based on the PTA/MoO3 hybrid hole-transport layer (HTL) and MAPbI3 absorber delivered a competitive 17.0% efficiency, which is currently the highest value achieved for n–i–p perovskite solar cells using dopant-free polytriarylamine-type HTLs. The enhanced device performance was attributed to a better HOMO alignment of PTA (5.38 eV) vs. PTAA (5.27 eV) with respect to the perovskite valence band.

We report the synthesis and extensive investigation of a broad family of novel (X-DADAD)n conjugated polymers with different X building blocks. It was shown that variation of X block in polymer backbone represents an efficient approach for tuning the polymer optical properties, frontier energy levels, charge transport characteristics as well as thin-film morphology and photovoltaic characteristics. Decent power conversion efficiencies (5.1–5.7%) were achieved for solar cells based on the polymers comprised of dibenzosilole (P2) and carbazole (P3) units. Polymers P2 and P3 showed impressive indoor and outdoor stability in solar cells while clearly outperforming common benchmark materials. In the view of the obtained results, the designed (X-DADAD)n polymers can be considered as promising semiconductor materials for stable organic photovoltaics.

A low bandgap conjugated polymer comprising benzodithiophene and diketopyrrolopyrrole units was designed and synthesized. The polymer showed an optical bandgap of ~1.3 eV and exhibited broad absorption in visible and near-infrared spectral ranges. Photodetectors based on the polymer/fullerene derivative blends were fabricated and their electrical behavior was investigated. The devices demonstrated rapid response in the infrared (λ = 850 nm) wavelengths. Photodetectors can be operated in up to 2.6 × 105 Hz frequency regime with responsivity of 42 mA W-1 and detectivity of 1.26 × 1012 Jones at λ = 850 nm and zero external bias.

We report the synthesis of novel low bandgap conjugated polymer P1 comprising thiazolothiazole, benzothiadiazole and thiophene units and investigation its photovoltaic properties in organic solar cells with [70]PCBM ([6,6]-phenyl-C71-butyric acid methyl ester) and high-performing non-fullerene IT-4F acceptor (9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2’,3’-d’]-s-indaceno [1,2-b:5,6-b’]dithiophene). Polymer P1 showed promising results in both fullerene and non-fullerene organic solar cells. In particular, P1/IT-4F blends demonstrated enhanced charge carrier mobilities and suppressed trap-assisted recombination, which resulted in impressive short-circuit current densities and decent power conversion efficiency of 8.8 % in solar cells. The fullerene-based devices delivered efficiency of 8.2 % with remarkably high open-circuit voltages. The obtained results feature conjugated polymers based on thiazolothiazole as promising absorber materials for organic solar cells.

Conjugated polymers represent a promising family of semiconductor materials for thin-film organic solar cells (OSCs). An efficient approach to improve the photovoltaic performance of conjugated polymers is engineering the side chains attached to the polymer backbone. This work reports the impact of different alkyl substituents on the optoelectronic properties, charge carrier mobilities, thin film morphology, and photovoltaic performance of novel (X-DADAD)n conjugated polymers incorporating benzo[1,2-b:4,5-b']dithiophene moieties. It has been shown that loading conjugated polymers with appropriate alkyl side chains results in a spectacular performance improvement from 6.8% to 9% in OCSs using a model fullerene acceptor [6,6]-phenyl-C71 -butyric acid methyl ester. The obtained results feature side-chain engineering as a facile and efficient strategy for designing high-performance conjugated polymers for organic photovoltaics.

High efficiencies of organic solar cells (OSCs) are generally achieved for small-area devices processed from halogenated solvents, which are hazardous to human health and pollute the environment. Commercialization of OSCs requires the development of novel photovoltaic materials, which are suitable for large-scale fabrication of devices through printable techniques using environmentally-friendly solvents. In this work, we report the synthesis of two novel polymers comprising thiazolothiazole, benzothiadiazole (P1), and benzoxadiazole (P2) moieties and the fabrication of polymer-fullerene OSCs and photovoltaic modules by blade coating under ambient conditions. The P1-based solar cells and larger area modules showed tolerance to processing solvents and delivered encouraging efficiencies illustrating polymer P1 as a promising material for environment friendly large-area photovoltaics.

Four new conjugated polymers based on benzodithiophene, thiophene and 2,1,3-benzothiadiazole or 5,6-difluoro-2,1,3-benzothiadiazole were synthesized and investigated as absorber materials for organic photovoltaics. The effect of (bi)thiophene π-spacers and fluorine substitution on the physicochemical and optoelectronic properties of the polymers was revealed and correlations were drawn with their electrical characteristics in organic solar cells. In particular, introducing either thiophene spacers or fluorine substituents does not affect much the photovoltaic performance of the polymers, while the combination of both routes was found to be a promising strategy for improving the charge carrier mobilities and morphology of the polymer-fullerene blends as well as light power conversion efficiency in solar cells based on these materials. The bulk heterojunction organic solar cells based on the π-bridged and fluorinated polymer P4 showed the highest short-circuit current density and power conversion efficiency of 7 %, which is an inspiring value for fullerene-based organic photovoltaics. Most importantly, our findings provide important insights into rational design of high-performance conjugated polymers while pursuing a combination of two efficient backbone functionalization strategies based on introduction of fluorine substituents and π-spacers to control the geometry and electronic characteristics of the polymer chains.