Asymmetrically Substituted 10H,10'H-9,9'-Spirobi[acridine] Derivatives as Hole-Transporting Materials for Perovskite Solar Cells.

Hole-transporting materials (HTMs) based on the 10H, 10'H-9,9'-spirobi [acridine] core (BSA50 and BSA51) were synthesized, and their electronic properties were explored. Experimental and theoretical studies show that the presence of rigid 3,6-dimethoxy-9H-carbazole moieties in BSA 50 brings about improved hole mobility and higher work function compared to bis(4-methoxyphenyl)amine units in BSA51, which increase interfacial hole transportation from perovskite to HTM. As a result, perovskite solar cells (PSCs) based on BSA50 boost power conversion efficiency (PCE) to 22.65 %, and a PSC module using BSA50 HTM exhibits a PCE of 21.35 % (6.5×7 cm) with a Voc of 8.761 V and FF of 79.1 %. The unencapsulated PSCs exhibit superior stability to devices employing spiro-OMeTAD, retaining nearly 90 % of their initial efficiency after 1000 h operation output. This work demonstrates the high potential of molecularly engineered spirobi[acridine] derivatives as HTMs as replacements for spiro-OMeTAD.

Methoxydiphenylamine-substituted fluorene derivatives as hole transporting materials: role of molecular interaction on device photovoltaic performance.

The molecular structure of the hole transporting material (HTM) play an important role in hole extraction in a perovskite solar cells. It has a significant influence on the molecular planarity, energy level, and charge transport properties. Understanding the relationship between the chemical structure of the HTM's and perovskite solar cells (PSCs) performance is crucial for the continued development of the efficient organic charge transporting materials. Using molecular engineering approach we have constructed a series of the hole transporting materials with strategically placed aliphatic substituents to investigate the relationship between the chemical structure of the HTMs and the photovoltaic performance. PSCs employing the investigated HTMs demonstrate power conversion efficiency values in the range of 9% to 16.8% highlighting the importance of the optimal molecular structure. An inappropriately placed side group could compromise the device performance. Due to the ease of synthesis and moieties employed in its construction, it offers a wide range of possible structural modifications. This class of molecules has a great potential for structural optimization in order to realize simple and efficient small molecule based HTMs for perovskite solar cells application.

Heteroleptic Ru(ii)-bipyridine complexes based on hexylthioether-, hexyloxy- and hexyl-substituted thienylenevinylenes and their application in dye-sensitized solar cells.

A series of eight Ru(ii) heteroleptic complexes incorporating an ancillary [2,2']bipyridine functionalised at the [4,4'] positions with one (-type) or two (-type) thienylenevinylenes (nTVs, n = 2 or 4) is reported. Three types of substitutions have been used for nTVs: hexylthioether, hexyloxy and hexyl. The characterisation of the half-sandwich intermediates and final complexes is provided. In particular, the half-sandwich complexes in the -type series are obtained as a racemate, whereas the heteroleptic complexes consist of two regioisomers. Finally, these complexes have been tested as dyes in dye-sensitized solar cells (DSSCs). Counterintuitively, better performances were obtained for -type complexes with shorter 2TV moieties. The best performing dye was the Ru(ii) complex mono-functionalized with a 2TV moiety having an hexylthioether substitution (), which achieved a maximum power efficiency of 2.77% under full sun illumination (AM1.5G standard conditions). The structure-performance relationship in DSSCs is discussed based on photovoltaic and electrochemical data and DFT-calculations.