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Hole‐collecting monolayers have greatly advanced the development of positive‐intrinsic‐negative perovskite solar cells (p‐i‐n PSCs). To date, however, most of the anchoring groups in the reported monolayer materials are designed to bind to the transparent conductive oxide (TCO) surface, resulting in less availability for other functions such as tuning the wettability of the monolayer surface. In this work, we developed two anchorable molecules, 4PATTI‐C3 and 4PATTI‐C4, by employing a saddle‐like indole‐fused cyclooctatetraene as a π‐core with four phosphonic acid anchoring groups linked through propyl or butyl chains. Both molecules form monolayers on TCO substrates. Thanks to the saddle shape of a cyclooctatetraene skeleton, two of the four phosphonic acid anchoring groups were found to point upward, resulting in hydrophilic surfaces. Compared to the devices using 4PATTI‐C4 as the hole‐collecting monolayer, 4PATTI‐C3‐based devices exhibit a faster hole‐collection process, leading to higher power conversion efficiencies of up to 21.7 % and 21.4 % for a mini‐cell (0.1 cm2) and a mini‐module (1.62 cm2), respectively, together with good operational stability. This work represents how structural modification of multipodal molecules could substantially modulate the functions of the hole‐collecting monolayers after being adsorbed onto TCO substrates. [ABSTRACT FROM AUTHOR]

Hole‐collecting monolayers have greatly advanced the development of positive‐intrinsic‐negative perovskite solar cells (p‐i‐n PSCs). To date, however, most of the anchoring groups in the reported monolayer materials are designed to bind to the transparent conductive oxide (TCO) surface, resulting in less availability for other functions such as tuning the wettability of the monolayer surface. In this work, we developed two anchorable molecules, 4PATTI‐C3 and 4PATTI‐C4, by employing a saddle‐like indole‐fused cyclooctatetraene as a π‐core with four phosphonic acid anchoring groups linked through propyl or butyl chains. Both molecules form monolayers on TCO substrates. Thanks to the saddle shape of a cyclooctatetraene skeleton, two of the four phosphonic acid anchoring groups were found to point upward, resulting in hydrophilic surfaces. Compared to the devices using 4PATTI‐C4 as the hole‐collecting monolayer, 4PATTI‐C3‐based devices exhibit a faster hole‐collection process, leading to higher power conversion efficiencies of up to 21.7 % and 21.4 % for a mini‐cell (0.1 cm2) and a mini‐module (1.62 cm2), respectively, together with good operational stability. This work represents how structural modification of multipodal molecules could substantially modulate the functions of the hole‐collecting monolayers after being adsorbed onto TCO substrates. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate that the dimerization behavior of amine-substituted dicyanomethyl radicals can be switched from σ- to π-dimerization simply by varying the electron-donating substituents. For dicyanomethyl radicals with a 4,4′-ditolylamine ( DT.) or a phenothiazine ( PT.) substituent, the monomeric radical form and the corresponding dimer connected by a reversible C−C bond (σ-dimer) are in equilibrium in solution. On the other hand, the radical with the julolidine skeleton ( JD.) does not undergo σ-dimerization and was isolated as a stable radical in spite of the absence of bulky protecting groups. X-ray single-crystal analysis revealed that JD. forms the π-dimer in the crystalline state, and variable-temperature spectroscopy showed that JD. is in equilibrium with the π-dimer in toluene solution. DFT calculations point to the importance of electrostatic interactions as a driving force for the π-dimerization of JD. because of its polarized structure. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate that the dimerization behavior of amine-substituted dicyanomethyl radicals can be switched from σ- to π-dimerization simply by varying the electron-donating substituents. For dicyanomethyl radicals with a 4,4′-ditolylamine ( DT.) or a phenothiazine ( PT.) substituent, the monomeric radical form and the corresponding dimer connected by a reversible C−C bond (σ-dimer) are in equilibrium in solution. On the other hand, the radical with the julolidine skeleton ( JD.) does not undergo σ-dimerization and was isolated as a stable radical in spite of the absence of bulky protecting groups. X-ray single-crystal analysis revealed that JD. forms the π-dimer in the crystalline state, and variable-temperature spectroscopy showed that JD. is in equilibrium with the π-dimer in toluene solution. DFT calculations point to the importance of electrostatic interactions as a driving force for the π-dimerization of JD. because of its polarized structure. [ABSTRACT FROM AUTHOR]