A Paradigmatic Change: Linking Fullerenes to Electron Acceptors

The potential of Lu₃N@C₈₀ and its analogues as electron acceptors in the areas of photovoltaics and artificial photosynthesis is tremendous. To this date, their electron-donating properties have never been explored, despite the facile oxidations that they reveal when compared to those of C₆₀. Herein, we report on the synthesis and physicochemical studies of a covalently linked Lu₃N@C₈₀–perylenebisimide (PDI) conjugate, in which PDI acts as the light harvester and the electron acceptor. Most important is the unambiguous evidencein terms of spectroscopy and kineticsthat corroborates a photoinduced electron transfer evolving from the ground state of Lu₃N@C₈₀ to the singlet excited state of PDI. In stark contrast, the photoreactivity of a C₆₀–PDI conjugate is exclusively governed by a cascade of energy-transfer processes. Also, the electron-donating property of the Lu₃N@C₈₀ moiety was confirmed through constructing and testing a bilayer heterojunction solar cell device with a PDI and Lu₃N@C₈₀ derivative as electron acceptor and electron donor, respectively. In particular, a positive photovoltage of 0.46 V and a negative short circuit current density of 0.38 mA are observed with PDI/Ca as anode and ITO/Lu₃N@C₈₀ as cathode. Although the devices were not optimized, the sign of the <i>V</i>_OC and the flow direction of <i>J</i>_SC clearly underline the unique oxidative role of Lu₃N@C₈₀ within electron donor–acceptor conjugates toward the construction of novel optoelectronic devices

Two Similar Near-Infrared (IR) Absorbing Benzannulated Aza-BODIPY Dyes as Near-IR Sensitizers for Ternary Solar Cells

Ternary composite inverted organic solar cells based on poly­(3-hexylthiophen-2,5-diyl) (P3HT) and phenyl-C₆₁-butyric acid methyl ester (PCBM) blended with two different near-infrared absorbing benzannulated aza-BODIPY dyes, difluoro-bora-bis-(1-phenyl-indoyl)-azamethine (<b>1</b>) or difluoro-bora-bis-(1-(5-methylthiophen)-indoyl)-azamethine (<b>2</b>), were constructed and characterized. The amount of these two aza-BODIPY dyes, within the P3HT and PCBM matrix, was systematically varied, and the characteristics of the respective devices were recorded. Although the addition of both aza-BODIPY dyes enhanced the absorption of the blends, only the addition of <b>1</b> improved the overall power conversion efficiency (PCE) in the near-infrared (IR) region. The present work paves the way for the integration of near-infrared absorbing aza-BODIPY derivatives as sensitizers in ternary composite solar cells

A Paradigmatic Change: Linking Fullerenes to Electron Acceptors

The potential of Lu₃N@C₈₀ and its analogues as electron acceptors in the areas of photovoltaics and artificial photosynthesis is tremendous. To this date, their electron-donating properties have never been explored, despite the facile oxidations that they reveal when compared to those of C₆₀. Herein, we report on the synthesis and physicochemical studies of a covalently linked Lu₃N@C₈₀–perylenebisimide (PDI) conjugate, in which PDI acts as the light harvester and the electron acceptor. Most important is the unambiguous evidencein terms of spectroscopy and kineticsthat corroborates a photoinduced electron transfer evolving from the ground state of Lu₃N@C₈₀ to the singlet excited state of PDI. In stark contrast, the photoreactivity of a C₆₀–PDI conjugate is exclusively governed by a cascade of energy-transfer processes. Also, the electron-donating property of the Lu₃N@C₈₀ moiety was confirmed through constructing and testing a bilayer heterojunction solar cell device with a PDI and Lu₃N@C₈₀ derivative as electron acceptor and electron donor, respectively. In particular, a positive photovoltage of 0.46 V and a negative short circuit current density of 0.38 mA are observed with PDI/Ca as anode and ITO/Lu₃N@C₈₀ as cathode. Although the devices were not optimized, the sign of the <i>V</i>_OC and the flow direction of <i>J</i>_SC clearly underline the unique oxidative role of Lu₃N@C₈₀ within electron donor–acceptor conjugates toward the construction of novel optoelectronic devices