Open‐Cage Fullerenes as n‐Type Materials in Organic Photovoltaics: Relevance of Frontier Energy Levels, Carrier Mobility and Morphology of Different Sizable Open‐Cage Fullerenes with Power Conversion Efficiency in Devices

Abstract

Organic bulk heterojunction (OBHJ) photovoltaics, incorporating open‐cage fullerenes with orifice‐size of 8, 12, 13, 16 and 20‐membered‐rings as n‐type materials, display power conversion efficiency (PCE) up to 2.9% by the 8‐membered‐ring fullerene under AM 1.5G irradiation; their PCEs decrease as the orifice‐size of open‐cage fullerene increases, primarily due to electron‐mobility descends as the cage is ruptured to larger holes.

n‐Channel Organic Semiconductors Derived from Air‐Stable Four‐Coordinate Boron Complexes of Substituted Thienylthiazoles

“…Redox potentials of the compounds were measured by cyclic voltammetry (CV) in CH 2 Cl 2 in the presence of Bu 4 NPF 6 as as upportinge lectrolyte and calibrated versusf errocenium/ferrocene (Fc + /Fc). [24] Furthermore, the reversible reduction processes of indandione derivative 7b are cathodically shifted versus potentials of 7a to À1.12, and À1.49 V, which implies that reduction is more feasible in less electron-rich 7a.T he more pronounced modulation of electron density in A-p-A compounds was achieved upon substitution of the boryl core with strongly electron-accepting DCIND substituents. Molecule 7a bearing two dicyanomethylene groups undergoes two reversible reduction processes at À1.00 and À1.25 V. These potentials are comparable to the reduction potentials of ac ore-unsubstituted perylenebisimide (À0.95, À1.15 V) whichw as successfully applied as an n-type semiconducting material, [23] and correspond well with the position of the LUMO of fullerenes (À3.8 to À4.3 eV).…”

Organic photovoltaic cells: Novel organic semiconducting materials and molecular arrangement engineering

“…In 1992, Sariciftci et al [29] firstly reported that C 60 could efficiently quench MEH-PPV emissions by photoinduced electron transfer from the excited state of a conducting polymer onto buckminsterfullerene, C 60 , and related phenomena are not limited to MEH-PPV. After that, different structures of fullerene and its derivatives with various energy level alignment were doped into the polymer for high efficiently photoinduced electron transfer from the excited state of organic semiconducting materials [30][31][32][33][34][35][36][37]. These fullerene derivatives have many advantages in photovoltaic cells, including a deep-lying LUMO (~3.8-4.2 eV) for effective charge separation between the electron donor and acceptor, reversible reduction with ability to accept up to six electrons, ultra-fast three dimensional charge transfer, and high electron mobility.…”

“…A series of fullerene derivatives with different diameter cage from C 70 to C 84 were used as electron acceptors in bulk heterojunction polymer-fullerene solar cells [32][33][34][35][36][37]. These fullerene derivatives have many advantages in photovoltaic cells, including a deep-lying lowest unoccupied molecular orbital (LUMO, ~3.8-4.2 eV) for the effective charge separation between the electron donor and acceptor, reversible reduction with ability to accept up to six electrons, ultra-fast three dimensional charge transfer, and high electron mobility.…”

“…What's more, some in-depth modification has been applied on the C 60 itself. Chen et al [35] synthesized a series of open-cage fullerenes possessing suitable solubilizing functionality with a variety of frontier molecular orbital energy levels and carrier mobility as n-type materials. Their experimental results pointed out a new direction of effective electron acceptor materials.…”

“…One of the main challenges faced by the OPV community is Figure 2 Chemical structures of typical electron withdrawing materials [28,30,32,35,37,38]. the synthesis of narrow band gap semiconducting materials which can harvest more photon from sunlight.…”