Enhanced dissociation of excitons and charge transfer in organic solar cells of polymer:fullerene blends with molecular BPFZn doping

Abstract

We introduce bis(pentafluorophenyl)zinc (BPFZn) as a molecular dopant in an organic solar cell (OSC) system based on polymer:fullerene blends to improve the efficiency of exciton dissociation and balance charge-carrier mobilities. We employ PC 71 BM as an acceptor along with PTB7-Th as a donor to form bulk heterojunctions. The maximum power conversion efficiency increases from 7.7% without doping to 8.7% upon BPFZn doping at a concentration of 0.01 wt %. The fill factor, which is increased from 50.7% to 57.8%, is the main device parameter of enhancement. An optimal concentration of BPFZn promotes splitting of exciton and suppresses charge recombination in the PTB7-Th:PC 71 BM OSCs. Additionally, balanced carrier mobilities are observed in the moderately doped blends.

Extraction of charge transfer states dissociation probability and localised states parameters for PTB7-Th:PC71BM photovoltaic cells: using experimental J-V curves

“…Hence NGR is another factor that determines the performance of OPV devices. The rate of NGR is mathematically described by equation (12) [36]…”

“…The energy offsets at the donor-acceptor (D:A) interfaces are generally greater than the exciton binding energy, facilitating the formation of charge transfer states (CTS) at interfaces. The CTS are then dissociate into the free charge carriers (electrons and holes) [11,12]. The binding energy of excitons (0.5 eV or higher), depends on the chemical properties of the organic molecules and their environment [13].…”

“…The binding energy of excitons (0.5 eV or higher), depends on the chemical properties of the organic molecules and their environment [13]. The formation of the CTS is hindered by the decay of excitons to the ground state, resulting in the recombination of bound electron-hole pairs and reduced photocurrent density [11,12,[14][15][16][17]. Extensive research efforts have been devoted to enhance the exciton conversion efficiency in order to achieve higher current and voltage output, leading to improved power conversion efficiency (PCE).…”

Poly(ethylene glycol)–Fullerene Composite Films and Free-Standing Nanosheets for Flexible Electronic Devices and Sensors

“…Fullerene (C60) is a unique carbon allotrope consisting of 60 carbon atoms with sp 2 hybridization which form a spherical structure composed of 12 pentagons and 20 hexagons in icosahedral symmetry . Due to its distinguished physicochemical properties, C60 and its derivatives attract significant attention of scientific and industrial communities, − above all in the context of organic electronics and photovoltaics, − photodetectors, − and sensor fabrication. − Along with C60, C60-based composites are useful as well, representing a large variety of multi-functional materials with different compositions, structures, morphologies, and properties. , As a representative example, C60–polymer composites can be mentioned, , serving, in particular, as active materials for such applications as electrochemical sensors − and organic solar cells. − …”

Discovery of versatile bat‐shaped acceptor materials for high‐performance organic solar cells ‐ a DFT approach

“…13 Silicone-based inorganic photovoltaic materials 7,14 has also been used due to their enhanced PCEs, which are being replaced by OSCs owing to their higher optical absorption coefficient, modified surface morphology, easier and cost-effective synthetic protocols. 13,15 Numerous small-sized organic compounds, 16,17 organic polymers with conjugated π-system, 18,19 and inorganic metallic oxides 18 are reported to be efficient holetransporting agents 20 in photovoltaic materials.…”