Improved Performance of Polymer:Polymer Solar Cells by Doping Electron‐Accepting Polymers with an Organosulfonic Acid

Abstract

The performance of polymer:polymer solar cells that are made using blend films of poly(3‐hexylthiophene) (P3HT) and poly(9,9‐dioctylfluorene‐co‐ benzothiadiazole (F8BT) is improved by doping the F8BT polymer with an organosulfonic acid [4‐ethylbezenesulfonic acid (EBSA)]. The EBSA doping of F8BT, to form F8BT‐EBSA, is performed by means of a two‐stage reaction at room temperature and 60°C with various EBSA weight ratios. The X‐ray photoelectron spectroscopy measurement reveals that both sulfur and nitrogen atoms in the F8BT polymer are affected by the EBSA doping. The F8BT‐EBSA films exhibit huge photoluminescence quenching, ionization potential shift toward lower energy, and greatly enhanced electron mobility. The short‐circuit current density of solar cells is improved by ca. twofold (10 wt.% EBSA doping), while the open‐circuit voltage increases by ca. 0.4 V. Consequently, the power conversion efficiency was improved by ca. threefold, even though the optical density of the P3HT:F8BT‐EBSA blend film is reduced by 10 wt.% EBSA doping due to the nanostructure and surface morphology change.

Organic nonvolatile memory transistors with self-doped polymer energy well structures

“…The measured onset value was B5.4 eV, which corresponds to B5.7 eV after calibration. [21][22][23] To measure the conductivity of the SD-PARA film in the out-of-plane direction, we fabricated a diode device in which the SD-PARA film was sandwiched between the bottom and top electrodes (see details in the experimental section). The current density-voltage (J-V) curves revealed that the SD-PARA film is not a perfect conductor but a semiconductor because of its diode-like shape and the asymmetric current density trend between the forward and reverse biases (see the inset in Figure 1c).…”

Three-fold improvement in the performance of all-polymer photovoltaic devices with graphene

“…Nevertheless, blend performance is poor, with efficiencies of 0.13% when fabricated from p-xylene using a 60:40 weight ratio [13]. Efficiency was improved when processed using a solvent additive [14], by annealing [15], or by the addition of P3HT nanofibers [16].…”

Effect of halogen-terminated additives on the performance and the nanostructure of all-polymer solar cells

“…Of the various factors affecting the poor stability of polymer:fullerene solar cells, the intrinsic nature of fullerene derivatives has been an issue because their derivatives are basically small molecules that are vulnerable to recrystallization under continuous illumination with solar light (energy) [21][22][23][24][25]. Hence, all-polymer solar cells, where electron-accepting component is composed of an electron-accepting polymer instead of fullerenes so that the recrystallization issue * E-mail: ykimm@knu.ac.kr; Fax: +82-53-950-6615 can be resolved, have been intensively studied by major research groups [2,[26][27][28][29][30][31][32]. However, the performance of all-polymer solar cells is still much poorer than that of polymer:fullerene solar cells, which can be ascribed to the large charge-blocking resistance in the polymer:polymer BHJ films owing to the intimate mixing of the two (ptype and n-type) polymers [26].…”

“…However, the performance of all-polymer solar cells is still much poorer than that of polymer:fullerene solar cells, which can be ascribed to the large charge-blocking resistance in the polymer:polymer BHJ films owing to the intimate mixing of the two (ptype and n-type) polymers [26]. Various approaches, including thermal annealing, use of co-solvents, nanomolding, additives, etc., have been tried to overcome this problem [26][27][28][29][30][31][32][33].…”