Polymer Photovoltaic Cells Based on Solution‐Processable Graphene and P3HT

Abstract

A soluble graphene, which has a one‐atom thickness and a two‐dimensional structure, is blended with poly(3‐hexylthiophene) (P3HT) and used as the active layer in bulk heterojunction (BHJ) polymer photovoltaic cells. Adding graphene to the P3HT induces a great quenching of the photoluminescence of the P3HT, indicating a strong electron/energy transfer from the P3HT to the graphene. In the photovoltaic devices with an ITO/PEDOT:PSS/P3HT:graphene/LiF/Al structure, the device efficiency increases first and then decreases with the increase in the graphene content. The device containing only 10 wt % of graphene shows the best performance with a power conversion efficiency of 1.1%, an open‐circuit voltage of 0.72 V, a short‐circuit current density of 4.0 mA cm−2, and a fill factor of 0.38 under simulated AM1.5G conditions at 100 mW cm−2 after an annealing treatment at 160 °C for 10 min. The annealing treatment at the appropriate temperature (160 °C, for example) greatly improves the device performance; however, an annealing at overgenerous conditions such as at 210 °C results in a decrease in the device efficiency (0.57%). The morphology investigation shows that better performance can be obtained with a moderate content of graphene, which keeps good dispersion and interconnection. The functionalized graphene, which is cheap, easily prepared, stable, and inert against the ambient conditions, is expected to be a competitive candidate for the acceptor material in organic photovoltaic applications.

Graphene/polymer composites for energy applications

“…An OPV based on the hybrid of graphene and poly(3-hexylthiophene) (P3HT) was also fabricated and annealed. 108 It exhibited a PCE of 1.1%, open circuit voltage of 0.72 V, a short circuit current density of 4.0 mA cm À2 , and a FF of 0.38 upon excitation with AM 1.5 simulated sunlight at 100 mW cm À2 . The efficiencies are still far from those of the state-of-the-art OPVs, possibly because of the irregular molecular structure of rGO; however, graphene-based cells exhibited higher efficiencies than most of the best OPVs based on other alternative acceptor materials to C60 derivatives.…”

“…As a novel and unique member of the carbon nanomaterials family, graphene is an attractive material for fabricating transparent electrodes 27,43,141 and improving the performances of dyesensitized 15,142,143 and heterojunction solar cells. [108][109][110] Transparent Conducting Electrodes TCEs are a key component of optoelectronic devices. The ideal TECs should possess high transparency (>80%), low resistance (<100 X/&), and an appropriate work function (4.5-5.2 eV).…”

Nanoscale assembly into extended and continuous structures and hybrid materials

“…PCEs as high as 1.4% at 10 wt% FCCG in P3HT or poly-3-octylthiophene were obtained. 121,122 The importance of annealing was established definitively, with PCE improving from 0.15 to 1.1%. Remarkably, the observed open circuit voltage was higher than predicted theoretically, suggesting that the work function of FCCG differs from that of pristine graphene.…”

“…Scanning electron microscopy characterization of the thin film showed continuous pathways for electron transport at 10 wt% GO in the active layer, and platelet orientation parallel to the underlying substrate (and thus the electrodes) prevented short circuiting. 122,123 Phenyl-functionalized GO (10 wt%) has also been blended with a P3HT/PC 60 BM composite (1:1) in attempts to bridge fullerene domains and provide continuous pathways for electron transport. After thermal annealing of devices at 160 1C, to reduce GO to FCCG and generate polymer fibrils, a PCE of 1.4% was obtained, compared with 0.88% PCE without FCCG.…”

Unique synthesis of graphene-based materials for clean energy and biological sensing applications

“…It has been reported that graphene-based materials and composites can be used as transparent electrodes [90,91] and electron acceptors in PSCs [92][93][94][95].…”