Abstract
In this review paper, we present a comprehensive summary of the different organic solar cell (OSC) families. Pure and doped conjugated polymers are described. The band structure, electronic properties, and charge separation process in conjugated polymers are briefly described. Various techniques for the preparation of conjugated polymers are presented in detail. The applications of conductive polymers for organic light emitting diodes (OLEDs), organic field effect transistors (OFETs), and organic photovoltaics (OPVs) are explained thoroughly. The architecture of organic polymer solar cells including single layer, bilayer planar heterojunction, and bulk heterojunction (BHJ) are described. Moreover, designing conjugated polymers for photovoltaic applications and optimizations of highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy levels are discussed. Principles of bulk heterojunction polymer solar cells are addressed. Finally, strategies for band gap tuning and characteristics of solar cell are presented. In this article, several processing parameters such as the choice of solvent(s) for spin casting film, thermal and solvent annealing, solvent additive, and blend composition that affect the nano-morphology of the photoactive layer are reviewed.
Highlights
In the past few decades, a large increase in energy demand to use fossil energy resources, regarding their storage deficiency and environmental impact, has become a worldwide energy issue [1].Collecting energy from daylight by photovoltaic technologies is considered to be one of the best imperative techniques to overcome increasing global energy demand [2]
In 2002, a bulk heterojunction (BHJ) solar cell based on P3HT:PC61 BM was fabricated and exhibited a maximum Jsc of 8.7 mA cm−2, which corresponded to very high external quantum efficiency (EQE) above 75% at the absorption peak
Li et al reported a new bis-adduct fullerene derivative (IC60 BA) with stronger absorbance in the visible region compared to PC61 BM, and the lowest unoccupied molecular orbital (LUMO) level of IC60 BA upshifted to −3.74 eV, which was higher than PC61 BM [288]
Summary
In the past few decades, a large increase in energy demand to use fossil energy resources, regarding their storage deficiency and environmental impact, has become a worldwide energy issue [1]. Conjugated polymers are broadly employed in fabricating organic solar cells (OSCs). Polymer-based solar cells have been the topic of more emphasis and continuous study in recent decades, which have shown a substantial increase in PCEs from 6% to 17% [23,24,25,26,27,28,29]. In BHJ polymer solar cells, the active layer is composed of a low band gap conjugated polymer as the donor and fullerene/non-fullerene derivatives as an electron acceptor. Noteworthy efforts have been made to narrow the polymer donor band gap so as to use the infrared photons, which caused the development of PCE from 5% to 12% in about a decade. Various applications based on conjugated polymers, including optoelectronic devices and organic solar cells, are discussed
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