Recent Developments in the Optimization of the Bulk Heterojunction Morphology of Polymer: Fullerene Solar Cells

Abstract

Organic photovoltaic (OPV) devices, made with semiconducting polymers, have recently attained a power conversion efficiency (PCE) over 14% in single junction cells and over 17% in tandem cells. These high performances, together with the suitability of the technology to inexpensive large-scale manufacture, over lightweight and flexible plastic substrates using roll-to-roll (R2R) processing, place the technology amongst the most promising for future harvesting of solar energy. Although OPVs using non-fullerene acceptors have recently outperformed their fullerene-based counterparts, the research in the development of new fullerenes and in the improvement of the bulk-heterojunction (BHJ) morphology and device efficiency of polymer:fullerene solar cells remains very active. In this review article, the most relevant research works performed over the last 3 years, that is, since the year 2016 onwards, in the field of fullerene-based polymer solar cells based on the copolymers PTB7, PTB7-Th (also known as PBDTTT-EFT) and PffBT4T-2OD, are presented and discussed. This review is primarily focused on studies that involve the improvement of the BHJ morphology, efficiency and stability of small active area devices (typically < 15 mm2), through the use of different processing strategies such as the use of different fullerene acceptors, different processing solvents and additives and different thermal treatments.

Amplified Spontaneous Emission and Optical Gain in Organic Single Crystal Quinquethiophene

“…Organic semiconductors have received significant attention from researchers and scientists due to their potential applications in various electronic and optoelectronic devices such as organic light emitting diodes (OLEDs) [1][2][3], organic light emitting field effect transistors (OLEFETs) [4,5], organic photovoltaics (OPV) [6,7], and organic field effect transistors (OFETs) [8,9]. A few of the interesting characteristics of organic semiconductors are their low cost, low temperature processability, light weight, mechanical flexibility, and solubility in various organic solvents [10][11][12].…”

PffBT4T-2OD Based Solar Cells with Aryl-Substituted N-Methyl-Fulleropyrrolidine Acceptors

“…To overcome these drawbacks many efforts were made to develop several third-generation thin-film solar technologies. As an example, organic photovoltaic cells (OPVs) [1][2][3][4][5] can be low-cost production since they can be manufactured in larger areas on flexible and lightweight plastic substrates via solution and printed using high-throughput roll-to-roll methods (R2R) [6]. In recent years, the OPVs have experienced significant developments in power conversion efficiency (PCE), attaining recently over 16% for single-junction devices [7][8][9] and PCE over 17% for tandem cells [10].…”

Towards Highly Efficient TADF Yellow-Red OLEDs Fabricated by Solution Deposition Methods: Critical Influence of the Active Layer Morphology

“…Some of these issues need further investigation. In solution-processed organic devices, the solvent plays a critical role in the device performance, where the viscosity, temperature, and evaporation rate of solvent control the electrical properties of the thin film [30][31][32][33][34][35]. A non-aromatic solvent such as chloroform (CF), with a high evaporation rate, or an aromatic solvent like chlorobenzene (CB) or dichlorobenzene (DCB), with a low evaporation rate, can be employed to study device characteristics, and exploiting these properties could be an effective route to change the electrical and optical properties of the device [34].…”