An Operando Study on the Photostability of Nonfullerene Organic Solar Cells

Abstract

Nonfullerene organic solar cells (OSCs) have achieved an impressive power conversion efficiency (PCE) over the past few years, showing a great potential for real applications. However, the study on the photostability and degradation mechanism of nonfullerene OSCs is far behind than that of fullerene‐based solar cells, which is crucial for the commercial applications of the technology. Herein, an efficient and stable nonfullerene OSC based on PCE10:rhodanine‐benzothiadiazole‐coupled indacenodithiophene with branched 2‐ethylhexyl side chains (EH‐IDT) is fabricated from environmentally benign solvent. The PCE10:EH‐IDT solar cell shows a high PCE of 9.17% and a long operational lifetime (T80) of 2132 h, compared with other two OSCs based on 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone)‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2’,3’‐d’]‐s‐indaceno[1,2‐b:5,6‐b’]‐dithiophene (ITIC) and another fuse ring acceptor with withdrawing units of 1,1‐dicyanomethylene‐3‐indanone and hexyl side chains (IDIC) nonfullerene acceptors, with tested lifetimes of only 221 and 558 h, respectively. As indicated by the Flory–Huggins interaction parameters, ITIC and IDIC have poor miscibility with PCE10, which leads to morphology degradation, suppressed charge generation, increased trap states, and charge recombination in the photoaging test, which accounts for the significant loss of short‐circuit current density and fill factor during operation. The improved miscibility of the donor and the acceptor results in a more stable morphology, and the PCE10:EH‐IDT solar cells thus achieve an outstanding overall performance that combines high efficiency and superior photostability and paves the way for the potential practical applications of OSCs.

Unraveling the Microstructure‐Related Device Stability for Polymer Solar Cells Based on Nonfullerene Small‐Molecular Acceptors

“…Most of the stability studies so far have been focused on fullerene‐based OSCs, [ 7–10 ] while for unstable NFA‐based OSCs, understanding of the degradation mechanism is still limited. For NFA‐based systems, promising photostability has been demonstrated for many‐systems including P3HT:IDTBR, [ 11 ] PCE10 with EH‐IDTBR, [ 12 ] or IEICO‐4F, [ 13 ] PffBT4T‐2OD:EH‐IDTBR, [ 14 ] single‐component devices [ 15 ] as well as ITIC derivatives. [ 4,16 ] However, studies up to date indicated that the light stability of NFA systems is strongly materials‐dependent.…”

Interface-enhanced organic solar cells with extrapolated T80 lifetimes of over 20 years

“…For photostability testing, the devices were encapsulated with a glass cover in a glove box maintained under a dry N 2 atmosphere to exclude possible photochemical degradation effects caused by the presence of oxygen and moisture. Light exposure was performed using a LED source with an illumination wavelength that ranged from 380 to 1000 nm and an illumination equivalent of 1 sun [19]. The luminescent spectrum of the LED is presented in Fig.…”

“…Given this importance, more and more studies have attempted to address the photostability issues associated with NFA-based OSCs, with major efforts focused on identifying donor/acceptor systems that display enhanced morphological stability [16][17][18]. As part of these efforts, we have reported recently that donor/acceptor pairs with good miscibility can achieve stable morphologies with enhanced photostability, and allow for OSC operating lifetimes (T 80 ) of over 2000 h [19]. Similarly, in a recent study, Du and coworkers [13] reported an efficient OSC based on a PBDB-T donor and an ITIC-2F acceptor with a PCE of 8% and a T 80 lifetime of 11,000 h. These values represent one of the best reported stability results for OSCs in the literature.…”

A Cost‐Effective, Aqueous‐Solution‐Processed Cathode Interlayer Based on Organosilica Nanodots for Highly Efficient and Stable Organic Solar Cells

“…[11][12][13][14][15] On the one hand, the stability related to the microstructure of a bulkheterojunction (BHJ) photoactive layer is essential for long-term stability; on the other hand, the stability of interface materials and the compatibility between the photoactive layer and the interface layer play a key role in determining efficiency and stability of OSCs. [16][17][18][19][20] By tuning the properties of the photoactive layer, such as tailoring the chemical structure of both donor (D) and acceptor (A), or incorporating a "phase compatibilizer" or "molecular lock" between D/A components, the microstructure stability of BHJ photoactive layer could be addressed. [21][22][23][24][25] However, interface-associated device's instability is less frequently investigated and analyzed for state-of-the-art OSCs.…”