Mastering morphology of non-fullerene acceptors towards long-term stable organic solar cells

Abstract

Despite the rapid progress of organic solar cells based on non-fullerene acceptors, simultaneously achieving high power conversion efficiency and long-term stability for commercialization requires sustainable research effort. Here, we demonstrate stable devices by integrating a wide bandgap electron-donating polymer (namely PTzBI-dF) and two acceptors (namely L8BO and Y6) that feature similar structures yet different thermal and morphological properties. The organic solar cell based on PTzBI-dF:L8BO:Y6 could achieve a promising efficiency of 18.26% in the conventional device structure. In the inverted structure, excellent long-term thermal stability over 1400 h under 85 °C continuous heating is obtained. The improved performance can be ascribed to suppressed charge recombination along with appropriate charge transport. We find that the morphological features in terms of crystalline coherence length of fresh and aged films can be gradually regulated by the weight ratio of L8BO:Y6. Additionally, the occurrence of melting point decrease and reduced enthalpy in PTzBI-dF:L8BO:Y6 films could prohibit the amorphous phase to cluster, and consequently overcome the energetic traps accumulation aroused by thermal stress, which is a critical issue in high efficiency non-fullerene acceptors-based devices. This work provides insight into understanding non-fullerene acceptors-based organic solar cells for improved efficiency and stability.

Boosting electron transport in non-fullerene acceptors using non-chlorinated solvents

“…For example, O -IDTBR yields high-performance TFTs when processed from chlorobenzene (CB) solutions, whereas L8-BO exhibits optimal charge transport when cast from chloroform (CF) solutions. 36–41 To investigate the possibility of using more eco-friendly solvents, we selected various non-chlorinated solvents, including anisole (ANI), mesitylene (MES), toluene (TOL), and o -xylene (XYL) (see Fig. 1b) to dissolve both NFAs.…”

Dredging photocarrier trapping pathways via “charge bridge” driven exciton–phonon decoupling enables efficient and photothermal stable quaternary organic solar cells

“…12–14 Depending on the degraded microstructure, singlet excitons in nanoscale spatial region might control light emission and undergo a large number of non-radiative processes, such as diffusion, annihilation, localization into trap states, and dissociation into charge carriers. Quite recently, some feasible strategies such as constructing a multiple-component photoactive layer based on one-pot polymerization, 15 combining NFAs with a similar structure yet different morphological features, 16 designing oligomer molecules and polymer acceptors, 17–19 and employing solid additives 20,21 have been proposed to overcome this conundrum related to the metastable morphology. The recent progress made in revealing the degradation mechanism and improving the device lifetime of the state-of-the-art OSCs under various aging conditions is summarized in Table S1 (ESI†).…”

Unraveling the Impact of Thickness on Active Layer Morphology and Device Performance of Semitransparent Organic Solar Cells: A Comprehensive Study

“…A disordered or phase-separated morphology of the active layer can result in inefficient charge transport and reduced device performance. 21,22 Furthermore, the layer needs a well-organized and interconnected network of donor and acceptor domains to efficiently separate the photogenerated charges and transport them to the respective electrodes. 23−25 The active layer was deposited using solution-processed techniques, such as spin coating and doctor blade coating, in the BHJ OSCs.…”

“…Since a BHJ device comprises numerous layers, one on top of the other, the light should be maximally collected at the active layer after undergoing all the optical phenomena through the subsequent layers. A disordered or phase-separated morphology of the active layer can result in inefficient charge transport and reduced device performance. , Furthermore, the layer needs a well-organized and interconnected network of donor and acceptor domains to efficiently separate the photogenerated charges and transport them to the respective electrodes. – …”