Layer‐by‐layered organic solar cells: Morphology optimizing strategies and processing techniques

Abstract

The last decades have witnessed the rapid development and the gradually improved efficiencies of organic solar cells (OSCs), which show great potentials in the fabrication of eco-friendly and flexible photovoltaic panels. Layer-by-layered (LBL) structure via sequential processing of the donor and acceptor layers becomes an advisable option to construct pseudo-bilayer configurations in OSC active layer. Favorable vertical phase separation and sufficient exciton dissociation interfaces can be simultaneously realized in such aggregation morphology via different processing technologies and strategies. High efficiencies of over 18% in ternary LBL device and 11.9% in LBL-processed module (11.52 cm 2 ) have been successfully achieved in recent works. Moreover, the unique merits of LBL structure in individual layer processing enable it a promising candidate for large-scale printing and further industrialization of OSCs. This perspective provides the recent advance of LBL OSCs with the focus on fabrication technologies and strategies for morphology control and also proposes the current thinking and perspective on LBL structures for future development.

Realizing 19.05% Efficiency Polymer Solar Cells by Progressively Improving Charge Extraction and Suppressing Charge Recombination

“…In most high-performance PSCs, geminate recombination is greatly reduced by obtaining a nanoscale interpenetration network and increasing the contact area between the donor and acceptor phases to overcome the limitation of exciton diffusion length and improve charge dissociation probability. [41,42] In this case, bimolecular recombination is the main mechanism for charge recombination, thus the competition between recombination and extraction of free charges determines the FF of PSCs. [39,[42][43][44] The bimolecular recombination arises from the flow resistance of charge carriers.…”

Recent Advances in Nonfullerene Acceptor‐Based Layer‐by‐Layer Organic Solar Cells Using a Solution Process

“…To access other results, including fullerene-based LbL OSCs, readers can refer to previous reviews where various materials including fullerene derivatives and their sequential LbL processing methods (i.e., vacuum deposition, hybrid spin casting/evaporation, stamping/lamination, and nanoimprinting) have been well-documented. [23][24][25][26][27][28] First, recent developments in PPHJ morphological control are summarized with a particular emphasis on vertical p-i-n (or n-i-p) phase separation by proper solvent selection, processing additives, protecting solvent treatment, thermal treatment, temperaturedependent aggregation structures, and ternary components. Second, the longer L D of NFAs (compared to fullerene derivatives) is discussed in terms of self-Förster resonance energy transfer (FRET) between acceptor molecules in the A phase to increase flexibility in the morphological control for high-performance LbL OSCs.…”

Highly efficient layer-by-layer large-scale manufacturing of polymer solar cells with minimized device-to-device variations by employing benzothiadiazole-based solid additives

“…20,21 This is due to limited donor/acceptor interfaces in the active layer, which is a setback for this approach. 22 Driven by its great potential for circumventing the aforementioned notorious issues related to the BHJ approach, the LBL approach has become increasingly popular anew as a promising alternative. 13,[23][24][25][26][27][28] Furthermore, several studies have pointed out that the superior stability and eco-friendly fabrication of LBL PSCs over BHJ PSCs might be more favorable for the industrial application of large-scale PSCs.…”

“…20,21 This is due to limited donor/acceptor interfaces in the active layer, which is a setback for this approach. 22…”