Achieving 19% Power Conversion Efficiency in Planar‐Mixed Heterojunction Organic Solar Cells Using a Pseudosymmetric Electron Acceptor

Abstract

flexibility, and tunable optical transparency, which are advantageous for applications in building-integrated photovoltaic (PV) and wearable electronics compared with conventional inorganic cells. [1][2][3][4][5] To achieve high efficiency, it is essential to develop suitable donor (D) and acceptor (A) materials that can be easily processed into a finely phase-separated morphology in active layer with low energy loss (E loss ) in OSCs. [6][7][8][9] Recently, the vibrant progress made on nonfullerene acceptors (NFAs), [10,11] especially the Y-series NFAs, [12] with facilely tailored chemical structures and precisely tuned bandgap, energy levels, and crystallization properties, has enabled OSCs to achieve very high power conversion efficiencies (PCEs) ≈19%. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] The bulk-heterojunction (BHJ) architecture-based devices prepared from mixing D and A in solution is the most widely adopted method for depositing photoactive layer and have successfully increased the PCE of single-junction OSCs to 19% recently. [31] Another emerging strategy is to deposit neat D and A materials A record power conversion efficiency (PCE) of over 19% is realized in planarmixed heterojunction (PMHJ) organic solar cells (OSCs) by adopting the asymmetric selenium substitution strategy in making a pseudosymmetric electron acceptor, BS3TSe-4F. The combined molecular asymmetry with more polarizable selenium substitution increases the dielectric constant of the D18/ BS3TSe-4F blend, helping lower the exciton binding energy. On the other hand, dimer packing in BS3TSe-4F is facilitated to enable free charge generation, helping more efficient exciton dissociation and lowering the radiative recombination loss (ΔE 2 ) of OSCs. As a result, PMHJ OSCs based on D18/BS3TSe-4F achieve a PCE of 18.48%. By incorporating another mid-bandgap acceptor Y6-O into D18/BS3TSe-4F to form a ternary PMHJ, a higher open-circuit voltage (V OC ) can be achieved to realize an impressive PCE of 19.03%. The findings of using pseudosymmetric electron acceptors in enhancing device efficiency provides an effective way to develop highly efficient acceptor materials for OSCs.

Side Chain Length and Interaction Mediated Charge Transport Networks of Non-Fullerene Acceptors for Efficient Organic Solar Cells

“…As an emerging renewable energy technology, organic solar cells (OSCs) have given rise to extensive attention owning to their advantages including lightweight, mechanical-flexibility, and solution-processing ability. − Over the past several years, the maximum power conversion efficiency (PCE) of OSCs has exhibited rapid growth, with a PCE of 11% in 2015 to over 20% in 2022. − This inspiring breakthrough can be attributed to the arise of new non-fullerene acceptors (NFAs) as well as physical control of their aggregation states that are optimal for power conversion. − …”

Over 17% efficiency all-small-molecule organic solar cells based on an organic molecular donor employing a 2D side chain symmetry breaking strategy

“…S35, ESI†). 49,50 Compared to BTR-Cl, which has an ε r of 2.91 ± 0.22a much higher ε r s values of 3.42 ± 0.17 and 3.68 ± 0.23 were recorded for TB and TB-F, respectively, which suggest that more efficient exciton dissociation can be achieved in their pure domains. 51 These ε r variations may result from the increased dipole moment and changed electrostatic distribution of molecules endowed by the asymmetric 2D side chains strategy, which could facilitate the optimization of exciton generation and diffusion properties.…”

Sequential Processing Enables 17% All-Polymer Solar Cells via Non-Halogen Organic Solvent

“…In addition to their extremely thin active layer, e.g., ~100 nm, OSCs have many features that traditional photovoltaics do not have, such as flexibility [ 2 , 3 ], semitransparency [ 4 ], low-cost printing production [ 5 ], etc., and are considered one of the most promising next-generation PV technologies for commercialization [ 6 , 7 ]. In the near future, the market entry of OSCs will strongly depend on the improvement of their photovoltaic conversion efficiency (PCE) and stability [ 8 , 9 ]. In the past few years, the most successful strategy to improve the PCE has involved alternating the materials used in the active layer.…”