Fibrillization of Non‐Fullerene Acceptors Enables 19% Efficiency Pseudo‐Bulk Heterojunction Organic Solar Cells

Abstract

The structural order and aggregation of non‐fullerene acceptors (NFA) are critical toward light absorption, phase separation, and charge transport properties of their photovoltaic blends with electron donors, and determine the power conversion efficiency (PCE) of the corresponding organic solar cells (OSCs). In this work, the fibrillization of small molecular NFA L8‐BO with the assistance of fused‐ring solvent additive 1‐fluoronaphthalene (FN) to substantially improve device PCE is demonstrated. Molecular dynamics simulations show that FN attaches to the backbone of L8‐BO as the molecular bridge to enhance the intermolecular packing , inducing 1D self‐assembly of L8‐BO into fine fibrils with a compact polycrystal structure. The L8‐BO fibrils are incorporated into a pseudo‐bulk heterojunction (P‐BHJ) active layer with D18 as a donor, and show enhanced light absorption, charge transport, and collection properties, leading to enhanced PCE from 16.0% to an unprecedented 19.0% in the D18/L8‐BO binary P‐BHJ OSC, featuring a high fill factor of 80%. This work demonstrates a strategy for fibrillating NFAs toward the enhanced performance of OSCs.

Recent Developments of Polymer Solar Cells with Photovoltaic Performance over 17%

“…[227,228] At present, the highest efficiency of the devices fabricated by SD method has been more than 19%. [216,[355][356][357] The fabrication process of device by SD method is shown in Figure 20a, and the schematic of the photovoltaic physic processes and the morphology along the vertical direction of the BHJ and pseudo-bilayer films are shown in Figure 20b,c. As can be seen, because of the longer exciton diffusion length and shorter charge transport path, exciton dissociation, charge extraction are effectively enhanced.…”

“…Finally, due to the synergistic effects of the multifunctional p-dopant of CS, CS/ PM6/Y6-based PSCs achieved an extraordinary PCE of 17.98%. Wang et al [356] utilized FN as acceptor additive to realize L8-BO with fibril-like morphology. They investigated that the L8-BO fibrils and LBL structure induce enhanced photon harvest and charge transport, and the fabricated devices reached an outstanding PCE of 19.00% and FF of 80.00%.…”

A nonfullerene acceptor with π-conjugation extended end groups to achieve enhanced photovoltaic performance

“…In the past decade, nonfullerene acceptors (NFAs) have attracted considerable attention in organic solar cells (OSCs) with the great stride of power conversion efficiencies (PCEs) to over 19%. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Recently, the rapid development of NFAs was mainly dominated by acceptor-donor-acceptor (A-D-A) type small-molecule acceptors (SMAs), [15][16][17][18][19][20][21][22][23][24][25][26][27] The main reason for great success of the A-D-A type SMAs lies in their easilytuned optoelectronic properties through simple chemical modification on the D and A units. [28][29][30][31][32][33][34][35][36][37] Elegant works have been reported, such as modulating the central units (D) with varied side chains to adjust the crystalline properties and modifying the terminal units (A) by introducing different functional groups to tune the light absorption range and molecular energy level, thus leading to a significant impact on the short-current density ( J sc ), open-circuit voltage (V oc ) and fill factor (FF).…”

BN‐Bond‐Embedded Triplet Terpolymers with Small Singlet–Triplet Energy Gaps for Suppressing Non‐Radiative Recombination and Improving Blend Morphology in Organic Solar Cells

“…[15][16][17] Thus, significant strides have been made in device performance with the power conversion efficiencies (PCEs) over 19% realized in state-of-theart OSCs. [11,[17][18][19][20][21][22][23][24][25][26] Nevertheless, the performance of OSCs still lags behind that of inorganic or perovskite solar cells due to the relatively large photon energy loss (E loss ). [27] As established, the E loss can be divided into radiative loss and nonradiative loss.…”