2D Side‐Chain Engineered Asymmetric Acceptors Enabling Over 14% Efficiency and 75% Fill Factor Stable Organic Solar Cells

Abstract

The charge transport and morphology of active layers are key considerations for device performance and stability in organic solar cells (OSCs). Such properties can be fine-tuned via elaborate molecular design of fused-ring electron acceptors (FREAs), especially conjugation extension and side chain engineering. In this work, N-functionalized conjugation is explored in the design of high-efficient asymmetric FREAs. The twisting of N-conjugated side chains from backbone endows three FREAs with similar energy levels and light absorptions (≈850 nm edge). Their blends with PBDB-T exhibit high charge carrier mobility and ordered phase separation. Excitingly, IPT2F-TT based OSCs yield a champion power conversion efficiency (PCE) of 14.02% with a fill factor (FF) of 75.06%, outperforming PBDB-T devices with IPT2F-Th (12.52%, 71.20%), IPT2F-Ph (13.13%, 72.11%), and octylated IPT-2F (13.70%, 71.50%). The PCE over 14% and FF over 75% are among the highest values for 2D FREAs OSCs reported to date. More importantly, outstanding thermal stability and light soaking stability are observed with PCE over 12% maintained after thermal or light aging for 100 h. This work demonstrates N-conjugated FREAs design as an effective strategy to simultaneously improve the photovoltaic performance and device stability for the OSCs.

Alkyl‐Chain Branching of Non‐Fullerene Acceptors Flanking Conjugated Side Groups toward Highly Efficient Organic Solar Cells

“…[42,43] From a material design standpoint, side-chain engineering of NFAs is an effective strategy for regulating molecular interactions of the materials. [44][45][46][47] Specifically, the rational choices of the length, configuration, substitution positions, and chemical compositions of the side chains are the key to modulating the aggregation property of the materials and donor-acceptor compatibility. [48][49][50][51][52][53][54][55][56][57][58] However, such structural changes do not guarantee performance enhancement as they often have competing effects on device efficiencies.…”

A Simple Dithieno[3,2‐b:2′,3′‐d]pyrrol‐Rhodanine Molecular Third Component Enables Over 16.7% Efficiency and Stable Organic Solar Cells

“…[1] Benefited from the great innovation of acceptor-donor-acceptor (A-D-A) structure fused-ring electron acceptors (FREAs), OSCs have achieved the power conversion efficiency (PCE) over 17% for both single-junction and tandem devices. [2][3][4] In order to further enhance the performance and stability of OSCs to meet the needs of commercial application, researchers have developed successful device processing strategies (such as using processing additives, thermal annealing and vapor annealing [5][6][7] ) to modulate the blend morphologies in active layers.…”

Enhancing photovoltaic performance via aggregation dynamics control in fused‐ring electron acceptor

“…The planar configuration of molecular backbone facilitates molecular stacking and electronic coupling, while the out-of-plane orientations of side chains effectively restrain overaggregation. Modifications, such as extending molecular backbone, [24][25][26][27][28][29] reducing the steric hindrance of side chains [30][31][32][33][34] and introducing noncovalent interactions on backbone [35][36][37][38][39][40][41][42] and/or side chains [43][44][45][46][47][48][49] , can enhance intermolecular interactions and thus crystallinity.…”