Vacuum-Deposited Biternary Organic Photovoltaics

Abstract

Ternary blend organic photovoltaics (OPVs) have been introduced to improve solar spectral absorption and reduce energy losses beyond that of binary blend OPVs, but the difficulties in simultaneously optimizing the morphology of three molecular components result in devices that have generally exhibited performance inferior to that of analogous binary OPVs. Here, we introduce a small molecule-based biternary OPV comprising two individual, vacuum-deposited binary bulk heterojunctions fused at a planar junction without component intermixing. In contrast to previous reports where the open circuit voltage (V OC) of a conventional, blended ternary cell lies between those of the individual binaries, the V OC of the biternary OPV corresponds to one of the constituent binaries, depending on the order in which they are stacked relative to the anode. Additionally, dipole-induced energy-level realignment between the two binary segments necessary to achieve maximum efficiency is observed only when using donor–acceptor–acceptor′ dipolar donors in the photoactive heterojunctions. The optimized biternary OPV shows improved performance as compared to its two constituent binary OPVs, achieving a power conversion efficiency of 10.6 ± 0.3% under AM 1.5G 1 sun (100 mW/cm2) simulated illumination with V OC = 0.94 ± 0.01 V, a short circuit current density of 16.0 ± 0.5 mA cm–2, and a fill factor of 0.70 ± 0.01.

Understanding the structural and charge transport property relationships for a variety of merocyanine single-crystals: a bottom up computational investigation

“…[21][22][23][24][25] In particular for the field of vacuum-processable organic solar cells, merocyanines are among the best donor materials because they inherit high absorptivity and in some cases (vide infra) good hole mobility at rather small molecular size, as required for sublimation. 26,27 Liess et al demonstrated that moving from rigid/small to flexible/large side groups for a given p-conjugated merocyanine, the molecular packing varies from card-to slipped-stack arrangements, strongly affecting the optical and charge transfer properties. Card-and slipped-stack aggregates lead to H-and J-exciton couplings, respectively, causing a blue-or red-shift of the absorption band with respect to that of the monomer.…”

Oligomer‐Assisted Photoactive Layers Enable >18 % Efficiency of Organic Solar Cells

“…[1][2][3][4][5] A steady progression has been made in research on photoactive materials, interface engineering and device processing technology. [6][7][8][9][10] The most popularly studied OSCs usually consist of binary bulk heterojunction (BHJ) photoactive blends, where the spontaneous phase separation of the electron donor and electron acceptor provides sufficient interfaces for charge dissociation and continuous network for charge transport. In the past few years, non-fullerene acceptors (NFAs) have made rapid progress due to their easy-to-adjust photoelectric properties and strong absorption even in the near-infrared (NIR) region.…”

“…In past decades, solution‐processed organic solar cells (OSCs) have attracted great attention due to their light weight, low cost, high flexibility, roll‐to‐roll manufacturing and translucency [1–5] . A steady progression has been made in research on photoactive materials, interface engineering and device processing technology [6–10] . The most popularly studied OSCs usually consist of binary bulk heterojunction (BHJ) photoactive blends, where the spontaneous phase separation of the electron donor and electron acceptor provides sufficient interfaces for charge dissociation and continuous network for charge transport.…”

Asymmetric Non-Fullerene Small-Molecule Acceptors toward High-Performance Organic Solar Cells

“…Organic solar cells (OSCs) have been developed rapidly over the past few years benefiting from chemical structural diversity, mechanical flexibility, roll-to-roll large area printing, etc. − The classical active layers of single-junction OSCs usually consist of a p-type conjugated polymer as a donor and an n-type material (fullerene derivative or non-fullerene small molecule) as an acceptor . In the last two decades, fullerene derivatives have occupied a predominant position in electron acceptor materials due to their suitable electron affinity and isotropic electron transporting properties. − However, the power conversion efficiencies (PCEs) of the most perfect fullerene-based OSCs are limited to only ∼11%. , The demand for replacing fullerene in OSCs has led to the exploitation of non-fullerene small-molecule acceptors (NFSMAs).…”