Development of n-Type Porphyrin Acceptors for Panchromatic Light-Harvesting Fullerene-Free Organic Solar Cells

Abstract

The development of n-type porphyrin acceptors is challenging in organic solar cells. In this work, we synthesized a novel n-type porphyrin acceptor, PZn-TNI, via the introduction of the electron withdrawing naphthalene imide (NI) moiety at the meso position of zinc porphyrin (PZn). PZn-TNI has excellent thermal stability and unique bimodal absorption with a strong Soret band (300–600 nm) and weak Q-band (600–800 nm). The weak long-wavelength absorption of PZn-TNI was completely covered by combining the low bandgap polymer donor, PTB7-Th, which realized the well-balanced panchromatic photon-to-current conversion in the range of 300–800 nm. Notably, the one-step reaction of the NI moiety from a commercially available source leads to the cheap and simple n-type porphyrin synthesis. The substitution of four NIs in PZn ring induced sufficient n-type characteristics with proper HOMO and LUMO energy levels for efficient charge transport with PTB7-Th. Fullerene-free organic solar cells based-on PTB7-Th:PZn-TNI were investigated and showed a promising PCE of 5.07% without any additive treatment. To the best of our knowledge, this is the highest PCE in the porphyrin-based acceptors without utilization of the perylene diimide accepting unit.

Recent progress in organic–metal complexes for organic photovoltaic applications

“…11). 93 Por-A11 has excellent thermal stability, strong Soret band (300–600 nm) and weak Q band (600–800 nm). After blending with the low band gap polymer donor PTB7-Th, the weak Q-band of Por-A11 was supplemented, thus realizing the conversion of the panchromatic photon current balanced in the range of 300–800 nm.…”

Introducing Porphyrin Units by Random Copolymerization Into NDI-Based Acceptor for All Polymer Solar Cells

“…Inspired by this strategy, we are interested in introducing other chromophores into terpolymers to improve the absorption of polymers. Porphyrin as a type of chromophore has many remarkable features, like excellent light harvesters, easily finetuning optical and electronic properties and efficient electron transfer (Lee et al, 2018;Mahmood et al, 2018), which is in favor of polymer material performance improvement. Li and coworkers successfully combined porphyrin group with perylene bisimides to obtain efficient small-molecule acceptors (SMAs) with high extinction coefficient (over 2.0 × 10 5 cm −1 ) for OSCs (Zhang et al, 2017;Guo et al, 2018).…”