Conjugated Polymers Bearing Iridium Complexes for Triplet Photovoltaic Devices

Abstract

The aim of this work is to investigate the effect of incorporating an iridium complex into a π-conjugated polymer backbone on photovoltaic properties such as charge generation, power conversion efficiency and external quantum efficiency (EQE). Poly(9,9-dihexylfluorene-co-2-phenylpyridine) (1) and poly(9,9dioctylfluorene-co-tris(2-phenylpyridine) iridium (III))) (2) were synthesized using Suzuki polycondensation. Characterization was performed using NMR, UV-vis, photoluminescence, and time-resolved luminescence spectroscopy; gel permeation chromatography; elemental analysis; and photovoltaic devices. An increase in percent EQE for 2 over 1, from 1.1 to 10.3, is attributed to the formation of the triplet state in (2), and by inference, longer diffusion lengths of the triplet exciton, compared to the singlet exciton that is formed in (1).

Triplet Exciton and Polaron Dynamics in Phosphorescent Dye Blended Polymer Photovoltaic Devices

“…The MEH-PPV/C 60 bilayer photovoltaic device without PtOEP attained a short-circuit current ( J sc ) of 0.3 mA cm The enhanced photocurrent and power-conversion effi ciency in the PtOEP blended MEH-PPV/C 60 bilayer photovoltaic device can be attributed to the increased population of long-lived, mobile triplet excitons in the conjugated polymer, which is consistent with our PIA results and previously published data. [7][8][9][10][11][12][13][14][15] The long exciton diffusion length of the triplet excitons increases intersystem crossing effi ciency of MEH-PPV. Similar to our results, Cleave et al, reported that the enhanced triplet-exciton population of poly[(2-methoxy-5-(3,7-dimethyl)-octyloxy)-1,4-phenylenevinylene] (OC 1 C 10 -PPV) originated from the triplettriplet energy transfer from PtOEP to OC 1 C 10 -PPV.…”

“…[7][8][9][10][11][12][13][14][15] In general, these conjugated polymers with aromatic structure show weak spin-orbit coupling and thus limit the generation of triplet excitons. [ 16 ] Nonetheless, the tripletexciton density of these conjugated polymers could be enhanced by increasing the intersystem crossing (ISC) effi ciency [7][8][9] through spin-orbit coupling or triplet-triplet energy transfer [11][12][13][14] from the dopant to the conjugated polymer in the blended system.…”

Enhanced power conversion efficiency in iridium complex-based terpolymers for polymer solar cells

“…34 Furthermore, a 35 times higher of PCE was obtained in polymer/fullerene device by coordinating 50 mol% of Ir complex to conjugated backbone of poly(fluoreneco-phenylpyridine) due to the formation of the triplet state in Ir containing polymers. 41 Previously, we reported the conjugation of a triplet Ir complex (feed ratio: 1 mol%) to the famous high efficiency donor polymer PTB7. The PCE was found to be significantly increased compared to the Ir-free control polymer.…”

Study of intersystem crossing mechanism in organic materials

“…The use of organic materials in organic optoelectronic devices such as organic light emitting diodes (OLEDs), organic transistors, organic solar cells (OSCs) and organic-hybrid solar cells is an area of increasing research interest [1]. The advantages of using organic materials are reduced cost of fabrication, easy processing, large scale production and compatibility with flexible substrates [2][3][4].…”