Improving Device Efficiency of Polymer/Fullerene Bulk Heterojunction Solar Cells Through Enhanced Crystallinity and Reduced Grain Boundaries Induced by Solvent Additives

Abstract

The power conversion efficiency of a device incorporating a crystalline polymer/fullerene thin film improves from 5% to 7.3% – a relative increase of 45% – when an additive, diiodohexane (DIH), is present during processing. The DIH‐processed active layer exhibits substantially enhanced polymer crystallinity and smaller fractal‐like fullerene clusters.

Morphology Evolution in High‐Performance Polymer Solar Cells Processed from Nonhalogenated Solvent

“…Shown in Figure 4 a, for the TMB film, dark irregularly shaped structures with a size up to ≈500 nm were observed, which are attributed to PC 71 BM‐rich domains 38, 39. For the CB film, PC 71 BM‐rich domains with size scales from ≈200 to ≈400 nm were also observed.…”

Alkyl side-chain branching point effects in thieno[3,4-c]pyrrole-4,6-dione copolymers

“…Stille polymerisation whilst versatile and reliable affords number-average molecular weights (M n ) below 10 kDa (Table 1), as has been observed with those reported for similar copolymers. [26,29] It may be possible to achieve higher molecular weights by direct heteroarylation polymerisations. [28] Optical properties.…”

“…Use of a bi(alkyl)thiophene aids solubility, though the tail-totail configuration of the alkyl chains is vital in preserving crystallinity. [21] Such alkylated TPD-2T polymers have achieved efficiencies as high as 7.3% in BHJ photovoltaic cells and field-effect transistors exhibit hole mobilities as high as 0.6 cm 2 /V s. [22][23][24][25][26][27] In addition, these polymers have recently been reported with both economic and green syntheses. [28,29] Here, we report a novel and efficient synthesis of the TPD unit facilitating late-stage alkylation by haloalkanes and direct C-H activation polymerisation.…”

Recent Advances in P-Type Conjugated Polymers for High-Performance Solar Cells

“…To promote solubility, the branched -EH chain of the TPD unit was used. M n of P32 was 9.7 kDa with a PDI of 1.4 ( [80] reported [82]. To increase the coplanarity of the conjugated backbone and enhance crystalline, Wei et al further incorporated the TT unit into the Th/TPD based copolymer.…”