Boosting the Performance of Non-Fullerene Organic Solar Cells via Cross-Linked Donor Polymers Design

Abstract

In general, cross-link is applied into conjugated polymers for improving stability of organic solar cells, but its effect on the photovoltaic performance received little attention. Particularly, cross-linked conjugated polymers with poor solubility show strong aggregation in bulk-heterojunction thin films, resulting in low charge generation efficiencies and hence poor performance in solar cells. Herein, we were able to develop a series of cross-linked conjugated polymers as electron donor for application in organic solar cells with a non-fullerene acceptor IT-4F, in which the photovoltaic performance and morphological stability in a nitrogen environment could be significantly improved. The polymers contain an electron-deficient thieno­[3,4-c]­pyrrole-4,6-dione (TPD) unit alternated with two-dimensional benzodithiophene, in which a four brominated-TPD monomer was applied into polymerization to obtain cross-linked polymers. All these cross-linked polymers perform identical absorption spectra, energy levels, and hole mobilities with the non-cross-linked polymer, but their photovoltaic performance was different. The cross-linked polymer containing 3% cross-linker as electron donor realized a high power conversion efficiency of 12.18% in non-fullerene organic solar cells, while the polymer donor without cross-linker only provided a low PCE of 7.56%. The greatly enhanced performance in cross-linked polymer solar cells was due to optimized nanophase separation with crystalline and small domain in blended thin films, resulting in efficient charge generation. Our results demonstrate that by rationally designing cross-linked conjugated polymers, it is possible to simultaneously obtain high performance and morphological stability in a nitrogen environment in organic solar cells, enabling their great potential application in large-area devices.

Bithieno[3,4-c]pyrrole-4,6-dione-Mediated Crystallinity in Large-Bandgap Polymer Donors Directs Charge Transportation and Recombination in Efficient Nonfullerene Polymer Solar Cells

“…Recently, Jang and co-workers have reported the PCE of ∼10% for the fullerene-free BHJ PSCs made with a TPD-based polymer donor and an ITIC acceptor . A meticulous cross-link strategy was used to tune the BHJ morphology phase separation, and the TPD polymer donor-based BHJ solar cells exhibited promising performance with PCE of ∼12% . A few studies indicate that polymers combining TPD motifs along the backbone may be a class of potential high-performing LBG polymer donor candidates for efficient nonfullerene PSCs as long as the energetic, morphological, and charge transport parameters are all taken into consideration.…”

“…27 A meticulous cross-link strategy was used to tune the BHJ morphology phase separation, and the TPD polymer donor-based BHJ solar cells exhibited promising performance with PCE of ∼12%. 28 polymers combining TPD motifs along the backbone may be a class of potential high-performing LBG polymer donor candidates for efficient nonfullerene PSCs as long as the energetic, morphological, and charge transport parameters are all taken into consideration. TPD dimer (bithieno [3,4-c]pyrrole-4,6-dione, BiTPD) is a derivative of TPD but has a larger planar skeleton and stronger electron-withdrawing ability than that of TPD, making it a potential useful planar building block for efficient polymer donors and acceptors.…”

Improving Electron Transport in a Double-Cable Conjugated Polymer via Parallel Perylenetriimide Design

“…However, in our recent study, we find that the polymer PTPDBDT has strong aggregation tendency in thin films, which can be suppressed via a cross-linking strategy. 59 From this aspect, we speculate that the large BPTI could hamper the aggregation/crystallization of the PTPDBDT backbone, and therefore provide a better hole and electron transport in PTPDBPTI-based SCOSCs.…”

Progress in Materials, Solution Processes, and Long‐Term Stability for Large‐Area Organic Photovoltaics

“…[ 145 ] Cross‐linking of conjugated polymers is another strategy to preserve morphological stability. [ 147 ] Cross‐linked polymer solar cells blended with the nonfullerene acceptor IT‐4F showed enhanced performance due to optimized nanophase separation with crystalline and small domains, resulting in efficient charge generation. A small amount of additives with hydrogen bonding can be introduced to improve the thermal stability of OPVs.…”