Recent Progress in Chlorinated Organic Photovoltaic Materials

Abstract

Metrics & MoreArticle Recommendations CONSPECTUS: Over the past few years, the development of new materials has contributed to rapid increases in the power conversion efficiencies (PCEs) of organic photovoltaic (OPV) cells to over 17%, showing great potential for the commercialization of this technology in the near future. At this stage, designing new materials with superior performance and low cost simultaneously is of crucial importance. Chlorinated materials are emerging as new stars with very high PCEs, creating a molecular design trend to replace the most popular fluorinated materials. For example, by using chlorinated non-fullerene acceptors, we recently got a record PCE of 17% for single-junction OPV cells. Firmly based on recent advances, herein we focus on the topic of chlorinated OPV materials, aiming to provide a guideline for further molecular design.In this Account, first, on the basis of most fundamental features of the Cl atom, we highlight the features of chlorinated materials compared with their fluorinated counterparts: (1) Chlorination is more efficient than fluorination in modulating the optical and electrical properties of OPV materials. In many cases, chlorinated materials show lower energy levels and broader absorption spectra than their fluorinated counterparts, which contribute higher output voltages and current densities in the resulting photovoltaic devices. (2) Cl has a large atomic size than F. On one hand, enhanced overlap of π electrons is beneficial for enhancing the intermolecular packing and crystalline property and thus improving the charge transport. On the other hand, if Cl is introduced inappropriately in the backbone or side chain, this feature will cause a more twisted π plane and larger steric hindrance, having negative impacts on the photovoltaic performance of the corresponding materials. (3) Importantly, chlorination is usually chemically cheaper in synthesis, which has the potential to decrease the material cost of OPV cells. Then, we provide a concise review of chlorinated OPV materials, including polymeric and small-molecule donors and non-fullerene acceptors. The photovoltaic performance in various types of OPV cells using chlorinated materials, such as single-junction, tandem, semitransparent, and indoor-light photovoltaic cells is also discussed. For instance, ultranarrow-band-gap chlorinated acceptors can be used to construct highly efficient color-semitransparent OPV cells, and the wide-band-gap chlorinated materials show great potential for fabricating indoor-light photovoltaic devices. Finally, we briefly discuss current questions related to chlorinated OPV materials and highlight the significance of chlorination in future development.

Miscibility‐Controlled Phase Separation in Double‐Cable Conjugated Polymers for Single‐Component Organic Solar Cells with Efficiencies over 8 %

“…[7i] It is also interesting to mention that PClBDB-T exhibited red-shift absorption spectra compared to that of PBDB-T-Cl, which should be due to the electronegative effect of Cl atoms. [18] Thef rontier energy levels of JP01 and JP02 were determined by cyclic voltammetry (CV) measurements, as shown in Figure 2b and the Supporting Information, Figure S3. Both of JP01 and JP02 have the similar lowest unoccupied molecular orbital (LUMO) levels with that of the NDI acceptors,while their highest occupied molecular orbital (HOMO) levels are slightly deeper than those of donor polymers (Figure 2b).…”

The Intrinsic Role of Molecular Mass and Polydispersity Index in High‐Performance Non‐Fullerene Polymer Solar Cells

“…[ 6,7,8 ] The NFA‐based PSCs have made significant improvements in efficiency, with certified power conversion efficiencies (PCEs) rapidly improving from 11% to extend to 17% over the past five years. [ 9,10,11,12 ] However, a number of works have shown that non‐fullerene PSCs also suffered from rapid performance degradation over time, particularly upon exposure to oxygen, light or elevated temperatures. [ 13,14,15,16 ] It can be seen that the development of highly efficient PSCs that show stable photovoltaic performance without adverse degradation remains a significant challenge in this field.…”

A Cost‐Effective, Aqueous‐Solution‐Processed Cathode Interlayer Based on Organosilica Nanodots for Highly Efficient and Stable Organic Solar Cells

“…significantly increased light absorption and reduced energy losses. [1][2][3][4][5][6] Recently, the PCE of single-junction OSCs is approaching the 18% milestone, exceeding the efficiency threshold expected for industrial viability. [7][8][9][10] Besides efficiency, long-term operational stability, such as thermal-and photostability, is a major concern for the practical application of OSCs.…”