Efficient and Nonhalogenated Solvent-Processed Organic Solar Cells Enabled by Conjugated Donor–Acceptor Block Copolymers Containing the Same Benzodithiophene Unit

Abstract

Organic solar cells (OSCs) based on conjugated block copolymers (CBCs) have gained considerable attention owing to their simple one-pot solution process. However, their power conversion efficiencies (PCEs) require significant improvement. Furthermore, the majority of efficient CBC-based OSCs are processed using environmentally toxic halogenated solvents. Herein, we develop a new CBC (PBDB-T-b-PY5BDT) and demonstrate efficient and stable OSCs achieved by a halogen-free solution process. We design a (D1-A1)-b-(D1-A2)-type CBC (PBDB-T-b-PY5BDT) that shares the same benzodithiophene (BDT) units in donor and acceptor blocks. This alleviates unfavorable molecular interactions between the blocks at their interfaces. The PBDB-T-b-PY5BDT-based devices exhibit a high PCE (10.55%), and they show good mechanical, thermal, and storage stabilities. Importantly, we discuss the potential of our OSCs by preparing two different control systems: one based on a binary polymer blend (PBDB-T:PY5BDT) and another based on a conjugated random copolymer (CRC, PBDB-T-r-PY5BDT). We demonstrate that the photovoltaic performance, device stability, and mechanical robustness of the CBC-based OSCs exceed those of the binary all-polymer solar cells and CRC-based OSCs.

The Application of Y Series Acceptor-Based Double-Cable Polymers in Single-Material Organic Solar Cells

“…The introduction of noncovalent hydrogen bonds and dipole–dipole interactions to enhance intra/intermolecular interactions is beneficial for BHJ morphology stability. , Additionally, the partial formation of chemical bonds between molecules through optical and chemical cross-linking has been proven to limit morphology evolution to a certain extent in conventional BHJ active layers. , A more fundamental solution to improve morphology stability, and thereby enhance the photo, thermal, and mechanical stabilities of the device, is to chemically bond the donor and acceptor materials to synthesize a single-component material. , This is because, compared to the intermolecular heterojunction structures formed in two-phase or even multiphase blends, active layers consisting of single-component materials naturally form an intramolecular heterojunction structure due to the inclusion of donor and acceptor fragments within the same molecule, which significantly reduces the dependence of the charge transfer behavior on the active layer’s morphology. − Moreover, as the active layer consists of only one single-component material, the morphology evolution caused by the migration rate difference of various materials in the multiphase system under external driving force can be effectively avoided, thereby improving the stability of single-component OPVs (SCOPVs). , Recently, numerous single-component materials, mainly including molecular dyads, ,, double-cable conjugated polymers (DCCPs), − and conjugated block copolymers (CBCs), ,,− have been designed and synthesized to meet commercial application demands. For instance, Ma and Min et al successfully incorporated efficient donor (PBDB-T) and acceptor (Y series acceptor) segments into single-component materials through block copolymerization, achieving promising power conversion efficiencies (PCEs) of over 11%. ,, Subsequent optimizations of polymerization conditions and molecular structures led to the efficiency of CBCs-based SCOPVs surpassing 15%, further highlighting their application potential. , However, one major drawback of CBC materials synthesized by a one-pot polymerization method is their poor batch reproducibility, which hampers commercial production. , …”

“…50,51 However, one major drawback of CBC materials synthesized by a one-pot polymerization method is their poor batch reproducibility, which hampers commercial production. 52,53 On the contrary, the DCCPs offer a relatively well-defined structure and good batch reproducibility, making them the focus of this study. For example, Li et al developed a synthetic strategy that introduces acceptor pendants into the side chain of a high-performance polymer donor (PBDB-T), resulting in single-component materials with well-defined structures.…”

Regulating the Sequence Structure of Conjugated Block Copolymers Enables Large‐Area Single‐Component Organic Solar Cells with High Efficiency and Stability

“…[16][17] A few single-component materials have been developed in recent years, which are mainly based on three types: (1) molecular dyads with dual functions that connect D and A through flexible spacers; [11,[18][19][20] (2) conjugated polymers grafting A units as pendants in the polymer donor side chains; [21][22][23] (3) conjugated block copolymers (CBCs) connecting the polymer D-block and polymer A-block in one polymer chain. [13][14][24][25][26] However, the development of SCOSCs is far behind that of BHJ devices. This phenomenon can be attributed to two main factors.…”

“…Such CT channels can effectively weaken the dominant effect of D/A interfacial contact or phase size on charge transfer, thus overcoming the Coulomb binding energy of the CT state, and reducing energy loss [16–17] . A few single‐component materials have been developed in recent years, which are mainly based on three types: (1) molecular dyads with dual functions that connect D and A through flexible spacers; [11,18–20] (2) conjugated polymers grafting A units as pendants in the polymer donor side chains; [21–23] (3) conjugated block copolymers (CBCs) connecting the polymer D‐block and polymer A‐block in one polymer chain [13–14,24–26] …”

Regulating the Sequence Structure of Conjugated Block Copolymers Enables Large‐Area Single‐Component Organic Solar Cells with High Efficiency and Stability

“…[16][17] A few single-component materials have been developed in recent years, which are mainly based on three types: (1) molecular dyads with dual functions that connect D and A through flexible spacers; [11,[18][19][20] (2) conjugated polymers grafting A units as pendants in the polymer donor side chains; [21][22][23] (3) conjugated block copolymers (CBCs) connecting the polymer D-block and polymer A-block in one polymer chain. [13][14][24][25][26] However, the development of SCOSCs is far behind that of BHJ devices. This phenomenon can be attributed to two main factors.…”