Design of a Fully Non‐Fused Bulk Heterojunction toward Efficient and Low‐Cost Organic Photovoltaics

Abstract

To modulate the miscibility between donor and acceptor materials both possessing fully non‐fused ring structures, a series of electron acceptors (A4T‐16, A4T‐31 and A4T‐32) with different polar functional substituents were synthesized and investigated. The three acceptors show good planarity, high conformational stability, complementary absorption and energy levels with the non‐fused polymer donor (PTVT‐BT). Among them, A4T‐32 possesses the strongest polar functional group and shows the highest surface energy, which facilitates morphological modulation in the bulk heterojunction (BHJ) blend. Benefiting from the proper morphology control method, an impressive power conversion efficiency (PCE) of approaching 16.0 % and a superior fill factor over 0.795 are achieved in the PTVT‐BT : A4T‐32‐based organic photovoltaic cells with superior photoactive materials price advantage, which represent the highest value for the cells based on the non‐fused blend films. Notably, this cell maintains ≈84 % of its initial PCE after nearly 2000 h under the continuous simulated 1‐sun‐illumination. In addition, the flexible PTVT‐BT : A4T‐32‐based cells were fabricated and delivered a decent PCE of 14.6 %. This work provides an effective molecular design strategy for the non‐fused non‐fullerene acceptors (NFAs) from the aspect of bulk morphology control in fully non‐fused BHJ layers, which is crucial for their practical applications.

Efficient and Thermally Stable Organic Solar Cells via a Fully Halogen-Free Active Blend and Solvent

“…The variance in the morphology change is part of the reason causing the stability issue of the OPV cell. 53 Further, Raman mapping was performed 54 for the blends after thermal aging (Figure 5d−f). Although it is difficult to accurately probe the D/A distribution change in blends, an overall lower change is recorded for the CS 2 -processed film, suggesting more stable D/A distribution/morphology in the blend and thus stabilized efficiency.…”