All‐Green Solvent‐Processed Planar Heterojunction Organic Solar Cells with Outstanding Power Conversion Efficiency of 16%

Abstract

Device engineering is an effective way to improve the photovoltaic performance of organic solar cells (OSCs). Currently, the widely used bulk heterojunction (BHJ) structure has problems such as material solubility limitations and the emerging pseudoplanar heterojunction (PPHJ) structure is also troubled by printing technology requirements. However, these issues can be solved by the reasonable application of traditional planar heterojunction (PHJ) structure. Herein, PM6:BO‐4F system is selected to prepare PHJ devices by combining sequential spin‐coating and orthogonal solvent strategy. In view of the good solubility of PM6 and BO‐4F in commonly used high‐boiling solvent chlorobenzene (CB) and green solvent tetrahydrofuran (THF), respectively, the PHJ devices are successfully prepared by using these two orthogonal solvents, achieving a power conversion efficiency (PCE) of 15.6%. On this basis, green nonhalogen reagent o‐xylene (O‐XY) is further used to process PM6. Due to the large polarity difference between O‐XY and THF, all‐green solvent‐processed PHJ devices are successfully fabricated and obtain an astonishing PCE of 16%. As far as it is known, it is the highest efficiency for PHJ OSCs. The results prove the huge research potential of PHJ structure and point out new direction for solving OSC materials compatibility, long‐term stability, and future commercial applications.

Quasiplanar Heterojunction All‐Polymer Solar Cells: A Dual Approach to Stability

“…Such a structure was defined previously as a quasiplanar heterojunction (Q-PHJ). [32][33][34][35] In the Q-PHJ structure, each component of the bilayer can be separately optimized, which facilitates better control of the active layer morphology and targeted analysis. This kind of structure achieves efficient exciton dissociation without adversely affecting the transports of the carriers in either the polymer donor or acceptor layers, and the carrier recombination could be reduced significantly.…”

Recent Advances in Nonfullerene Acceptor‐Based Layer‐by‐Layer Organic Solar Cells Using a Solution Process

“…After two pioneering works were reported, much effort has been made on optimizing processing solvents by several research groups. [30,32,33,[36][37][38][39]47,57,60,62] Yan et al demonstrated the importance of the chemical structures of the underlying polymer layer by using various processing solvents including CF, THF, toluene, chlorobenzene (CB), and ortho-xylene (o-XY). [34] The major limitation in the fabrication of LbL OSCs is the restriction in solvent selection for processing an NFA top layer; the underlying polymer film can be destroyed if NFAs are processed with nonorthogonal or highboiling-point solvents.…”

“…After two pioneering works were reported, much effort has been made on optimizing processing solvents by several research groups. [ 30,32,33,36–39,47,57,60,62 ]…”

Recent advances in small molecular design for high performance non-fullerene organic solar cells

“…The environmental impact of solution processed OSCs can be mitigated by introducing halogen-free solvents or green solvents during the fabrication processes. [33][34][35][36][37] Potential bottlenecks to low-cost OSC production lie largely in the cost of raw materials, especially for active layer materials. 38,39 Therefore, it is important to develop low-cost and efficient acceptor materials.…”