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

In addition to efficiency, stability is another key factor in developing organic solar cells. The quasiplanar heterojunction (Q-PHJ) structure, combining two pure layers as major and tiny nanoscale bulk heterojunction (BHJ) at interface, demonstrates superior device stability compared with BHJ devices. In this contribution, the polymer donor, PBQx-H-TF, and configurationally defined polymeric acceptor, PBTIC-gamma-TSe are synthesized and used to fabricate bilayer devices by orthogonal solvents, the corresponding Q-PHJ all-polymer solar cells (all-PSCs) deliver reliable stability with high efficiency. An encouraging PCE of 15.77% is achieved, which is the highest one among Q-PHJ all-PSCs with real-bilayer structure. There is a major improvement over the 13.91% PCE in the BHJ device, and the carrier transport performance is improved substantially following the reduction of recombination in the Q-PHJ all-PSCs. Benefiting from the bilayer morphology, the stability of Q-PHJ all-PSCs has been greatly enhanced over that of the BHJ devices. The charge recombination process is also more serious in the aging BHJ compared with the aging Q-PHJ all-PSCs. This work inspires the application of Q-PHJ in the preparation of high-efficient all-PSCs, but also provides guidance on the improvement of device stability from a dual approach of material and device engineering aspects.