Achieving Desired Pseudo-Planar Heterojunction Organic Solar Cells via Binary-Dilution Strategy

The sequential deposition process has demonstrated the great possibility to achieve a photolayer architecture with an ideal gradient phase separation morphology, which has a vital influence on the physical processes that determine the performance of organic solar cells (OSCs). However, the controllable preparation of pseudo-planar heterojunction (P-PHJ) with gradient distribution has not been effectively elucidated. Herein, a binary-dilution strategy is proposed, the PM6 solution with micro acceptor BO-4Cl and the L8-BO solution with micro donor PM6 respectively, to form P-PHJ film. This architecture exists good donor (D) and acceptor (A) vertical gradient distribution and larger D/A interpenetrating regions, which promotes exciton generation and dissociation, shortens charge transport distance and optimizes carrier dynamics. Moreover, the dilution of PM6 by BO-4Cl promotes the regulation of active layer aggregation size and phase purity, thus alleviating energy disorder and voltage loss. As a result, the P-PHJ device exhibits an outstanding power conversion efficiency of 19.32% with an excellent short-circuit current density of 26.92 mA cm-2, much higher than planar binary heterojunction (17.67%) and ternary bulk heterojunction (18.49%) devices. This research proves a simple but effective method to provide an avenue for constructing desirable active layer morphology and high-performance OSCs. Pseudo planar heterojunction (P-PHJ) is successfully fabricated by binary-dilution strategy (PM6 is mixed with micro acceptor BO-4Cl and L8-BO is mixed with micro donor PM6, respectively), which not only remains donor/acceptor (D/A) vertical distribution of binary planar heterojunction (P-BHJ), but gains larger D/A interpenetrating regions. The formation of ideal active layer morphology promotes excellent charge dynamics, and boosts the PCE of P-PHJ from 17.67% to 19.32%.image