Achieving high-efficiency thick-film bulk heterojunction (BHJ) organic solar cells (OSCs) with thicknessindependent power conversion efficiencies (PCEs) in a wide thickness range is still a challenge for the roll-to-roll printing techniques. The concept of diluting the transport sites within BHJ films with insulating polymers can effectively eliminate charge trapping states and optimize the charge transport. Herein, we first adopted the concept with insulating polypropylene (PP) in the efficient non-fullerene system (PM6:Y6) and demonstrated its potential to fabricate thick-film OSCs. The PP can form an insulating matrix prior to PM6 and Y6 within the BHJ film, resulting in an enhanced molecular interaction and isolated charge transport by expelling Y6 molecules. We thus observed reduced trap state density and improved charge transport properties in the PP-blended device. At around 300 nm, the PM6:Y6:PP device enjoys a high PCE of 15.5% and achieves over 100% of the efficiency of the optimal thin-film device, which is significantly improved compared to the binary PM6:Y6 counterpart. This research promotes an effective strategy with insulating polymers and provides knowledge of commercial production with response to the roll-to-roll technique demands.

Organic molecule and inorganic nanocrystal hybrids have become a promising platform for photon energy conversion. Although surface energetics modification was proven effective in promoting triplet energy transfer, singlet energy transfer and charge transfer have been barely investigated. Here, we systematically clarify the photophysical dynamics of charge, singlet exciton, and triplet exciton among the energy conversion process based on hybrids of rubrene and Cd2+-adsorbed PbS nanocrystals. It is found that a considerable amount of charges in rubrene molecules can be transferred to cation-induced surface states in ~2 ps time scale with high efficiency to trigger a delayed biexciton effect, which provides a novel approach to uncover the intermediate role of nanocrystal surface sates. For triplet exciton, strong interaction with surface states is investigated with a recycling energy transfer around 14% efficiency, which is found insensitive to changes in nanocrystal surface energetics. As a result, the maximum photoluminescence lifetime of PbS nanocrystals was enhanced by about 38%. This work reveals the neglected photo-physical dynamics in the transfer process between organic molecules/inorganic nanocrystals and validates the capability of surface state in sensitization of organic charges and excitons.