All-polymer organic solar cells offer exceptional stability. Unfortunately, the use of bulk heterojunction (BHJ) structure has the intrinsic challenge to control the side-chain entanglement and backbone orientation to achieve sophisticated phase separation in all-polymer blend. Here, we revealed that the P-iN structure can outperform the BHJ ones with a nearly 50% efficiency improvement, reaching a power conversion efficiency approaching 10%. This P-iN structure can also provide enhanced internal electric field and remarkably stable morphology under harsh thermal stress. We have further demonstrated generality of the P-iN structure in several other all-polymer systems. Considering the adjustable polymer molecular weight and solubility, the PiN device structure can be more beneficial for all-polymer systems. With the design of more crystalline polymers, the antiquated P-iN structure can further show its strength in all-polymer system by simplified morphology control and improved carrier extraction, becoming a more favorite device structure than dominant BHJ structure.

No abstract

Organic solar cells (OSCs) based on small molecular acceptors (SMAs) have made great development with a power conversion efficiency (PCE) over 16% due to the design of novel materials and advances in device preparation technology. This work fabricates two bulk‐heterojunction photovoltaic devices containing the same wide‐bandgap donor PM6, respectively, matched with popular Y6 and ITIC SMAs. The PM6:Y6‐based device achieves a much higher PCE of 15.21% than the PM6:ITIC‐based device of 9.02%. On the basis of comparisons of macroscopic performances in the quasistatic regime, transient absorption spectroscopy (TAS) is further performed to better understand the microscopic dynamics difference in charge separation processes between the two photovoltaic blends. According to the TAS results, the calculated hole transfer efficiency in PM6:Y6 is 71.4%, far greater than the efficiency of 13.1% in PM6:ITIC, demonstrating favorable charge separation at donor/acceptor interfaces via hole transfer channel in PM6:Y6. The favorable hole transfer in PM6:Y6 is accounted for by its better mutual miscibility between the donor and acceptor, and the formation of long‐lived delocalized intramoiety excimer state in the acceptor. These results highlight the important role of proper molecular design strategy with strong intermolecular coupling and beneficial film morphology on facilitating charge generation in OSCs adopting SMAs.

Current all polymer solar cells still suffer from low fill factors (FF) and short-circuit current density (J sc) compared with the conventional polymer/fullerene system. Herein in this work, devices using PTP8 as the electron donor and [70]PCBM as well as widely used polymer N2200 as the electron acceptor were systematically studied and compared. The major loss mechanisms in the all polymer solar cells were investigated to understand their relatively lower performance than the PTP8/fullerene system. By performing in-depth analysis on ultrafast transient transmission spectroscopy results, we estimated that in PTP8/N2200 device nearly half of the charges recombine geminately, which is confirmed as the major factor hindering the

A fiber-type perovskite solar cell is fabricated by wrapping a conducting carbon nanotube sheet onto a perovskite crystal-deposited strip electrode.