Efficient non-fullerene organic solar cells employing sequentially deposited donor-acceptor layersElectronic supplementary information (ESI) available: Hole and electron mobilities extracted from the SCLC, device stability over 3 weeks, EQE profile of the c-BHJ, and the sq-BHJ devices with different thicknesses of the PBDB-T layer, photocurrent generation versus the effective voltage, light-intensity dependent JSC and VOC, determination of the optical bandgap energy of NCBDT acceptor, EQE of EL

• Main Authors: Zhang, Jiangbin, Kan, Bin, Pearson, Andrew J, Parnell, Andrew J, Cooper, Joshaniel F. K, Liu, Xiao-Ke, Conaghan, Patrick J, Hopper, Thomas R, Wu, Yutian, Wan, Xiangjian, Gao, Feng, Greenham, Neil C, Bakulin, Artem A, Chen, Yongsheng, Friend, Richard H
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c8ta06860g

Non-fullerene acceptors (NFAs) have recently outperformed their fullerene counterparts in binary bulk-heterojunction (BHJ) organic solar cells (OSCs). Further development of NFA OSCs may benefit other novel OSC device structures that alter or extend the standard BHJ concept. Here, we report such a new processing route that forms a BHJ-like morphology between sequentially processed polymer donor and NFA with high power conversion efficiencies in excess of 10%. Both devices show similar charge generation and recombination behaviours, supporting formation of similar BHJ active layers. We correlate the ∼30 meV smaller open-circuit voltage in sq-BHJ devices to more substantial non-radiative recombination by voltage loss analysis. We also determine the exciton diffusion length of benchmark polymer PBDB-T to be 10 ± 3 nm. Our results demonstrate high-efficiency OSC devices using sequential deposition method and provide new opportunities to further improve performance of state-of-the-art OSCs. A new fabrication method via sequentially depositing donor and acceptor layers can push the power conversion efficiency of organic solar cells based on non-fullerene acceptors to over 10%.