Müller Jolanda Simone, Comí Marc, Eisner Flurin, Azzouzi Mohammed, Herrera Ruiz Diego, Yan Jun, Attar Salahuddin Sayedshabbir, Al-Hashimi Mohammed, Nelson Jenny
Department of Physics and Centre for processable Electronics, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, United Kingdom.
Department of Arts and Sciences, Texas A&M University at Qatar, Education City, P.O. Box 23874, Doha, Qatar.
ACS Energy Lett. 2023 Jul 14;8(8):3387-3397. doi: 10.1021/acsenergylett.3c00943. eCollection 2023 Aug 11.
We investigate the charge-generation processes limiting the performance of low-offset organic bulk-heterojunction solar cells by studying a series of newly synthesized PBDB-T-derivative donor polymers whose ionisation energy (IE) is tuned via functional group (difluorination or cyanation) and backbone (thiophene or selenophene bridge) modifications. When blended with the acceptor Y6, the series present heterojunction donor-acceptor IE offsets () ranging from 0.22 to 0.59 eV. As expected, small decrease nonradiative voltage losses but severely suppresses photocurrent generation. We explore the origin of this reduced charge-generation efficiency at low through a combination of opto-electronic and spectroscopic measurements and molecular and device-level modeling. We find that, in addition to the expected decrease in local exciton dissociation efficiency, reducing also strongly reduces the charge transfer (CT) state dissociation efficiency, demonstrating that poor CT-state dissociation can limit the performance of low-offset heterojunction solar cells.
我们通过研究一系列新合成的PBDB-T衍生物供体聚合物来探究限制低偏移有机本体异质结太阳能电池性能的电荷产生过程，这些聚合物的电离能（IE）通过官能团（二氟化或氰化）和主链（噻吩或硒吩桥）修饰进行调节。当与受体Y6混合时，该系列呈现出0.22至0.59 eV的异质结供体-受体IE偏移（）。正如预期的那样，小的偏移会降低非辐射电压损失，但会严重抑制光电流的产生。我们通过光电和光谱测量以及分子和器件级建模相结合的方式，探索在低偏移情况下这种电荷产生效率降低的根源。我们发现，除了局部激子解离效率的预期降低之外，降低偏移还会强烈降低电荷转移（CT）态解离效率，这表明不良的CT态解离会限制低偏移异质结太阳能电池的性能。
