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The Balance between Energy Transfer and Exciton Separation in Ternary Organic Solar Cells with Two Conjugated Polymer Donor
摘要： Ternary strategy as a straightforward way for organic solar cells (OSCs) to improve the device performance attracts many interests in the field. The ternary strategy usually focuses on processing the third light-absorbing material owning a complementary absorption to the binary system. However, studying the third component with similar absorption spectra to the binary counterpart is equally essential to understand the in-depth mechanism of the performance improvement from the third component. In this work, we filled up this blank and derived a type of ternary device consisting of two conjugated polymer donor materials of PTB7-Th and PffBT4T-2OD and non-fullerene acceptor material of IEICO-4F. The average PCE value of the optimized ternary device reached 12.1%, which is around 16% higher than its PTB7-Th:IEICO-4F binary counterpart. Even the third component of PffBT4T-2OD containing a similar absorption spectrum with PTB7-Th, it was found that the Jsc increase contributes to the primary performance enhancement. Further investigations indicate that the Jsc increase in the optimized ternary device mainly came from the improved light absorption ability, current extraction process, charge transport process, and suppressed non-radiative recombination. Moreover, there is a balance found between the exciton separation process and the energy transfer process when optimizing ternary blend ratios. The optimized ternary device is suspected to reach this balance point and thus exhibits the enhancement in device performance. Morphology investigation reveals that the addition of PffBT4T-2OD can tune the morphology and increase the crystallinity in the active layer. The optimized ternary blend shows a well-mixed donor and acceptor morphology with small domain size and slightly increased crystallization, which further explained its best device performance.
关键词： non-fullerene,energy transfer,exciton separation,organic solar cells,ternary,crystallization,conjugated polymer
更新于2025-09-23 15:21:01
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An inverted BiI3/PCBM binary quasi-bulk heterojunction solar cell with a power conversion efficiency of 1.50%
摘要： The use of toxic Pb hinders the widespread applications of lead halide perovskite solar cells, sparking an upsurge effort to develop lead-free solar cells. This work reports a facile low-temperature solution processed bismuth triiodide (BiI3)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) binary quasi-bulk heterojunction (BQ-BH) solar cell. The BiI3 and PCBM layers are innovatively utilized as the electron donor and acceptor to form a BQ-BH that promotes the separation of the excitons. The effective separation of excitons at the BiI3/PCBM BQ-BH is experimentally confirmed by the Kelvin probe force microscopy. An optimized inverted BiI3/PCBM BQ-BH solar cell can achieve a champion power conversion efficiency of 1.50% with a record short-circuit current density of 8.76 mA cm-2. The findings of this work confirm that the separation of excitons can be effectively promoted by inducing a suitable electron donor/acceptor type of BQ-BH, providing a new means to enhance the performance of BiI3-based solar cells.
关键词： electron acceptor,quasi-bulk heterojunction,exciton separation,solar cells,BiI3
更新于2025-09-23 15:21:01