dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
Sci Rep. 2013;3:2073. doi: 10.1038/srep02073.
It is common knowledge that poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend, a prototype system for bulk heterojunction (BHJ) solar cells, consists of a network of tens of nanometers-large donor-rich and acceptor-rich phases separated by extended finely intermixed border regions where PCBM diffuse into P3HT. Here we specifically address the photo-induced dynamics in a 10 nm thin P3HT/PCBM blend that consists of the intermixed region only. Using the multi-pass transient absorption technique (TrAMP) that enables us to perform ultra high sensitive measurements, we find that the primary process upon photoexcitation is ultrafast energy transfer from P3HT to PCBM. The expected charge separation due to hole transfer from PCBM to P3HT occurs in the 100 ps timescale. The derived picture is much different from the accepted view of ultra-fast electron transfer at the polymer/PCBM interface and provides new directions for the development of efficient devices.
众所周知，聚（3-己基噻吩）（P3HT）/[6,6]-苯基-C61-丁酸甲酯（PCBM）共混物是体异质结（BHJ）太阳能电池的原型体系，它由数十纳米大小的施主富相和受主富相的网络组成，这些相由延伸的精细混合边界区域隔开，其中 PCBM 扩散到 P3HT 中。在这里，我们特别研究了仅由混合区域组成的 10nm 厚 P3HT/PCBM 共混物中的光致动力学。使用多通瞬态吸收技术（TrAMP），我们能够进行超高灵敏度测量，我们发现光激发后的主要过程是 P3HT 到 PCBM 的超快能量转移。由于 PCBM 向 P3HT 的空穴转移而导致的预期电荷分离发生在 100ps 时间尺度内。所得的图像与聚合物/PCBM 界面上超快电子转移的公认观点大不相同，为高效器件的发展提供了新的方向。
