Bi Sheng, Ouyang Zhongliang, Shaik Shoieb, Li Dawen
Key Laboratory for Precision and Non-traditional Machining Technology of the Ministry of Education, Dalian University of Technology, No. 2 Linggong Rd, Dalian, 116024, P.R. China.
Department of Electrical and Computer Engineering, Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, AL, 35487, USA.
Sci Rep. 2018 Jun 22;8(1):9574. doi: 10.1038/s41598-018-27868-2.
In organic bulk heterojunction solar cells (OSCs) donor-acceptor vertical composition profile is one of the crucial factors that affect power-conversion efficiency (PCE). In this simulation study, five different kinds of donor-acceptor vertical configurations, including sandwich type I and type II, charge transport favorable, charge transport unfavorable, and uniform vertical distribution, have been investigated for both regular and inverted OSC structures. OSCs with uniform and charge transport favorable vertical composition profiles demonstrate the highest efficiencies. High PCE from charge transport favorable configuration can be attributed to low recombination because of facilitated charge transport in active layer and collection at electrodes, while high PCE from uniform structure is due to sufficient interfaces for efficient exciton dissociation. OSCs with sandwich and charge transport unfavorable structures show much lower efficiencies. The physical mechanisms behind simulation results are explained based on energy band diagrams, dark current-voltage characteristics, and comparison of external quantum efficiency. In conclusion, experimental optimization of vertical composition profile should be directed to either uniform or charge transport favorable vertical configurations in order to achieve high-performance OSCs.
在有机本体异质结太阳能电池（OSC）中，给体-受体垂直组成分布是影响功率转换效率（PCE）的关键因素之一。在本模拟研究中，针对常规和倒置OSC结构，研究了五种不同类型的给体-受体垂直构型，包括三明治I型和II型、有利于电荷传输型、不利于电荷传输型以及均匀垂直分布型。具有均匀和有利于电荷传输的垂直组成分布的OSC表现出最高的效率。有利于电荷传输构型的高PCE可归因于活性层中电荷传输的促进和电极处的收集导致的低复合，而均匀结构的高PCE则归因于有效激子解离的足够界面。具有三明治和不利于电荷传输结构的OSC效率要低得多。基于能带图、暗电流-电压特性以及外量子效率的比较，解释了模拟结果背后的物理机制。总之，为了实现高性能的OSC，垂直组成分布的实验优化应针对均匀或有利于电荷传输的垂直构型。
