Performance Optimization of Parallel‐Like Ternary Organic Solar Cells through Simultaneous Improvement in Charge Generation and Transport

Abstract

Ternary organic photovoltaic (OPV) devices with multiple light-absorbing active materials have emerged as an efficient strategy for realizing further improvements in the power conversion efficiency (PCE) without building complex multijunction structures. However, the third component often acts as recombination centers and, hence, the optimization of ternary blend morphology poses a major challenge to improving the PCE of these devices. In this work, the performance of OPVs is enhanced through the morphological modification of nonfullerene acceptor (NFA)-containing binary active layers. This modification is achieved by incorporating fullerenes into the layers. The uniformly dispersed fullerenes are sufficiently continuous and successfully mediate the ordering of NFA without charge or energy transfer. Owing to the simultaneous improvement in the charge generation and extraction, the PCE (12.1%) of these parallel-linked ternary devices is considerably higher than those of the corresponding binary devices (9.95% and 7.78%). Moreover, the additional energy loss of the ternary device is minimized, compared with that of the NFA-based binary device, due to the judicious control of the effective donor:acceptor composition of the ternary blends.

Combining Fused‐Ring and Unfused‐Core Electron Acceptors Enables Efficient Ternary Organic Solar Cells with Enhanced Fill Factor and Broad Compositional Tolerance

“…[53] Whereas in the parallel-like model, the V oc of the ternary device lies between those of the two binary devices. [23,53,68] In this case, the charges are generated independently at either the PBDB-TF: HC-PCIC or PBDB-TF:IT-M interface and transported through their corresponding material channels. In the parallel-like model, electrons generated in individual acceptors propagate through their corresponding acceptor channels to the cathode in parallel, without transferring between different acceptors (see Figure S5, Supporting Information).…”

“…As the V oc of two‐acceptor‐based systems tends to be fixed to the binary devices with the lowest V oc , the energetically favorable pathway for the electron is to transfer to the acceptor with a lower LUMO level . Whereas in the parallel‐like model, the V oc of the ternary device lies between those of the two binary devices . In this case, the charges are generated independently at either the PBDB‐TF:HC‐PCIC or PBDB‐TF:IT‐M interface and transported through their corresponding material channels.…”

High-Performance Ternary Organic Solar Cells Enabled by Synergizing Fullerene and Non-fullerene Acceptors

“…Hadmojo et al 56 investigated how the incorporation of [6,6]-phenyl-C 70 -butyric acid methyl ester (PC 70 BM) into the PBDTTPD-HT: ITIC binary OPV (PBDTTPD-HT, a D-A polymer containing benzo[1,2-b:4,5-b′] dithiophene and thieno [3,4-c]pyrrole-4,6-dione groups) affects the crystallinity of the binary blend. The PCE of 12.09% in the ternary OPV, compared with 9.95% in the binary-blend OPV, is attributed to the amendatory morphology of the ternary blend.…”

Non-fullerene acceptor alloy strategy enabling stable ternary polymer solar cells with efficiency of 17.74%

“…[5][6][7][8][9][10] To further enhance the performance of the devices in terms of efficiency and stability, the ternary strategy of preparing ternary organic solar cells (TOSCs) by introducing an extra donor or acceptor into the host binary system has been widely used and proved to be reasonable and effective. [11][12][13] According to the different intermolecular interactions among the three components in the blend system, the mechanism of performance enhancement of devices can be described by the following models: parallel, 14,15 charge transfer, 16,17 energy transfer 18,19 and alloy models, [20][21][22] and there are often more than two model mechanisms that work together in a TOSC, 23,24 which presents challenges in the choice of the third components. This is not only because it is necessary to carefully choose the appropriate mechanism model to improve the performance of a certain material system, but more importantly, the random introduction of the third component may destroy the charge transport channels and fine film morphology of the original binary system.…”