In‐depth probe of researching interfacial charge transfer process for organic solar cells: A promising bisadduct fullerene derivatives acceptor

Abstract

The charge transfer (CT) mechanism at the donor/acceptor (D/A) interface plays an irreplaceable role in the photoelectric conversion of efficient bulk‐heterojunction (BHJ) organic solar cells (OSCs), which affects the resulting competition between charge separation and charge recombination. Extensive CT studies have preferred monoadduct fullerene derivatives (M60, M70) due to their unique spherical geometry with fewer factors to consider. However, the effect of carbon cage size, substituent group properties and the number of CT properties have not been much discussed. Here, sulfur‐containing bisadducts (B60, B70) were selected to explore whether they are also suitable for CT research like classical monoadducts. Using density functional theory and time‐dependent density functional theory, interface stacking configuration, key parameters relevant to CT states, charge separation, and recombination rates were determined to confirm the characteristics of B60 and B70 as a good acceptor applied to interfacial research. This work points to the CT mechanism along the route of DA → D*A → D+A− through a theoretical analysis and also provides candidates for the theoretical interface photoelectric process in BHJ OSCs: bisadduct fullerene derivatives as good acceptor materials.

Charge transfer regulated by domain differences between host and guest donors in ternary organic solar cells

“…The molecular structures of monomers were optimized with the PBE0/6-31G(d,p) level, 43,44 and the ternary blends were optimized using CAM-B3LYP/6-31G(d,p) with D3 dispersion to characterize the long-range CT excitation properties. 45,46 All density functional theory calculations were performed in the Gaussian 09 program package. 47 MD simulations were used to visualize the unoccupied regions under the microscopic topography of the blends.…”

Computational Design of Crescent Shaped Promising Nonfullerene Acceptors with 1,4-Dihydro-2,3-quinoxalinedione Core and Different Electron-withdrawing Terminal Units for Photovoltaic Applications

“…In recent years, acceptors have been at the forefront of organic-based photovoltaic research and development. − So far, two types of acceptors have been extensively studied, and they are fullerene acceptors (FAs) and nonfullerene acceptors (NFAs). Over the past few years, fullerene and its derivatives such as 6,6-phenyl-C61-butyric acid methyl ester (PC 61 BM), 6,6-phenyl-C71-butyric acid methyl ester (PC 71 BM), and indene-C 60 bisadduct (ICBA) played significant roles in boosting organic photovoltaic performance as they all have a high electron affinity, unique spherical geometry, and good isotropic charge transport ability. − However, their difficult and expensive synthesis, limited structural tunability, weak absorption spectra, and thermal instability become major bottlenecks for improving device performance. − Alternatively, nonfullerene acceptors, namely 3,9-bis­(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis­(4-hexylphenyl)-dithieno­[2,3-d:2′,3′-d′]-s-indaceno­[1,2-b:5,6-b′]­dithiophene (ITIC), 2,2′-((2 Z ,2′ Z )-((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno­[1,2-b:5,6-b′]­dithiophene-2,7-diyl)­bis­(methanylylidene))­bis­(3-oxo-2,3-dihydro-1 H -indene-2,1-diylidene))­dimalononitrile (IDIC), and 2,2′-((2 Z ,2′ Z )-((12,13-bis­(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]­thiadiazolo­[3,4- e ]­thieno­[2″,3″:4′,5′]­thieno­[2′,3′:4,5]­pyrrolo­[3,2-g]­thieno­[2′,3′:4,5]­thieno­[3,2- b ]­indole-2,10-diyl)­bis­(methanylylidene))­bis­(5,6-difluoro-3-oxo-2,3-dihydro-1 H -indene-2,1-diylidene))­dimalononitrile (Y6) have several advantages over fullerene acceptors such as easy synthesis, tunable energy levels via simple structural modifications, extended optical absorption profiles, and favorable charge transfer at low energetic driving force while maintaining a good open-circuit voltage to short-circuit current density trade-off. − Nonfullerene acceptors typically contain different donor (D) and acceptor (A) blocks as core and terminal units, along with (possibly) π-bridging units with arrangements such as A-D-A, A-π-D-π-A, and A 2 -DA 1 D-A 2 . Different design strategies of core, terminal and bridging units, as well as their arrangements within the molecule, have led to promising NFAs for photovoltaic applications. ,, In particular, structural tuning of core and terminal (or end) groups has been reported to be a promising strategy for building potential NFAs. − For example, indacenodithiophene (IDT) is one of the most widely used cores in the NFA backbone.…”

Charge Transfer Mechanisms Regulated by the Third Component in Ternary Organic Solar Cells

“…Therefore, three types of D 1 -D 2 /A T-OSCs reported experimentally were selected as research objects (Figures and S1): P3HT/SMPV1/PC 71 BM T-OSCs with imbalanced M n and different backbones for D 1 and D 2 , P3HT/PCPDTBT/PC 61 BM T-OSCs with equivalent M n and different backbones, and DR3TBDTT/DR3TBDTT-E/PC 71 BM T-OSCs with equivalent M n and similar backbones (The full names of the molecules are listed in Table S1). Molecular dynamics (MD) simulations of the D 1 -D 2 /A models were performed under constant pressure (1 bar) and temperature (298 K) with three-dimensional periodic boundary conditions, as shown in Figure S2. , (See the Supporting Information for the details of the functionals, simulation process, and results. − ) It is worth noting that here the focus is only on the face-on stacking pattern, considering its favorable charge dissociation proved by recent works . Since the position of D 2 affects the operating mode in T-OSCs, the molecular packing morphologies of the amorphous active layers were obtained (Figure S5) and further classified manually into three groups, namely, D 1 /D 2 /A, D 1 /A/D 2 , and A/D 1 /D 2 (Figure ).…”