Efficient Polymer Solar Cells Having High Open-Circuit Voltage and Low Energy Loss Enabled by a Main-Chain Twisted Small Molecular Acceptor

Abstract

A new main-chain twisted small molecular acceptor with nonhalogenated end groups (i-IEICO) is designed and synthesized. In contrast to its planar analogue IECIO, i-IEICO possesses an obviously twisted backbone, leading to significant hypsochromic shift in film absorption, slight enhancement in solution extinction coefficient, and significantly elevated molecular energy level. Benefited from these features, i-IEICO is matched well with two wide band gap polymer donor materials (J52 and PBDB-T) both in absorption spectra and molecular energy levels. Relative to the planar-molecule IEICO-based devices, the open-circuit voltage (V OC ), short-circuit current density, and fill factor of the i-IEICObased devices are simultaneously improved, giving rising to a 10.48% (with J52) and 8.79% (with PBDB-T) power conversion efficiency, respectively. Moreover, J52:i-IEICO device exhibits a high V OC of 0.96 V accompanied by a small energy loss of 0.64 eV, which can be further improved to 1.01 V and 0.59 eV for the PBDB-T-based device. The obtained V OC of i-IEICO-based devices are among one of the highest values of either J52 or PBDB-T-based binary devices, suggesting the effectiveness of main-chain twisted strategy coupled with end-group modification to achieve highly efficient nonfullerene acceptors with low energy loss and high V OC .

Completely non-fused electron acceptor with 3D-interpenetrated crystalline structure enables efficient and stable organic solar cell

“…4a ). Obviously, the absorption spectra of A4T-21 show a large hypsochromic shift than that of A4T-16 and A4T-23, which mainly resulted from the twisted backbone of A4T-21 that suppressed the ICT effect 47 – 49 . The detailed absorption spectral parameters of A4T-16, A4T-21, and A4T-23 are provided as Supplementary Information (SI, Supplementary Table 1 ).…”

Isomerization Strategy of Nonfullerene Small‐Molecule Acceptors for Organic Solar Cells

“…The main‐chain twisted strategy have been employed to develop efficient isomeric SMAs with low voltage loss. [ 139,140 ] Gao and co‐workers obtained a nonplanar SMA (i‐IEICO) from the parent IEICO, by altering the attaching point of the IC terminus to the main chain. [ 139 ] In contrast to its planar analogue IEICO, i‐IEICO exhibits intensely hypsochromic shift in film absorption with enhanced molar extinction coefficient and upshifted energy levels.…”

“…[ 139,140 ] Gao and co‐workers obtained a nonplanar SMA (i‐IEICO) from the parent IEICO, by altering the attaching point of the IC terminus to the main chain. [ 139 ] In contrast to its planar analogue IEICO, i‐IEICO exhibits intensely hypsochromic shift in film absorption with enhanced molar extinction coefficient and upshifted energy levels. Along with J52 or PBDB‐T, i‐IEICO gave rise to PCEs of 10.48% or 8.79% with simultaneously improved V OC , J SC , and FF versus IEICO.…”

Thermally Durable Nonfullerene Acceptor with Nonplanar Conjugated Backbone for High‐Performance Organic Solar Cells

“…The twisted structures of i‐IEICO‐2F increase the bandgap, which is caused by the raised LUMO energy level. [ 26,27 ] The upshifted LUMO energy level of i‐IEICO‐2F is to get a better V OC in OSCs. The twisted main conjugated chain has increased the intramolecular steric hindrance, which decreased aggregation morphologies in films.…”

“…The twisted main conjugated chain has increased the intramolecular steric hindrance, which decreased aggregation morphologies in films. [ 26,27 ] The suitable LUMO energy levels and aggregation morphologies in J52:i‐IEICO‐2F blend film should have high thermal stability.…”