High‐Efficiency Nonfullerene Organic Solar Cells with a Parallel Tandem Configuration

Abstract

In this work, a highly efficient parallel connected tandem solar cell utilizing a nonfullerene acceptor is demonstrated. Guided by optical simulation, each of the active layer thicknesses of subcells are tuned to maximize its light trapping without spending intense effort to match photocurrent. Interestingly, a strong optical microcavity with dual oscillation centers is formed in a back subcell, which further enhances light absorption. The parallel tandem device shows an improved photon-to-electron response over the range between 450 and 800 nm, and a high short-circuit current density (J ) of 17.92 mA cm . In addition, the subcells show high fill factors due to reduced recombination loss under diluted light intensity. These merits enable an overall power conversion efficiency (PCE) of >10% for this tandem cell, which represents a ≈15% enhancement compared to the optimal single-junction device. Further application of the designed parallel tandem configuration to more efficient single-junction cells enable a PCE of >11%, which is the highest efficiency among all parallel connected organic solar cells (OSCs). This work stresses the importance of employing a parallel tandem configuration for achieving efficient light harvesting in nonfullerene-based OSCs. It provides a useful strategy for exploring the ultimate performance of organic solar cells.

Recent Advances of Organic Solar Cells with Optical Microcavities

“…Jen and Wang et al conducted further research on parallel tandem solar cells with MC structure. They designed a kind of intermediate transparent electrode (ITE) with sterling performance, with the structure of modified PEDOT:PSS (m‐PEDOT:PSS)/PEDOT:PSS/Ag/Au/MoO 3 . The ITE has good transparency and conductivity, can form favorable Ohmic contact with the front and back sub‐cells, and provides the solvent protection ability in the manufacturing process.…”

Versatile Ternary Approach for Novel Organic Solar Cells: A Review

“…Nevertheless, it remains difficult to cover the solar spectrum fully with a single organic donor mixed with an acceptor due to the intrinsic light absorption properties of organic materials, and this also imposes limitations on PCE improvement . Tandem OSCs comprising at least two active layers with complementary absorption spectra and parallel OSCs that connect two single OSCs in series can overcome the limitation of a narrow absorption window with a single active layer . However, the process of fabricating tandem or parallel OSCs is complicated, and the cost of such devices is very high, both of which limit large‐scale production.…”

Advances in Non‐Fullerene Acceptor Based Ternary Organic Solar Cells

“…On the other hand, as organic molecules typically present low charge carrier mobility, BHJ films usually retain very thin (as low as 100 nm) to gain efficient charge collection, unfortunately, which cannot fully capture all incident sunlight in their absorption ranges . Therefore, tandem structure composed of multiple active layers with complementary optical absorptions has been introduced in order to enhance light‐harvesting capability, and thereby increase the device efficiencies . Although tandem OSCs successfully overcome the absorption limitation of binary blend OSCs, the complexity in device fabrication and difficulty in intermediate layer processing bring serious technical challenges.…”